Wisteria floribunda; photo by Jack Stane via Wikimedia
For decades, it has been clear that deliberate introduction of plant species for cultivation plays a central role in the early stages of bioinvasion by plants (and associated insects, plant pathogens, earthworms … even vertebrates. Viz. coqui frogs in Hawai`i.)
Repeatedly over the two plus decades since Sarah Reichard demonstrated this role of ornamental horticulture (see Reichard and White 2001 and Mack 2000), new studies have provided corroborative details. Publications during the past two years show the risks we are still accepting in the United States. Will we act to protect our environment?
Fertakos and Bradley (2024) found that species were likely to establish if they were introduced to as few as eight locations. However, introduction history was not a strong predictor of an established species’ ultimate invasive success. They suggest that other characteristics, like plant traits and local-scale processes (e.g., interspecific interactions), may better predict whether a plant becomes invasive.
Kinlock et al. (2025) also found that plant species that were cultivated longer or were sold by more catalogs were more likely to have “naturalized”. This conclusion was based on analysis of the behavior of nearly 4,000 species sold in nursery and seed catalogs in the continental United States over 200 years. Nearly 41% of these species naturalized somewhere in the “lower 48” states. Unfortunately, they do not discuss what proportion of these species are truly damaging invaders.
Neither Fertakos and Bradley (2024) nor Kinlock et al. (2025) mention the concept of a lag between a species’ establishment and recognized symptoms of invasiveness. Has this concept been repudiated?
Evans et al. (2024) were focused on analyzing which regions of the eastern United States are likely to suffer the worst plant invasions under climate change. In this context, they worry that people will assist non-native plant species’ movement to newly suitable habitats. Evans et al. urge prioritizing for state regulation species in the ornamental trade that are projected to remain or become abundant under the new climate conditions. They say we Americans are poorly prepared to take this action, however, because plant sales are so poorly regulated and only 10% of land managers in eastern North America monitor for new invasive taxa. They say this is because the managing agencies lack of funding and personnel. After 2025’s losses of programs, appropriations, grants, and staff, this deficit is probably worse – not just for federal agencies but also the many state, local, and volunteer programs that have been supported by federal funding.
Beaury et al. (2024) investigated whether plant species recognized as invasive are sold in the same locations as where they are invasive. They found that half of the 89 species named as invasive were sold by a nursery within 21km of an observed record of invasion. The authors say that data gaps mean that these findings underestimate the number of species sold near locations of documented invasions. They warn that at least 25 species are sold by one or more nurseries located in an area that is currently unsuitable for those species, but that will become more suitable for invasion as temperatures warm. Like Evans et al. (2024), they urge proactive regulation to limit these species’ spread.
burning bush Euonymus, Japanese honeysuckle, & English ivy invading a bottomland hardwood site in Fairfax County, Virgina; photo by F.T. Campbell
U.S. Regulatory response is completely inadequate
Beaury et al. (2023) call for regulating the nursery trade in a manner consistent with the scope of the horticultural trade – sales by both e-commerce and brick and mortar stores go to customers far outside a specific state’s jurisdiction. Despite the interstate nature of the trade, sales of horticultural plants are regulated primarily by state governments. Even when a state does restrict the sale of a specified list of invasive plants, the regulations are outdated, tend to include only a few weeds that plague agriculture rather than those that invade natural systems, or are irregularly enforced. The result is a checkerboard of places where a species may legally be offered for sale next to places where that sale is prohibited. Finally, the regulations are reactive; they rarely include plants in anticipation of their spread to new areas. Beaury et al. (2023) call this as a missed opportunity to reduce the likelihood of ornamental escapes.
Evans et al. (2024) also note that online plant sales are relatively unregulated, and state regulations are inconsistent.
Under the Constitution, the appropriate entity for regulating interstate commerce is the federal government. The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service is responsible for populating and managing the federal noxious weed list. Unfortunately, APHIS lists only those taxa that qualify as quarantine pests under the definition of that term in the International Plant Protection Convention (IPPC) Glossary of Phytosanitary Terms. This means that the taxon is either not yet present in the United States or, if present, is not widely distributed and is being officially controlled. Under these criteria, the federal noxious weed list is required to exclude nearly all the invasive plant species sold by the nursery trade.
To counter this enormous regulatory failure, many associations – native plant societies, regional or state invasive plant councils, etc. – publish their own lists of invasive plants. They often encourage their members and the public to either avoid planting these species voluntarily or to plant predominantly native plants. Also, these stakeholders urge nurseries to halt sales of invasive species voluntarily. Dr. Douglas Tallamy points out that even non-invasive, non-native plants disrupt food webs.
These voluntary efforts have yielded some success. But they have not resulted in adequate protection for our ecosystems.
Will Americans choose to invigorate the regulatory system? At a minimum, can we urge neighboring states to adopt a regional approach? More difficult, but also more effective, would be to persuade Congress to strengthen APHIS’ invasive plant regulations to outlaw interstate sales of at least those species documented to be invasive.
Cortadera selloana; picture by Alex Borland via PublicDomainPictures.net
Do you have other suggestions?
SOURCES
Beaury, E.M., J.M. Allen, A.E. Evans, M.E. Fertakos, W.G. Pfadenhauer, B.A. Bradley. 2023. Horticulture could facilitate invasive plant range infilling and range expansion with climate change. BioScience 2023 0 1-8 https://doi.org/10.1093/biosci/biad069
Evans, A.E., C.S. Jarnevich, E.M. Beaury, P.S. Engelstad, N.B. Teich, J.M. LaRoe, B.A. Bradley. 2024. Shifting hotspots: Climate change projected to drive contractions and expansions of invasive plant abundance habitats. Diversity and Distributions 2024;30:4154
Fertakos, M.E. and B.A. Bradley. 2024. Propagule pressure from historic U.S. plant sales explains establishment but not invasion. Public? doi: 10.1111/ele.14494.
Fridley, J.D., P.J. Bellingham, D. Closset-Kopp, C.C. Daehler, M.S. Dechoum, P.H. Martin, H.T. Murphy, J. Rojas- Sandoval, D. Tng. 2025. A general hypothesis of forest invasions by woody plants based on whole-plant carbon economics.
Kinlock, N.L., D.W. Adams, W. Dawson, F. Essl, J. Kartesz, H. Kreft, M. Nishino, Jan Pergl, P. Pyšek, P. Weigelt and M. van Kleunen. 2025. Naturalization of ornamental plants in the United States depends on cultivation and historical land cover context. Ecography 2025: e07748 doi: 10.1002/ecog.07748
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
I, and many others, have given much attention to the emerald ash borer (EAB), a species in the Agrilus genus. This attention is deserved. In 30 years EAB has spread from then-localized infestations in Michigan and Ontario to natural and urban ash ecosystems across North America. The EAB is spreading in Europe, too.
coast live oak killed by GSOB at Heisey State Park, San Diego County, California; photo by F.T. Campbell
We have paid far less attention to a second Agrilus, the goldspotted oak borer (GSOB), Agrilus auroguttatus. In roughly 30 years, the GSOB infestation has become the primary agent of oak mortality across much of southern California, an area of roughly 37 million square miles. This is bigger than the combined land areas of West Virginia, Maryland, and Delaware.
While the number of trees killed has generally expanded slowly, there have been periods of explosive growth. For example, annual mortality was estimated to have reached 40,000 trees in 2017. The officially documented cumulative total is over 142,000. At least one scientist, Joelene Tamm, considers this number to be a significant underestimate; she estimates the true number of trees killed as probably close to 200,000. As she explains (see here), the USFS’ Aerial Detection Surveys is not very effective at capturing mortality within fragmented urban landscapes, narrow riparian corridors, or when the target species have sprawling canopies (as oaks do).
Ravaged oak forests grow on five mountain ranges. People losing valuable resources and paying to manage the invasion include
U.S. taxpayers — three National forests have lost oaks; a fourth Forest is on the brink;
Residents of California – trees killed in at least four State parks, 10 County parks, and two major private reserves;
Native Americans on at least five reservations
City dwellers and property owners: up to 300,000 coast live oak trees live in built-up sections of just one heavily infested city, Los Angeles.
areas vulnerable to GSOB
This damage is almost guaranteed to spread in the future. Three oak species host GSOB: coast live oak (Quercus agrifolia), California black oak (Q. kelloggii), and canyon live oak (Q. chrysolepis). The ranges of black and canyon live oak stretch north along the Coastal Mountain Range and the foothills of the Sierra Nevada Mountain Range into southwest Oregon. The range of coast live oak reaches Mendocino County. A risk assessment concluded that GSOB could invade all these regions. Among urban areas, Santa Barbara faces the highest risk because of the large number of oaks in its urban forest. While this county has not yet been invaded by GSOB, the beetle is now in adjacent Ventura County – although at the other end of the county.
GSOB is transported to new locations primarily by the movement of firewood. This means of human-assisted spread almost certainly explains its initial introduction to from southeastern Arizona to California – in eastern San Diego County – in the 1990s. (See here for the explanation why it is unlikely that the beetle would have spread to California through natural dispersal.) It is blamed for the establishment of numerous disjunct populations that propelled its spread. These outbreaks led to recognition of invasions in additional counties in new counties in 2012, 2014, 2015, 2018, and 2024.
Death of these trees causes numerous ecological impacts. Oaks provide food, habitat, and climate control for hundreds of species. Oak mortality also increases the probability and severity of wildfire. The few natural enemies, including woodpeckers and some parasitoids, are not keeping GSOB populations in check. Urban trees provide important ecological services, including shade which reduces energy use and expense associated with air conditioning; they also reduce storm water runoff. Larger trees – those preferred by GSOB – provide more of these services. Dead oaks not only deny people of these services; they also demand prompt removal to prevent them falling on people or structures; this is done at considerable expense.
GSOB invasions are now known to be present in six counties: San Diego, Orange, Los Angeles, Riverside, San Bernardino, and Ventura. Since the state has opted out of leading management of the beetle (see below), coordination of these many players presents significant challenges on top of the usual difficulties that hinder most U.S. efforts to reduce threats from non-native forest insects and pathogens:
Detection of outbreaks occurs years after the pest’s actual introduction. Locations of disjunct outbreaks are difficult to predict. They fuel more rapid dispersal.
The host species are not important commercial timber sources, so key forest stakeholders do not act – despite the tree species’ great ecological importance.
USDA APHIS does not engage because GSOB has become a non-native tree-killing organism in a single state (although it was introduced from a separate state – Arizona).
Problems more specific to GSOB are:
Some authorities dismiss this invasion because the beetle is native in one U.S. state.
California State agencies and the National Park Service have not taken effective action to control movement of the principal vector – in this case, firewood.
Fortunately, a broadening alliance of locals is trying to fill the gaps. These efforts are truly encouraging. Concerned individuals and organizations in Southern California have put together a broad coalition that works to ensure an outbreak-wide response. Participants include staffers in the USDA’s Forest Service and Natural Resources Conservation Service; the U.S. Bureau of Indian Affairs; CalFire; California Department of Conservation; State parks; agencies of four counties; community Fire Safe councils; regional conservation agencies; several Resource Conservation districts; various Tribes and Tribal Nations; and University of California extension. In some counties, there are also geographically-focused coordinating bodies.
Money is scarce, but somehow they manage to carry out detection and monitoring, vigorous outreach and education projects, and — at some sites — treatment of vulnerable trees and removal of “amplifier” trees. Teams working under the umbrella of this coalition have developed GSOB-killing treatments for logs (firewood); search for tools to increase survey efficacy; investigate the area-wide impact of the beetle, and its interaction with drought. Scientists have also explored possible biocontrol agents in the species’ native habitat in Arizona. However, the two parasitic wasps found there are already present in California, where their parasitism rates are much lower.
Some of the participants have been willing to “go political” in search of resources and official actions.
Might this coalition be a model for addressing other pests?
As if GSOB were not a sufficient threat to California’s oaks, several other non-native pests are already established in the state. These include at least seven pests and pathogens:
three shot hole borers — polyphagous, Kuroshio, and Euwallaceae interjectus; they attack at least Coast live oak (Quercus agrifolia), Engelmann oak (Quercus engelmannii), Valley oak (Quercus lobata), Canyon live oak (Quercus chrysolepis)
Mediterranean oak borer; attacks valley oak (Quercus lobata); blue oak (Q. douglasii); and Oregon oak (Q. garryana).
acute oak decline (bacterium Rahnellav victoriana);
At least GSOB, SOD, and two of the shot hole borers have received official “zone of infestation” (ZOI) designation by the California Board of Forestry. This designation enables
the Board to specify required pest mitigation measures for any timber harvest;
the Board & the CalFire authority to enter private properties to abate pest problems if necessary.
calls attention to the presence of the pest within the Zone and provides the Department with a talking point to motivate landowners & land managers to address problems caused by the pest in question.
The southern California coalition includes these other bioinvaders in its efforts.
Lobbying by members of the coalition – especially John Kabashima – resulted in the state legislature providing funds to address the invasive shot hole borers (see here and here.)
Although oak decline was observed in eastern San Diego County as early as 2002, and a GSOB was caught in a survey trap in 2004, the beetle’s role in killing these oaks was identified only in 2008. This detection was followed by the discovery of disjunct infestations were detected in towns surrounded by National forests first in Riverside County (2012), then in Orange County (2014) and Los Angeles County (2015). Outbreaks in San Bernardino County were detected in 2018 – although the beetle had probably been present since 2013. The LA County populations continued to spread, despite management efforts. The obvious danger prompted neighboring Ventura County to initiate surveillance trapping in 2023. Sure enough, this sixth county found its first outbreaks in 2024. Most of the initial outbreaks have been on private land bordering or surrounded by National forests.
black oak in Cleveland National Forest killed by GSOB; photo by F.T. Campbell
Responses: State, County, and Federal
The California Department of Food and Agriculture (CDFA) classifies GSOB as a level “B” pest. Pests in this category are known to cause economic or environmental harm; however, their distribution is considered to be “limited”. Efforts to eradicate, contain, suppress, or control the species are at the discretion of individual county agricultural commissioners.
There is some outside support – usually because of the link to increased fire danger. Grants from the National Forest Foundation have enabled local Fire Safe councils, CalFire, and the Inland Empire Resource Conservation District (IERCD) to conduct surveys and in some cases removal of amplifier trees in Riverside and San Bernardino counties. However, the funds no longer support the earlier practice of spraying at-risk trees.
County-by-County
In Orange County, a coalition of academics from the University of California and scientists with CalFire and USFS are testing various pesticide applications and efficacy of removing heavily infested trees. The county has adopted an Early Detection Rapid Response Plan.
Since the first detection of GSOB in Los Angeles County in 2015, authorities have removed nearly 10,000 “amplifier” trees. Because the Santa Monica Mountains are home to 151,000 oaks, LA County Agricultural Commissioner of Weights and Measures, the Santa Monica Mountain Resource Conservation District (RCD), Los Angeles National Forest and UC Cooperative Extension established a joint “Bad Beetle Watch” program with Ventura County. The program is training agency personnel, tree professionals, and recreationists to detect GSOB. A state agency – Mountains Recreation and Conservation Authority – is managing two outbreaks in the Santa Monica Mountains. The Los Angeles County Fire / Forestry Division is surveying the oak-dense San Fernando Valley and Santa Susana Mountains after GSOB was found nearby. The Los Angeles County Regional Planning agency will target oak-dense communities with advocacy for oak woodland health and warnings not to move firewood.
Most encouraging, the Los Angeles County Board of Supervisors is considering declaring a local or state emergency related to the risk of the spread of GSOB in the County and to the Santa Monica Mountains.
Ventura County began trapping at green waste facilities and campgrounds in 2023. Now that GSOB has been detected, several agencies — CalFire, Ventura County Fire, Ventura County Resource Conservation District, California Coastal Conservancy, Rivers and Mountains Conservancy, Santa Monica Mountains Conservancy, Mountains Recreation and Conservation Authority, Ojai Valley Land Conservancy, Ventura Fire Safe Council, Ojai Valley Fire Safe Council as well as the state lands commission and Los Padres National Forest – are gearing up educational programs focused on the risk of GSOB spread to additional areas. The non-governmental organization Tree People helped to spark this effort. Efforts are under way to fund and formalize a regional coalition, with collaboration from California Department of Conservation, CAL FIRE, and UC Agriculture and Natural Resources.
Despite the damage to state parks and the clear nexus with firewood, the California State Park agency encourages – but does not require – campers and picnickers to purchase certified clean firewood on site from camp hosts.
Affected Tribal Lands
Among affected Native American reservations, the La Jolla Band of Luiseño Indians has already removed almost one thousand large coast live oak trees in the Tribe’s campground; another thousand trees must be removed in coming years. Since 2019, the Tribe has been applying contact insecticides annually on 200 to 300 trees. In addition, the Tribe is planting seedlings and conducting research in partnership with UC Riverside, San Diego State University, and UC Irvine. Obtaining funds to develop management capacity is a constant challenge.
A second tribe, the Pala Band of Mission Indians, began a systematic survey of its lands in 2022. At that time, they found a light infestation in coast live oaks and some dispersal. Hundreds of dead trees are visible from highways bordering the Mesa Grande, Santa Ysabel, and Los Coyotes reservations. Even reservations that have no oaks on their land are affected because tribal members harvest acorns as a culturally important food.
Private Reserves
Two private reserves in Orange County responded aggressively to arrival of GSOB. The Irvine Ranch Conservancy started active management immediately after detection of GSOB in 2014. Their efforts – annual surveys, treating lightly infested trees, and removing heavily infested or “amplifier” trees – have paid off: by 2023, only 21 of 187 coast live oaks surveyed had new exit holes – and in most cases only one or two. Weir Canyon is considered a successful control program.
Managers of the California Audubon Starr Ranch Sanctuary began monitoring for GSOB by 2016. No GSOB were detected until 2023. Difficult terrain impedes survey and response. Orange County Fire Authority hired contractors to remove amplifier trees and treat others. Monitoring continues.
Responses by Federal Agencies
The Angeles, Cleveland, and San Bernardino National forests all have extensive and evolving management plans for GSOB. Actions include annual surveys, tree removal and/or treatment, regulating concessionaires’ sources of firewood, and restricting wood harvest permits. Each forest has also partnered with appropriate counties, NGOs, FireSafe councils, and Resource Conservation districts to expand outreach, monitoring, and management. Many of the efforts are centered around communities within and adjacent to National Forest boundaries and recreation sites, since they are the main source of GSOB ingress. Success is not guaranteed. Six years of applying contact insecticides to high-visit recreation sites did not prevent establishment of at least two new infestations on private inholdings in Trabuco Canyon (Cleveland National Forest).
The fourth National Forest in southern California, Los Padres NF – which lies partially in Ventura and Los Angeles counties – has not yet found any GSOB but it is preparing. The Forest conducted a forest health training with heavy emphasis on GSOB in spring 2024 and is in the process of creating its own monitoring and management plan to include preemptive evaluation of environmental concerns under the National Environmental Protection Act (NEPA) and planning.
GSOB management is an important facet of the National Forest Wildfire Crisis Strategy implemented by all four National Forests in southern California. Challenges include steep and inaccessible terrain; wilderness designations; designation of sensitive habitat for wildlife, ecological, or heritage sites; and the sheer amount of land managed. Despite this, the forests have expanded their efforts each year. At the National Plant Board meeting in July, Sky Stevens reported that GSOB is one of the priority pests being addressed by the Forest Health Protection program. However, this program has been severely downsized by the Trump Administration, so its ability to assist is unclear. Budgets for individual National forests are also in limbo.
The Issue of Firewood
Several National parks located in California contain important oak forests and woodlands that are also at risk, especially given the importance of firewood in spreading the pest. Yosemite and Kings Canyon-Sequoia National parks and other campgrounds in the Sierra Nevada receive large numbers of campers from the Los Angeles area.
A 2014 National Park Service resource guide for firewood management summarized federal plant pest regulations at the time. These have since changed because emerald ash borer is no longer federally regulated. The guidance advised Park staff to define their park’s forest resources, keep abreast of present and potential forest pest species, and act to manage risks from potentially infested firewood. Park concessioners are required to purchase and sell only locally grown and harvested firewood in accordance with state quarantines. However, California does not have relevant quarantines for either firewood as a commodity or for oak pests specifically. The websites of Yosemite and Kings Canyon-Sequoia National parks ask people not to bring firewood obtained from a source more than 50 miles from the parks.
California does participate in the Firewood Scout program, Firewoodscout.org which advises campers on local sources from which to purchase their wood. Statewide, a consortium of several agencies, academia, and non-government agencies operates a “Buy It Where You Burn It” campaign that promotes this message with the public and firewood vendors.
Funding is a perpetual problem. No agency, not even CalFire, is funded to remove amplifier trees. The agency does use its crews to remove GSOB infested trees when they can. Most funding for treating infested trees comes from competitive grants awarded by CalFire or National Forest Foundation.
In 2012 the California Board of Forestry and Fire Protection (which is appointed by the Governor) officially designated a Zone of Infestation (ZOI) for GSOB. The Zone has been expanded as the infestation spread. The Zone of Infestation formally recognizes GSOB as a threat to California’s woodland resources and seeks to raise awareness among the governor, legislature, and public. The action was also intended to foster collaborative efforts to manage the beetle.
Joelene Tamm, Vice Chair of the California Forest Pest Council Southern California Committee (CFPC), is leading an initiative to address wildfire risks from invasive pests, including GSOB, South American Palm Weevil, and the invasive shothole borers. She presented a pest update with potential solutions to the California Board of Forestry (BOF) and followed up with a presentation to the BOF Resource Protection Committee, which is now identifying responsive actions. The Governor’s Wildfire Task Force is considering incorporating the topic into future meetings. The initiative’s core message is that the state must address the root cause of pest proliferation, as treating the symptom of wildfire alone is an unsustainable strategy (Tamm, pers. comm. August 2025).
For more details and sources, visit the GSOB brief here.
[I could find no recent updates about a third Agrilus, the soapberry borer (Agrilus prionurus), which is established in Texas from Mexico and was earlier said to kill the western soapberry (Sapindus saponaria var drummondii). It is established in at least 42 counties, reaching from the Dallas-Ft. Worth area to the Rio Grande valley.
soapberry borer; photo by Texas A&M Forest Service
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
The National Plant Board (NPB) represents the state officials responsible for preventing the introduction, establishment, and spread of invasive species called “plant pests” – including insects and pathogens that attack our native flora and invasive plants. The NPB has just held its 2025 meeting, on which I report here.
Coming to the Mid-Atlantic: NPB 2026 Annual Meeting
The next annual meeting will be in Alexandria, Virginia at the end of July 2026.I have attended these annual meetings since 2006 and always find them worth my time. They provide a wonderful opportunity to interact with the state and federal officials responsible for managing invasive plants and plant pests, and to assess regulatory issues. Contact me for more information.
The agendas focus on practical topics, such as science and technology tools, changes in APHIS policies or practices, and progress in cooperation among relevant federal agencies (i.e., the U.S. Department of Agriculture and the Department of Homeland Security’s Bureau of Border Protection) and with the states. While agricultural pest issues are stressed, tree-killing pests also get attention. Sometimes invasive plants are also discussed. The Board’s state representatives seek ways to coordinate their efforts both at these meetings and throughout the year.
Issues in the host location are part of the focus. Next year, that will be the Mid-Atlantic. The meeting is being co-hosted by the departments of Agriculture of Virginia, Maryland, Washington, D.C., and Delaware.
I expect that there will be opportunities for presenting concerns of non-governmental organizations – at least through staffed display tables and possibly other activities. I hope the many conservation organizations that have a Washington, D.C., presence will consider participating.
In Honolulu: NPB 2025 Annual Meeting
NPB’s 2025 Annual Meeting in Honolulu focused to some extent on the unique aspects of agriculture and introduced pests on remote Pacific islands. (Guam was co-host.) This blog reports on current efforts by federal and state authorities to counter bioinvasions there and around the country.
I took advantage of the meeting to visit the “Big Island” of Hawai`i to see for myself the impact of rapid ‘ōhi‘a death and enjoy the native flora (for example, the hapu tree fern – below). I posted another blog reporting what I learned there.
native Hawaiian tree ferns & ʻōhiʻa; photo by F.T. Campbell
Federal
In an earlier blog, I outlined the Administration’s proposed cuts to staff of the U.S. Department of Agriculture (USDA) and contradictory actions by Congress in the annual appropriations bills.
As that blog makes clear, the work of USDA’s Animal and Plant Health Inspection Service (APHIS) is viewed much more positively by the Trump Administration than is the USDA Forest Service. While APHIS’ funding is much more secure, staff cuts and reorganization of the USDA still have caused setbacks. APHIS is expected to lose 15% of employees – 1,180 people. Four hundred APHIS employees accepted the Administration’s deferred resignation offer. These included the leadership of many programs – including the previous Deputy Administrator, Mark Davidson. Higher up, no one has been appointed to the position of Deputy Secretary for Marketing and Regulatory Affairs.
In his report to the meeting, APHIS Acting Deputy Administrator for Plant Protection and Quarantine Matthew Rhoads noted that the Administration’s Farm Security Plan, which emphasizes efforts to combat bioterrorism, includes APHIS’ safeguarding role. However, abrupt and incomplete leadership changes hamper efforts to replace those who have left and set agency priorities. While I am cheered by the reported priority for preventing pest introductions, I fear that the focus might be quite narrow, leaving out threats to natural resources such as native forest trees.
Rhoads announced that after years of effort, the Asian longhorned beetle has been declared eradicated on 12.3 square miles of the Massachusetts quarantine zone.
Much of the presentation by Matthew Rhoads and later ones by other APHIS staff updated attendees on progress on technologies important in pest detection and control, and specific projects being carried out jointly by APHIS and NPB members (that is, state regulatory officials chosen to represent the state phytosanitary agencies). I consider the collaborative projects — begun in February 2023 – to be very important. Twenty years ago, relations between APHIS and its state counterparts were characterized by an “us vs. them” attitude.
I will summarize progress on the projects of greatest interest to those of us focused on non-native insects and disease pathogens threatening tree species. Rhodes mentioned improvements in the plant pathogen diagnostic certification program and development of improved molecular diagnostics for 45 insects and plant pathogens, including several Phytophthora species.
Joint APHIS-NPB teams have completed many risk analyses: 18 datasheets, 20 assessments, and four pathway analyses. As usual, insects – especially beetles – are the most numerous taxa detected. Many were surprised that the majority of new detections occurred in the south. When he was asked about this, Rhoads speculated that this reflected the region’s more hospitable climate and Florida’s surveillance efforts. I noted that ports in the southeast – e.g., Savannah and Charleston – are receiving higher import volumes; and that there have been problems with dunnage in the port of Houston.
Large container ship docked at Port of Savannah; photo by F.T. Campbell
Rhoads praised the federal-state strategic alliance’s project targetting illegal importation of plants purchased on-line. His example should concern us: importation of as many as 10,000 black pine seedlings to Georgia. The state stopped sale of these plants and APHIS’ investigatory unit began an investigation. This example illustrates the volume of plants that might be moving in this trade. Several states asked APHIS to offer more help in countering trafficking involving smaller numbers. All agree that no one has yet figured out an effective way to control this pathway.
A second example of successful coordination between APHIS and the states was said to be the decision to not regulate Phytophthora austrocedri, a pathogen detected in several nurseries in Oregon in 2024. Possible hosts in the Pacific Northwest include the already-depleted Port Orford cedar, and here; Juniperus californica, J. grandis, J. occidentalis, and J. maritima. Federal and state plant health officials, in coordination with the nursery industry trade association (AmericanHort), reached this decision after determining that the pathogen has probably been present in Oregon for many years and been spread to other states on the large volumes of host plants shipped. Now it will be up to states and non-governmental conservation organizations to try to detect whether this pathogen has established and devise management strategies.
New Information (as of December 2025): someone has posted on the web a written explanation of this decision by APHIS to the National Plant Board. [Visit cdn.ymaws.com, search for “Phytopthora austro”]. APHIS estimated that delimitation surveys in just one nursery would cost more than $9 million. Because the pathogen cannot be detected by visual symptoms, even tracking spread requires expensive destructive sampling of large numbers of plants. Meanwhile, thousands of possibly infected plants have been shipped from at least two Oregon nurseries in recent years. APHIS concluded that a Federal survey program for P. austrocedri would not contribute to ultimately controlling the spread or eradication of this pathogen. The agency recommended instead that natural resource agencies adopt a “protective-style approach”, focused on actively managing highest-value natural sites.
Are federal, state, and non-governmental managers of the many types of ecosystems inhabited by junipers and cypresses equipped to do this?
Ordinarily, the USFS Forest Health Protection program would be in a position to assist states which want to manage this pest (assuming its establishment). But considering the current uncertainty regarding USFS’ future, blog states cannot count on that help.
Sky Stevens (entomologist on the staff of USFS Forest Health Protection program) reported on the situation at the USFS. She noted that the Congressional appropriations bills continue funding for the agency’s research program and collaboration with non-federal entities managing forests. Still, the USFS lost 5,200 people through “voluntary” resignations and firings.
The program of greatest importance to us, Forest Health, was cut from 18 people to 8. Stevens replaced the long-time national entomologist. The comparable pathologist has retired. Stevens is struggling to make decisions regarding the pathology program, especially since diseases are inherently more difficult. While the USFS is doing lateral exchanges to fill high-need vacancies, FHP has not yet been asked what the program needs.
According to Stevens, in 2024 about 9 million acres were impacted by forest pests. The FHP program treated 1 million acres. As usual, the (European) spongy moth was the largest target based on acreage. Other non-native species targetted were emerald ash borer, goldspotted oak borer, sudden oak death, Asian longhorned beetle, hemlock woolly adelgid, and rapid ‘ōhi‘a death. See summaries of these pests’ impacts and status here.
Continuation of these projects in 2025 often became trapped in the new Administration’s funding freezes; opportune times for effective actions were often missed. On-going projects include several targetting emerald ash borer and its hosts in Oregon and black ash swamps of the Midwest and Northeast; managing sudden oak death in Oregon and California; and delimitation surveys for rapid ‘ōhi‘a death. The SOD program benefits from approximately $3 million earmarked by Congress (out of the total funding for the forest health program of $48 million).
Stevens noted that it is difficult to discuss the program’s future given the uncertainty. Program staff hope to continue issuing products that help people understand forest health in their region – not limited to federal lands.
I learned from the review of the following programs and technical tools that many were funded by the grant program under APHIS’ Plant Pest and Disease Management and Disaster Prevention program (Plant Protection Act Section 7721). Clearly, America’s efforts to prevent and respond to invasions by plant pests (including invasive plants) would be far less robust without this grant program.
boxwood (box tree) garden at Gunston Hall – an 18th Century plantation near Alexandria, Virginia (site of the 2026 NPB meeting); Photo by Roger 4336 via Wikipedia
Wendy Jin, APHIS PPQ Associate Deputy Administrator, urged states to use pest forecast models developed under the SAFARIS program. These models incorporate information on weather; pest biology, environmental needs and impact; hosts; land cover; and relevant human activities. Fifty pests have been evaluated so far, apparently including Asian longhorned beetle, spongy moth, spotted lanternfly, and boxtree moth. (All but the last are described briefly under the “invasive species” tab here.) The goal is to provide managers information about the insect’s life stage at specific times in specific localities so that they can time their surveillance and management actions. However, I am somewhat worried because the models use current and historical weather data – which might not be pertinent as the climate warms. Worse, the modelers lack sufficiently detailed data to develop models for Alaska, Hawai`i, Puerto Rico, or Guam.
Dr. Carrie Harmon (Deputy Director, National Plant Diagnostic Network) described the resources available for states use from two diagnostics tools. Both were developed under grants which are now expiring. Therefore updates and further development will depend on renewal of the grants. The National Plant Diagnostic Network (NPDN) provides accurate data and alerts about appearances of plant diseases. APHIS is said to be collaborating closely to ensure as much data as possible is shared. A separate body, the Diagnostic Assay Validation Network, is validating diagnostic assays.
A few years ago the NPB and APHIS formalized their new level of collaboration as the “Strategic Alliance, Strategic Initiative”. The Plant Board surveyed its members to gauge their feelings about several issues: 1) data-sharing issues that impede decision-making; 2) ways to strengthen coordination when dealing with on-line sales of plants or other vectors of plant pests (see the pine-Georgia example above); and 3) what structures and practices could make resolving these problems easier.
One of the resulting initiatives is an analysis of implementation of the Federal Noxious Weed program in the absence of a line-item appropriation. However, the President’s “Department of Government Efficiency” (DOGE) prompted resignations and firings, including this project’s APHIS liaison. Without a replacement, it is unclear how the analysis can proceed.
Another speaker, representing Bob Baca, Assistant Director of APHIS Plant Protection and Quarantine, warned state officials about new pressure to phase out use of methyl bromide (MB) as a phytosanitary tool. Use of ozone-depleting chemicals – including MB – has been regulated since 1988 under the Montreal Protocol. Americans use more MB for this purpose than any other country. Already manufacturers are ending its production. After mentioning substitutes under development, the speaker urged state departments of Agriculture to meet with growers and develop a nation-wide plan to weather this impending change. She noted that APHIS has no authority to require companies to produce substitutes.
The NPB leadership discussed turnover in the organization (several states are represented by officials new to their jobs); advocacy to APHIS for even better coordination and recognition of states’ need to act quickly; and efforts to expand its collaboration with other entities. A series of presentations tallied lessons learned during specific plant pest crises. These included the role of the public in pest detection; mobilizing initial responses to a new pest; and building higher-ups’ and legislators’ support for funding a “rapid response” capability before arrival of a new damaging pest.
In a separate blog I reviewed topics discussed that pertain particularly to Pacific island plant health issues.
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
stand of Miconia under albizia overstory on Big Island, Hawai`i; photo by F.T. Campbell
As I will describe in another blog, participants in the annual meeting of the National Plant Board link in Honolulu learned the basics about the uniqueness of agriculture and native species on remote Pacific islands. I want to complement this information by reminding you about other Hawaiian and Guamaian species at risk – although did not learn anything new.
As Martin and Andreozzi pointed out, the Pacific islands import nearly all their food and other consumables. Considerable interest in some quarters in Hawai`i to increase agricultural production. However, large swaths of land in the low-elevation area surrounding Pahoa on the Big Island is completely dominated by the albizia (Falcataria Molucca) [see photo above]. J.B. Friday says it is cost-prohibitive to remove these trees in order to restore agriculture in the area. Local people are concerned because in storms the trees fall onto houses and roads, causing considerable damage.
I saw numerous clumps of the notorious invasive plant Miconia calvescens. Dr. Friday told me that conservationists now focus on keeping this plant out of key areas, not trying to eradicate it completely.
area being restored by volunteers; photo by F.T. Campbell
Local people trying to restore disease-damaged forests by planting other native plants and hand-clearing invasive plants. Some of the ohia seedlings infected by Austropuccinia psidii.
ohia seedling with symptoms of ohia rust (Austropuccinia psdii); detected by J.B. Friday; photo by F.T. Campbell
Dr. Friday showed me many areas where ʻōhiʻa trees have been killed by rapid ʻōhiʻa death. Since this mortality occurred a decade or more ago, other plants have grown up. Pic In many if not most cases, this jungle includes dense growths of guava Latin the most widespread invasive tree on the islands (Potter). ‘Ōhi‘a trees continue to thrive in Hawai`i Volcanoes National Park – also on the Big Island – because the NPS makes considerable efforts to protect them from wounding by feral pigs. Demonstrates importance of fencing and mammal eradication in efforts to protect this tree species.
healthy ʻōhiʻa tree on cinder cone created by eruption of Kilauea Iki in 1959; photo by F.T. Campbell
I also saw healthy koa (Acacia koa) in the park, especially at sites along the road to the trail climbing Mauna Loa.
Regarding the wiliwili tree, I was told that it remains extremely scarce on Oahu.
wiliwili tree in flower; photo by Forrest Starr
I heard nothing about the status of naio – another shrub native to the Big Island – but on the dry western side of the island.
I rejoice that scientists are making progress in protecting and restoring Hawaii’s endemic bird species. Specifically, they are at the early stages of controlling mosquitoes that transmit fatal diseases. All 17 species of endemic honeycreepers that have persisted through the 250 years since Europeans first landed on the Islands are now listed as endangered or threatened under the federal Endangered Spp Act. The “Birds, not Mosquitoes” project has developed lab-reared male mosquitoes that, when they mate with wild female, the resulting eggs are sterile. (Male mosquitoes don’t bite, so increasing their number does not affect either animals or people.) Over time, the invasive mosquito population will be reduced, giving vulnerable native bird populations the chance to recover. Scientists began releasing these modified mosquitoes in remote forests on Maui and Kaua‘i in November 2023. In spring 2025, they began testing releases using drones. Use of drones instead of helicopters reduces the danger associated with flying close to complicated mountain rides in regions with variable weather. This project should be able to continue; the Senate Appropriations Committee report for FY26 allocates $5,250,000 for this project.
American Bird Conservancy is sponsoring a webinar about this program. It will be Wednesday, August 27, 2025 4:00 PM – 5:00 PM ET. Sign up for the webinar here
thicket of guava on the Big Island, Hawai`i; photo by F.T. Campbell
Finally, scientists are releasing a biocontrol agent targetting strawberry guava, Psidium cattleyanum, the most widespread invasive tree on the Islands (Potter et al. 2023). Distribution involves an interesting process. A stand of guava is cut down to stimulate rapid growth. The leaf-galling insect Tectococcus ovatus reproduces prolifically on the new foliage. Twigs bearing the eggs of these insects are collected and tied into small bundles. The bundles are then dropped from helicopters into the canopies of dense guava stands, where they establish and feed – damaging the unwanted host.
brown tree snake; photo via Wikimedia
Guam
Guam’s endemic birds have famously been extinguished by the non-native brown tree snake. Dr. Aaron Collins, State Director, Guam and Western Pacific, USDA APHIS Wildlife Services, informed participants at the National Plant Board meeting about the extensive efforts to suppress snake populations in military housing on the island, reduce damage to the electric grid, and prevent snakes from hitchhiking to other environments, especially Hawai`i and the U.S. mainland.
The program began more than 30 years ago, in 1993. The program now employs 80 FTEs and has a budget of $4 million per year. It was initiated because live and dead snakes had been found in shipments and planes that landed in Hawai`i and the U.S. mainland. Avoiding the snake’s establishment on Hawai`i is estimated to save $500 million per year. The program is a coordinated effort by USDA, U.S. Fish and Wildlife Service, and the Department of Defense. Probably this estimate helped advocates reverse a decision by the “Department of Government Efficiency” to defund the program.
The program enjoys some advantages over vertebrate eradication programs on the mainland. For example, since Guam has no native snakes, it can use poison, e.g., in mouse-baited traps that can be dropped from planes. A recent innovation is auto-resetting traps baited with mammals; they can electrocute numerous snakes per night.
SOURCE
Potter, K.M., C. Giardina, R.F. Hughes, S. Cordell, O. Kuegler, A. Koch, E. Yuen. 2023. How invaded are Hawaiian forests? Non‑native understory tree dominance signals potential canopy replacement. Lands. Ecol. https://doi.org/10.1007/s10980-023-01662-6
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
several Euwallaceae species; E. interjectus is 2nd from the top. Photo from Gomez et al. 2018; ZooKeys 768 19-68
In December 2024, California officials announced detection of a third species of invasive shothole borer beetle in the state. This invasion was found in Santa Cruz County in October 2024. The beetle has been identified as Euwallacea interjectus; the associated fungus is Fusarium floridanum. Like other non-native shothole borers in the same genus already known to be in California, Euwallacea interjectus is native to Southeast Asia.
So far, the infestation extends across at least 75 acres (CDFA proposal). It is affecting primarily box elders (Acer negundo). Other tree species have also been attacked: California sycamore (Platanus racemose), coast live oak (Quercus agrifolia), arroyo willow (Salix lasiolepis), red willow (Salix laevigata), and black cottonwood (Populus balsamifera ssp. trichocarpa). [See the CDFA risk assessment referred to below]. While it is too early to know precisely, E. interjectus is expected to pose a risk of tree dieback in urban, wildland and agricultural landscapes similar to that already caused by its relatives — the Polyphagous shot hole borer (Euwallacea fornicatus s.s. [PSHB]) and Kuroshio shot hole borer (Euwallaceakuroshio [(KSHB)].
The Santa Cruz County Department of Agriculture and University of California Cooperative Extension Service are coordinating with the California Department of Food and Agriculture (CDFA) to monitor and respond to the infestation. Research is being conducted by the University of California to evaluate the full range of potential tree species that may be affected by the beetle.
CDFA is seeking input on whether to designate Euwallacea interjectus as a category “B” pest. Under this category, response to the pest would be carried out by the counties at their own discretion, not by the state. You can advise CDFA’s on this decision until 17 February. Go here.
In its proposal, CDFA notes that several tree hosts of the beetle grow throughout California. The analysis gave a risk ranking of “High (3)” in four categories: climate/host interaction, host range, dispersal and reproduction, and ecosystem-level impacts. The economic risk rank is “Medium (2)” because it might attack only stressed trees – although CDFA concedes that drought stress is common in California. The overall determination is that the consequences of Euwallacea interjectus’ introduction to California is “High (14)”. Still, CDFA proposes to leave response to this introduction up to affected counties.
Santa Cruz County is outside the areas identified by a model developed by Lynch et al. (full citation below) as being at high risk of establishment of the Euwallacea-Fusarium complex, based on analysis of sites where Euwallacea fornicatus and E. kuroshio are already established. Nearby areas are ranked at high risk; these include drier areas in the San Francisco Bay region.
There are at least three four beetles in the Euwallacea fornicatus species complex. Several look almost identical to one another; the only reliable way to tell them apart is by looking at their DNA. However, E. interjectus is substantially larger than E. fornicatus and E. kuroshio, the two already-established shothole borers causing damage in southern California.
Various members of the Euwallacea fornicatus species complex have invaded countries around the world and other parts of the United States. While many of these introductions occurred decades ago – e.g., Hawai`i, Florida, possibly Israel, there appears to have been a spurt of introductions around or after 2000. The PSHB was first detected in California in 2003; the KSHB in 2013. As of 2022, disease caused by these two complexes had spread throughout Orange, San Diego, Los Angeles, Riverside, San Bernardino and Ventura counties. Outbreaks have been detected as far north as Santa Barbara /Santa Clarita. The KSHB had “jumped” to more distant locations in San Luis Obispo and Santa Clara counties. So far, the two later detections apparently do not represent established populations. In November 2023, the PSHB beetle–pathogen complex was confirmed killing hundreds of trees in riparian forests in San Jose, in the San Francisco Bay region. Two host trees – California sycamore and valley oaks – are important in the urban forest canopy of the region
NOTE: the invasive shot hole borers and their associated fungi attacking trees in California are completely unrelated to the laurel wilt complex killing trees in the Lauraceae family in eastern States. This complex involves an ambrosia beetle Xyleborus glabratus and associated fungus Harringtonia (formerly Raffaelea) lauricola.
Lynch, S.C., E. Reyes-Gonzalez, E.L. Bossard, K.S. Alarcon, N.L.R. Love, A.D. Hollander, B.E. Nobua-Behrmann & G.S. Gilbert. 2024. A phylogenetic epidemiology approach to predicting the establishment of multi-host plant pests Communications Biology
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at https://treeimprovement.tennessee.edu/
ʻŌhiʻa trees killed by ROD; photo by Richard Sniezko, USFS
Several Hawaiian tree species are at risk due to introduced forest pests. Two of the Islands’ most widespread species are among the at-risk taxa. Their continuing loss would expose watersheds on which human life and agriculture depend. Habitats for hundreds of other species – many endemic and already endangered – would lose their foundations. These trees also are of the greatest cultural importance to Native Hawaiians.
I am pleased to report that Hawaiian scientists and conservationists are trying to protect and restore them.
Other tree species enjoy less recognition … and efforts to protect them have struggled to obtain support.
1) koa (Acacia koa)
Koa is both a dominant canopy tree and the second-most abundant native tree species in Hawai`i in terms of areas covered. The species is endemic to the Hawaiian archipelago. Koa forests provide habitat for 30 of the islands’ remaining 35 native bird species, many of which are listed under the U.S. Endangered Species Act. Also dependent on koa forests are native plant and invertebrate species and the Islands’ only native terrestrial mammal, the Hawaiian hoary bat. Finally, koa forests protect watersheds, add nitrogen to degraded soils, and store carbon [Inman-Narahari et al.]
Koa forests once ranged from near sea level to above 7000 ft (2100 m) on both the wet and dry sides of all the large Hawaiian Islands. Conversion of forests to livestock grazing and row-crop agriculture has reduced koa’s range. Significant koa forests are now found on four islands – Hawai’i, Maui, O‘ahu, and Kauaʻi. More than 90% of the remaining koa forests occur on Hawai`i Island (the “Big Island) [Inman-Narahari et al.]
In addition to its fundamental environmental role, koa has immense cultural importance. Koa represents strength and the warrior spirit. The wood was used traditionally to make sea-going canoes. Now Koa is widely used for making musical instruments, especially guitars and ukuleles; furniture, surfboards, ornaments, and art [Inman-Narahari et al.]
Koa timber has the highest monetary value of any wood harvested on the Islands. However, supplies of commercial-quality trees are very limited (Dudley et al. 2020). Harvesting is entirely from old-growth forests on private land. [Inman-Narahari et al.]
Koa forests are under threat by a vascular wilt disease caused by Fusarium oxysporum f. sp. koae (FOXY). This disease can kill up to 90% of young trees and – sometimes — mature trees in native forests. The fungus is a soil-dwelling organism that spreads in soil and infects susceptible plants through the root system (Dudley et al. 2020).
Conservation and commercial considerations have converged to prompt efforts to breed koa resistant to FOXY. Conservationists hope to restore native forests on large areas where agriculture has declined. The forestry industry seeks to enhance supplies of the Islands’ most valuable wood. Finally, science indicated that a breeding program would probably be successful. Field trials in the 1990s demonstrated great differences in wilt-disease mortality among seed sources (the proportion of seedlings surviving inoculation ranged from 4% to 91.6%) [Sniezko 2003; Dudley et al. 2009].
In 2003, Dudley and Sniezko outlined a long-term strategy for exploring and utilizing genetic resistance in koa. Since then, a team of scientists and foresters has implemented different phases of the strategy and refined it further (Dudley et al. 2012, 2015, 2017; Sniezko et al. 2016]
First, scientists determined that the wilt disease is established on the four main islands. Having obtained more than 500 isolates of the pathogen from 386 trees sampled at 46 sites, scientists tested more than 700 koa families from 11 ecoregions for resistance against ten of the most highly virulent isolates (Dudley et al. 2020).
The Hawaiian Agricultural Research Center (HARC), supported by public and private partners, has converted the field-testing facilities on Hawai`i, Maui, and Oahu into seed orchards. The best-performing tree families are being grown to maturity to produce seeds for planting. It is essential that the seedlings be not just resistant to FOXY but also adapted to the ecological conditions of the specific site where they are to be planted [Dudley et al. 2020; Inman-Narahari et al. ] Locally adapted, wilt-resistant seed has been planted on Kauaʻi and Hawai`i. Preparations are being made to plant seed on Maui and O‘ahu also. Scientists are also exploring methods to scale up planting in both restoration and commercial forests [R. Hauff pers. comm.].
koa; photo by David Eickhoff via Flickr
Restoration of koa on the approximately half of lands in the species’ former range that are privately owned will require that the trees provide superior timber. Private landowners might also need financial incentives since the rotation time for a koa plantation is thought to be 30-80 years. [Inman-Narahari et al.]
Plantings on both private and public lands will need to be protected from grazing by feral ungulates and encroachment by competing plants. These management actions are intensive, expensive, and must be maintained for years.
Some additional challenges are scientific: uncertainties about appropriate seed zones, efficacy of silvicultural approaches to managing the disease, and whether koa can be managed for sustainable harvests. Human considerations are also important: Hawai`i lacks sufficient professional tree improvement or silvicultural personnel, a functioning seed distribution and banking network — and supporting resources. Finally, some segments of the public oppose ungulate control programs. Inman-Narahari et al.
Finally, scientists must monitor seed orchards and field plantings for any signs of maladaptation to climate change. (Dudley et al. 2020).
2) ʻŌhiʻa Metrosideros polymorpha)
ʻŌhiʻa lehua is the most widespread tree on the Islands. It dominates approximately 80% the biomass of Hawaii’s remaining native forest, in both wet and dry habitats. ʻŌhiʻa illustrates adaptive radiation and appears to be undergoing incipient speciation. The multitude of ecological niches and their isolation on the separate islands has resulted in five recognized species in the genus Metrosideros. Even the species found throughout the state, Metrosideros polymorpha, has eight recognized varieties (Luiz et al. (2023) (some authorities say there are more).
Loss of this iconic species could result in significant changes to the structure, composition, and potentially, the function, of forests on a landscape level. High elevation ‘ohi‘a forests protect watersheds across the state. ʻŌhiʻa forests shelter the Islands’ one native terrestrial mammal (Hawaiian hoary bat), 30 species of forest birds, and more than 500 endemic arthropod species. Many species in all these taxa are endangered or threatened (Luiz et al. 2023). The increased light penetrating interior forests following canopy dieback facilitates invasion by light-loving non-native plant species, of which Hawai`i has dozens. There is perhaps no other species in the United States that supports more endangered taxa or that plays such a geographical dominant ecological keystone role [Luiz et al. 2023]
For many Native Hawaiians, ‘ōhi‘a is a physical manifestation of multiple Hawaiian deities and the subject of many Hawaiian proverbs, chants, and stories; and foundational to the scared practice of many hula. The wood has numerous uses. Flowers, shoots, and aerial roots are used medicinally and for making lei. The importance of the biocultural link between ‘ōhi‘a and the people of Hawai`i is described by Loope and LaRosa (2008) and Luiz et al. (2023).
In 2010 scientists detected rapid mortality affecting ‘ōhi‘a on Hawai‘i Island. Scientists determined that the disease is caused by two recently-described pathogenic fungi, Ceratocystis lukuohia and Ceratocystis huliohia. The two diseases, Ceratocystis wilt and Ceratocystis canker of ʻōhiʻa, are jointly called “rapid ‘ōhi‘a death”, or ROD. The more virulent species, C. lukuohia, has since spread across Hawai`i Island and been detected on Kaua‘i. The less virulent C. huliohia is established on Hawai`i and Kaua‘i and in about a dozen trees on O‘ahu. One tree on Maui was infected; it was destroyed, and no new infection has been detected [M. Hughes pers. comm.] As of 2023, significant mortality has occurred on more than one third of the vulnerable forest on Hawai`i Island, although mortality is patchy.
[ʻŌhiʻa is also facing a separate disease called myrtle rust caused by the fungus Austropuccinia psidii; to date this rust has caused less virulent infections on ‘ōhi‘a.]
rust-killed ‘ōhi‘a in 2016; photo by J.B. Friday
Because of the ecological importance of ‘ōhi‘a and the rapid spread of these lethal diseases, research into possible resistance to the more virulent pathogen, C. lukiohia began fairly quickly, in 2016. Some ‘ōhi‘a survive in forests on the Big Island in the presence of ROD, raising hopes that some trees might possess natural resistance. Scientists are collecting germplasm from these lightly impacted stands near high-mortality stands (Luiz et al. 2023). Five seedlings representing four varieties of M. polymorpha that survived several years’ exposure to the disease are being used to produce rooted cuttings and seeds for further evaluation of these genotypes.
ʻŌhiʻa flowers
Encouraged by these developments, and recognizing the scope of additional work needed, in 2018 stakeholders created a collaborative partnership that includes state, federal, and non-profit agencies and entities, ʻŌhiʻa Disease Resistance Program (‘ODRP) (Luiz et al. 2023). The partnership seeks to provide baseline information on genetic resistance present in all Hawaiian taxa in the genus Metrosideros. It aims further to develop sources of ROD-resistant germplasm for restoration intended to serve several purposes: cultural plantings, landscaping, and ecological restoration. ‘ODRP is pursuing screenings of seedlings and rooted cuttings sampled from native Metrosideros throughout Hawai`i while trying to improve screening and growing methods. Progress will depend on expanding these efforts to include field trials; research into environmental and genetic drivers of susceptibility and resistance; developing remote sensing and molecular methods to rapidly detect ROD-resistant individuals; and support already ongoing Metrosideros conservation. If levels of resistance in wild populations prove to be insufficient, the program will also undertake breeding (Luiz et al. 2023).
To be successful, ‘ODRP must surmount several challenges (Luiz et al. 2022):
increase capacity to screen seedlings from several hundred plants per year to several thousand;
optimize artificial inoculation methodologies;
determine the effects of temperature and season on infection rates and disease progression;
find ways to speed up seedlings’ attaining sufficient size for testing;
develop improved ways to propagate ʻōhiʻa from seed and rooted cuttings;
establish sites for field testing of putatively resistant trees across a wide range of climatic and edaphic conditions;
establish seed orchard, preferably on several islands;
establish systems for seed collection from the wide variety of subspecies/varieties;
if breeding to enhance resistance is appropriate, it will be useful to develop high-throughput phenotyping of the seed orchard plantings.
Developing ROD-resistant ‘ōhi‘a is only one part of a holistic conservation program. Luiz et al. (2023) reiterate the importance of quarantines and education to curtail movement of infected material and countering activities that injure the trees. Fencing to protect these forests from grazing by feral animals can drastically reduce the amount of disease. Finally, scientists must overcome the factors there caused the almost complete lack of natural regeneration of ‘ōhi‘a in lower elevation forests. Most important are competition by invasive plants, predation by feral ungulates, and the presence of other diseases, e.g., Austropuccinia psidii.
Hawaii’s dryland forests are highly endangered: more than 90% of dry forests are already lost due to habitat destruction and the spread of invasive plant and animal species. Two tree species are the focus of species-specific programs aimed at restoring them to remaining dryland forests. However, support for both programs seems precarious and requires stable long-term funding; disease resistance programs often necessitate decades-long endeavors.
naio in bloom; photo by Forrest & Kim Starr via Creative Commons
1) naio (Myoporum sandwicense)
Naio grows on all of the main Hawaiian Islands at elevations ranging from sea level to 3000 m. While it occurs in the full range of forest types from dry to wet, naio is one of two tree species that dominate upland dry forests. The other species is mamane, Sophora chrysophylla. Naio is a key forage tree for two endangered honeycreepers, palila (Loxioides bailleui) and `akiapola`au (Hemignathus munroi). The tree is also an important host of many species of native yellow-face bees (Hylaeus spp). Finally, loss of a native tree species in priority watersheds might lead to invasions by non-native plants that consume more water or increase runoff.
The invasive non-native Myoporum thrips, Klambothrips myopori, was detected on Hawai‘i Island in December 2008 (L. Kaufman website). In 2018 the thrips was found also on Oahu (work plan). The Myoporum thrips feeds on and causes galls on plants’ terminal growth. This can eventually lead to death of the plant.
Aware of thrips-caused death of plants in the Myoporum genus in California, the Hawaii Department of Lands and Natural Resources Division of Forestry and Wildlife and the University of Hawai‘i began efforts to determine the insect’s distribution and infestation rates, as well as the overall health of naio populations on the Big Island. This initiative began in September 2010, nearly two years after the thrips’ detection. Scientists monitored nine protected natural habitats for four years. This monitoring program was supported by the USFS Forest Health Protection program. This program is described by Kaufman.
naio monitoring sites from L. Kaufman article
The monitoring program determined that by 2013, the thrips has spread across most of Hawi`i Island, on its own and aided by human movement of landscaping plants. More than 60% of trees being monitored had died. Infestation and dieback levels had both increased, especially at medium elevation sites. The authors feared that mortality at high elevations would increase in the future. They found no evidence that natural enemies are effective controlling naio thrips populations on Hawai`i Island.
Kaufman was skeptical that biological control would be effective. She suggested, instead, a breeding program, including hybridizing M. sandwicensis with non-Hawaiian Myoporum species that appear to be resistant to thrips. Kaufman also called for additional programs: active monitoring to prevent thrips from establishing on neighboring islands; and collection and storage of naio seeds.
Ten years later, in February 2024, DLNR Division of Forestry and Wildlife adopted a draft work plan for exploring possible resistance to the Myoporum thrips. Early steps include establishing a database to record data needed to track parent trees, associated propagules, and the results of tests. These data are crucial to keeping track of which trees show the most promise. Other actions will aim to hone methods and processes. Among practical questions to be answered are a) whether scientists can grow even-aged stands of naio seedlings; b) identifying the most efficient resistance screening techniques; and c) whether K. myopori thrips are naturally present in sufficient numbers to be used in tests, or – alternatively – whether they must be augmented. [Plan]
Meanwhile, scientists have begun collecting seed from unaffected or lightly affected naio in hotspots where mortality is high. They have focused on the dry and mesic forests of the western side of Hawai`i (“Big”) Island, where the largest number of naio populations still occur and are at high risk. Unfortunately, these “lingering” trees remain vulnerable to other threats, such as browsing by feral ungulates, competition with invasive plants, drought, and reduced fecundity & regeneration.
Hawai`i DLNR has secured initial funding from the Department of Defense’s REPI program to begin a pest resistance project and is seeking a partnership with University of Hawai`i to carry out tests “challenging” different naio families’ resistance to the thrips [R. Hauff pers. comm.]
wiliwili; photo by Forrest & Kim Starr
2) wiliwili (Erythrina sandwicensis)
Efforts to protect the wiliwili have focused on biological control. The introduced Erythrina gall wasp, Quadrastichus erythrinae (EGW) was detected on the islands in 2005. It immediately caused considerable damage to the native tree and cultivated nonnative coral trees.
A parasitic wasp, Eurytoma erythrinae, was approved for release in November 2008 – only 3 ½ years after EGW was detected on O‘ahu. The parasitic wasp quickly suppressed the gall wasp’s impacts to both wiliwili trees and non-native Erythrina. By 2024, managers are once again planting the tree in restoration projects.
However, both the gall wasp and a second insect pest – a bruchid, Specularius impressithorax – can cause loss of more than 75% of the seed crop. This damage means that the tree cannot regenerate. By 2019, Hawaiian authorities began seeking permission to release a second biocontrol gent, Aprostocitus nites.Unfortunately, the Hawai’i Department of Agriculture still has not approved the release permit despite five years having passed. Once they have this approval, the scientists will then need to ask USDA Animal and Plant Health Inspection Service (APHIS) for its approval [R. Hauff, pers. comm.]
SOURCES
www.RapidOhiaDeath.org
Dudley, N., R. James, R. Sniezko, P. Cannon, A. Yeh, T. Jones, & Michael Kaufmann. 2009? Operational Disease Screening Program for Resistance to Wilt in Acacia koa in Hawai`i. Hawai`i Forestry Association Newsletter August 29 2009
Dudley, N., T. Jones, K. Gerber, A.L. Ross-Davis, R.A. Sniezko, P. Cannon & J. Dobbs. 2020. Establishment of a Genetically Diverse, Disease-Resistant Acacia koa Seed Orchard in Kokee, Kauai: Early Growth, Form, & Survival. Forests 2020, 11, 1276; doi:10.3390/f11121276 www.mdpi.com/journal/forests
Friday, J. B., L. Keith, and F. Hughes. 2015. Rapid ʻŌhiʻa Death (Ceratocystis Wilt of ʻŌhiʻa). PD-107, College of Tropical Agriculture and Human Resources, University of Hawai‘i, Honolulu, HI. URL: https://www.ctahr.HI.edu/oc/freepubs/pdf/PD-107.pdf Accessed April 3, 2018.
Friday, J.B. 2018. Rapid ??hi?a Death Symposium -West Hawai`i (“West Side Symposium”) March 3rd 2018, https://vimeo.com/258704469 Accessed April 4, 2018 (see also full video archive at https://vimeo.com/user10051674)
Inman-Narahari, F., R. Hauff, S.S. Mann, I. Sprecher, & L. Hadway. Koa Action Plan: Management & research priorities for Acacia koa forestry in Hawai`i. State of Hawai`i Department of Land & Natural Resources Division of Forestry & Wildlife no date
Kaufman, L.V, J. Yalemar, M.G. Wright. In press. Classical biological control of the erythrina gall wasp, Quadrastichus erythrinae, in Hawaii: Conserving an endangered habitat. Biological Control. Vol. 142, March 2020
Loope, L. and A.M. LaRosa. 2008. ‘Ohi’a Rust (Eucalyptus Rust) (Puccinia psidii Winter) Risk Assessment for Hawai‘i.
Luiz, B.C. 2017. Understanding Ceratocystis. sp A: Growth, morphology, and host resistance. MS thesis, University of Hawai‘i at Hilo.
Luiz, B.C., C.P. Giardina, L.M. Keith, D.F. Jacobs, R.A. Sniezko, M.A. Hughes, J.B. Friday, P. Cannon, R. Hauff, K. Francisco, M.M. Chau, N. Dudley, A. Yeh, G. Asner, R.E. Martin, R. Perroy, B.J. Tucker, A. Evangelista, V. Fernandez, C. Martins-Keli’iho.omalu, K. Santos, R. Ohara. 2023. A framework for establishlishing a rapid ‘Ohi‘a death resistance program New Forests 54, 637–660. https://doi.org/10.1007/s11056-021-09896-5
Sniezko, R.A., N. Dudley, T. Jones, & P. Cannon. 2016. Koa wilt resistance & koa genetics – key to successful restoration & reforestation of koa (Acacia koa). Acacia koa in Hawai‘i: Facing the Future. Proceedings of the 2016 Symposium, Hilo, HI: www.TropHTIRC.org , www.ctahr.HI.edu/forestry
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at https://treeimprovement.tennessee.edu/
Oregon ash dominate wetlands of Ankeny NWR; photo by Wyatt Williams, Oregon Department of Forestry
One of these insects is the emerald ash borer (EAB). We easterners have “been there & done that”. However, programs aimed at conserving wetlands and riparian areas of the Western states – and the associated species — are at least as vulnerable to loss of ash. Worse, other tree taxa, specifically oaks, and the open woodlands they inhabit — are also under threat. The ecological tragedies continue to affect ever more forests.
|Emerald Ash Borer in Oregon and British Columbia
The emerald ash borer (EAB; Agrilus planipennis) was detected in Oregon in June 2022. Officials had been expecting an introduction and had begun preparations. Unsurprisingly, the infestation is more widespread than known at first: detections in two new locations, fairly close to the original in Forest Grove, mean the infested area now occupies three neighboring counties — Washington, Yamhill, and Marion counties.
Oregon officials are trying to slow spread of EAB by removing infested trees. Surveys in Washington County had identified 190 infested ash trees; 80 were removed in April 2024. They treated healthy ash trees in Washington County with injections of the systemic insecticide emamectin benzoate. The effort was already a daunting task: the survey had disclosed 6,500 ash trees in the vicinity. The city of Portland – only 25 miles away – has 94,000 ash trees (Profita 2024).
In May, 2024 EAB was detected in the city of Vancouver in British Columbia. This detection in the sixth Canadian province adds to the threat to the ecosystems of the region. The Canadian Food Inspection Agency (CFIA) now regulates the movement of all ash material such as logs, branches, and woodchips, and all species of firewood, from the affected sites.
The CFIA is also conducting surveillance activities to determine where EAB might be present, and is collaborating with the City of Vancouver, the Vancouver Board of Parks and Recreation, the Province of British Columbia, and other stakeholders to respond to the detections and slow the spread of this pest.
Importance of Oregon ash (Fraxinus latifolia)
The Oregon ash is the only ash species native to the Pacific Northwest. Its range stretches from southern British Columbia to so California, where it has hybridized with velvet ash (F. velutina). It is highly susceptible to EAB attack; there is a high probability that Oregon ash could be rendered functionally extinct (Maze, Bond and Mattsson 2024). This vulnerability prompted the International Union for Conservation of Nature (IUCN) to classify Oregon ash as “near threatened” as long ago as 2017 (Melton et al. 2024).
Oregon ash typically grows in moist, bottomland habitats. There it is a late-successional climax species. In Oregon’s Willamette Valley and Washington’s Puget Trough, the tree improves streams’ water quality by providing shade, bank stabilization, and filtration of pollutants and excess nutrients. Maintaining these ecological services is particularly important because these streams are crucial to salmonids (salmon and trout) and other native aquatic species (Maze, Bond and Mattsson 2024).
So it is not surprising that one component of Oregonians’ pre-detection preparations was an analysis of the likely impact of widespread ash mortality on populations of salmon, trout, and other aquatic species. I summarize the key findings of Maze, Bond and Mattsson here.
According to this study, salmonids and other cold-water aquatic species suffer population declines and health effects when stream water temperatures are too warm. A critical factor in maintaining stream temperatures is shade – usually created by trees. In the Pacific Northwest many streams’ temperatures already exceed levels needed to protect sensitive aquatic species. A key driver of increased stream temperatures – at least in the Willamette Basin – is clearing of forests to allow agriculture.
Decreasing streams’ temperatures is not only a good thing to do; it is legally required by the Endangered Species Act because several salmon and steelhead trout species are listed. In one response, the Oregon Department of Environmental Quality recommends restoration and protection of riparian vegetation as the primary methods for increasing stream shading and mitigating increased stream temperatures in the lower Willamette Basin.
The forests shading many low-elevation forested wetlands and tributaries of the Willamette and lower Columbia rivers are often composed exclusively of Oregon ash. Loss of these trees’ shade will affect not just the immediate streams but also increase the temperature of mainstem waterways downstream.
Oregon ash – EAB detection site; photo by Wyatt Williams, Oregon Department of Forestry
Replacements for Oregon Ash?
The magnitude of the ecological impacts of ash mortality in the many forested wetlands in the Willamette Valley will largely be determined by what plant associations establish after the ash die. Oregon ash is uniquely able to tolerate soils inundated for extended periods. No native tree species can fill the void when the ash die. Oregon white oak (Quercus garryana), black cottonwood (Populus trichocarpa), and the alders (Alnus rubra and A. rhombifolia), are shade intolerant and unlikely to persist in later seral stages in some settings.
If non-native species fill the gaps, they will provide inferior levels of ecosystem services – I would think particularly regarding wildlife habitat and invertebrate forage. Maze, Bond and Mattsson expect loss of ash to trigger significant physical and chemical changes. These will directly impact water quality and alter native plant and animal communities’ composition and successional trajectories.
The authors cite expectations of scientists studying loss of black ash (F. nigra) from upper Midwestern wetlands. There, research indicates loss of ash from these systems is likely to result in higher water tables and a conversion from forested to graminoid- or shrub-dominated systems. Significant changes follow: to food webs, to habitat structure, and, potentially, to nitrogen cycling.
Maze, Bond and Mattsson expect similar impacts in Willamette Valley wetlands and floodplains, especially those with the longest inundation periods and highest water tables. That is, there will probably be a broad disruption of successional dynamics and, at many sites, a conversion to open, shrub-dominated systems or to wetlands invaded by exotic reed canary grass (Phalaris arundinacea), with occasional sedge-dominated (Carex obnupta) wetlands. They think this change is especially likely under canopies composed of Oregon white oak (see below). The authors admit some uncertainty regarding the trajectories of succession because 90 years of water-control projects has almost eliminated the possibility of high-intensity floods.
Steelhead trout
Oregon Ash and Salmonids
Maze, Bond and Mattsson point out that all salmonids that spawn in the Willamette basin and the nearly 250,000 square mile extent of the Columbia basin upstream of Portland pass through the two wooded waterways in the Portland area that they studied. Applying a model to simulate disappearance of ash from these forests, the authors found that the reduced shade would raise the “solar load” on one waterway, which is wide and slow-moving, by 1.8%. On the second, much narrower, creek (mean channel width of 7 m), solar load was increased by of 23.7%.
Maze, Bond and Mattsson argue that even small changes can be important. Both waterbodies already regularly exceed Oregon’s target water temperature throughout the summer. Any increase in solar loading and water temperatures will have implications for the fish – and for entities seeking to comply with Endangered Species Act requirements. These include federal, state, and local governments, as well as private persons.
The Willamette and lower Columbia Rivers, and their tributaries, traverse a range of elevations. Ash trees comprise a larger proportion of the trees in the low elevation riparian and wetland forests. Consequently, Maze, Bond and Mattsson expect that EAB-induced loss of Oregon ash will have significant impacts on these rivers’ water quality and aquatic habitats. The higher water temperatures will affect aquatic organisms at multiple trophic levels.
They conclude that the EAB invasion West of the Cascade Mountain range constitutes an example of the worst-case forest pest scenario: the loss of a dominant and largely functionally irreplaceable tree species that provides critical habitat for both ESA-listed and other species, along with degradation of ecosystem services that protect water quality.
Breeding Oregon Ash … Challenges to be Overcome
According to Melton et al. (2024), Oregon ash does not begin to reproduce until it is 30 years old. Such an extended reproductive cycle could complicate breeding efforts unless scientists are able to accelerate flowering or use grafting techniques to speed up reproduction – as suggested by Richard Sniezko, USFS expert on tree breeding.
Melton et al. (2024) note that the IUCN has recently highlighted the importance of maintaining a species’ genetic variation in order to maintain its evolutionary potential. Consequently, they examined genetic variation in Oregon ash in order to identify the species’ ability to adjust to both the EAB threat and climate change. The authors sequenced the genomes of 1,083 individual ash trees from 61 populations. These spanned the species’ range from Vancouver Island to southern California. The genetic analysis detected four genetic clusters:
British Columbia;
Washington to central Oregon – including the Columbia River and its principal tributaries;
Southwest Oregon and Northwest California — the Klamath-Siskiyou ecoregion; and
all other California populations.
Connectivity between populations (that is, the potential corridors of movement for pollen and seeds and hence, genetic flow) was greatest in the riparian areas of the Columbia River and its tributaries in the center to the species’ range. Despite this evidence of connectivity, nucleotide diversity and effective population size were low across all populations. This suggests that the patchy distribution of Oregon ash populations might reduce its long-term evolutionary potential. As average temperatures rise, the regional populations will become more distinct genetically. The species’ ability to adjust to future climate projections is most constrained in populations on Vancouver Island and in smaller river valleys at the eastern and western edges of the range. Populations in southern California might be “pre-adapted” to warmer temperatures.
The resulting lower effective population size might exacerbate risks associated with EAB. The authors warned that although seeds from more than 350 maternal parent trees have been preserved since 2019, these collections do not cover the full genomic variation across Oregon ash’s range. Some genomic variation that represents adaptive variation critical to the species’ long-term evolution might be missing. They advocate using the genetic data from their study to identify regions where additional collections of germplasm are needed for both progeny trials and for long-term conservation.
Oregon white oak with symptoms of Mediterranean oak borer infestation; photo by Christine Buhl, Oregon Department of Forestry
Oregon White Oak (Quercus garryana) and the Mediterranean Oak Borer
The U.S. Department of Interior has been working with regional partners for 10 years to protect oak and prairie habitat for five ESA-listed species, two candidate species, and numerous other plant and animal species of concern. In August 2025 the Department announced creation of the Willamette Valley Conservation Area. It becomes part of the Willamette Valley National Wildlife Refuge Complex. These units are managed predominantly to maintain winter habitat for dusky geese (a separate population of Canada geese). Other units in the Complex are William L. Finley National Wildlife Refuge, Ankeny National Wildlife Refuge, and Baskett Slough National Wildlife Refuge.
These goals too face threats from non-native forest pests. First, the forested swamps of Ankeny NWR are composed nearly 100% of ash.
Second, Oregon white oak now confronts its own non-native pest – the Mediterranean oak borer (Xyleborus monographus). This Eurasian ambrosia beetle has been introduced to the northern end of the Willamette Valley (near Troutville, Oregon). It is likely that infestations are more widespread. Authorities are surveying areas near Salem. A separate introduction has become established in California, north of San Francisco Bay plus in Sacramento County in the Central Valley. Oregon white oak is vulnerable to at least one of the fungi vectored by this borer – Raffaelea montety. https://www.dontmovefirewood.org/pest_pathogen/mediterranean-oak-borer/
SOURCES
Maze, D., J. Bond and M. Mattsson. 2024. Modelling impacts to water quality in salmonid-bearing waterways following the introduction of emerald ash borer in the Pacific Northwest, USA. Biol Invasions (2024) 26:2691–2705 https://doi.org/10.1007/s10530-024-03340-3
Melton, A.E., T.M. Faske, R.A. Sniezko, T. Thibault, W. Williams, T. Parchman, and J.A. Hamilton. 2024. Genomics-driven monitoring of Fraxinus latifolia (Oregon Ash) for conservation and emerald ash borer resistance breeding. https://link.springer.com/article/10.1007/s10530-024-03340-3
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at https://treeimprovement.tennessee.edu/
tanoak killed by P. ramorum; photo by F.T. Campbell
I am belatedly catching up on the situation with regard to Phytophthora ramorum – sudden oak death – in the US and other countries.
For a general factsheet on this plant disease, see profile here. Here, I’m summarizing more detailed information contained in the February, May, and August 2024 newsletters of the California Oak Mortality Task Force (COMTF) (Newsletters for earlier months are posted here.)
To obtain the most recent information, you can attend the Fall 2024 virtual meeting of the Task Force on Tuesday, October 29, 2024, from 1 pm to 3 pm PDT. Speakers will focus on the status of P. ramorum in California and Oregon wildlands.
On the next day, Wednesday, October 30, the Phytophthoras in Native Habitats Work Group will discuss “Threats to California Native Plants” including from viruses and excessive heat, along with other concerns.
Participation is free, but registration is required. Complete agendas and more information will be available soon here. Sessions will be recorded and posted to the same site. Questions? Contact Janice Alexander.
More in-depth information à Matteo Garbelotto’s UC Berkeley class, “Ecology and Impacts of Emergent Forest Diseases in California,” is now available free and online. Recommended reading, lecture recordings, slides, even essay topic suggestions are posted. Subjects covered include several high impact forest diseases, molecular diagnostics, disease control, and prevention.
I note that the recent detections of new outbreaks in forests and nurseries support the importance of weather in promoting or hindering establishment and spread of Phytophthora ramorum.
Phytophthora ramorum in North American Forests
In Oregon, P. ramorum continued to spread in 2023 and the first half of 2024.
These outbreaks were detected through extensive surveillance. Aerial monitoring (in cooperation with the USDA Forest Service) and high-resolution imagery covered more than half a million acres in Curry County — the region between the California border and the Coos County line. Ground surveys covered 860 acres. Sampling included 518 trees; 117 tested were positive for the fungus. Stream baits were deployed to 63 sites; 26 tested positive at least once (COMTF newsletter, February 2024; includes maps).
By summer 2024, 23 new P. ramorum infestations had been detected at or beyond the Generally Infested Area (GIA; the area where the pathogen is most commonly found) since 2021. Some of these involve one of the newly detected clonal lineages. Oregon officials are expecting to expand the state’s quarantine area to 901 square miles – 45% of Curry County. The designated GIA would also be enlarged to 178 square miles(COMTF newsletter, August 2024; contains maps).
Oregon continues trying to treat high-priority infestations. In 2023, the state treated 165 acres infested by one of the newly detected clonal lineages, NA2, in the Humbug Mountain area and 347 acres in the Port Orford infestation. Since 2001, Oregon’s Department of Forestry has completed eradication treatments on more than 9,000 acres at an estimated cost of over $37 million. Federal lands comprised 28% of treated acres; the remainder were private and state lands. Still, more than 1,000 high-priority acres have not been treated because neither state nor federal agencies could provide sufficient funds (COMTF newsletter, February 2024).
The stream baiting program in 64 stream drainages has – so far – detected six positive streams. Ground surveys are planned for the new positive drainages along the north bank of the Rogue River and a stream that drains into the Elk River east of Port Orford (COMTF newsletter, August 2024).
In California, recent wet winters have prompted several new detections. The first was in Del Norte County near previously detected sites. The UC Berkeley-coordinated “SOD Blitz” plans intensive surveys in this region in coming months (COMTF newsletter May 2024; contains map).
Somewhat later, new infestations were detected farther south, in Humboldt Redwoods State Park. The new sites were outside the formerly detected sites, on the north side of the creek and up to the top of the ridge (COMTF newsletter, August 2024).
Scientists have realized another concern: several other pathogens cause symptoms on bay laurel, tanoak, and madrone that are almost indistinguishable from SOD. This development will complicate monitoring (COMTF newsletter for August 2024; see below for more details).
Meanwhile, scientists determined that sites where the P. ramorum epidemic is driven by higher bay laurel (Umbellularia californica) densities sustained a higher genotypic diversity of P. ramorum. While tanoak (Notholithocarpus densiflorus) doesn’t contribute much to infection of true oaks (Quercus spp.) it can infect bay laurel, thus perpetuating the infection. Infected oaks and tanoaks maintain host-specific pathogen genotypes (Kozanitas et al. 2024)
The USDA Forest Service program that monitors streams in the East to detect P. ramorum placed baits in 63 streams in 10 eastern states: Alabama, Florida, Georgia, Illinois, Maryland, Mississippi, North Carolina, Pennsylvania, South Carolina, and Texas. In 2023, positive findings for P. ramorum were detected from two streams in Alabama, and one each in Mississippi and North Carolina. All sites are associated with nurseries that had previously tested positive for P. ramorum. Over the last five years – since 2019 – eight streams in four states have tested positive at least once: five in Alabama, and one each in Mississippi, North Carolina, and South Carolina. The detection in South Carolina is new. Vegetation in the watershed has been sampled multiple times; all samples collected so far — plant, soil, and run-off water – have been negative. The pathogen belongs to the NA1 lineage – the one established in forests in West Coast states. [COMTF newsletter February 2024]
from D.J. Haller & M.C. Wimberly. 2020
Situation in Europe
The February 2024, the COMTF newsletter summarized the situation in Great Britain. In England, aerial surveillance covered more than 31,000 ha of larch (Larix kaempferi)plantations. Follow-up investigations detected considerably fewer infested sites than the approximately 200 detected in 2022. Most remain in the southwest and northwest of the country. Weather conditions in 2023 were less conducive for sporulation in 2021 and 2022, which seemed to lead to a reduced level of disease in 2022 and 2023.
In Scotland, widespread aerial and ground surveillance detected a number of sites similar to those found since 2018. Scottish authorities note that where positive findings are not quickly followed by tree removal, localized spread occurred.
In Wales, four helicopter surveillance flights identified around 150 sites deserving further investigation. About 60 of these sites held infected trees, mainly larch, but some noble fir (Abies procera). The COMTF newsletter contains a map showing infested locations. This year’s infection level might be less than in previous years, but this might reflect the fact that the infections are in smaller forest blocks. However, the wet and mild weather in autumn/winter 2023 provided optimal conditions for sporulation, so the scientist expected higher infection rates in 2024. The Welsh Government is working on a new strategy for managing P. ramorum.
In Northern Ireland, P. ramorum was described as still active and spreading. Only two surveys were flown. They identified 49 locations for follow-up, many in forests where the pathogen had been found previously. At two locations, follow-up inspections and sampling of larch confirmed infection by a different pathogen, Phytophthora pseudosyringae. So in 2024, larch samples will be tested for both P. ramorum and P. pseudosyringae.
Other Phytopthoras in Europe
English scientists are trying to determine how damaging P. pseudosyringae is on larch. Infections have been observed at several locations in the north of England, as well as in Northern Ireland (COMTF newsletter February 2024).
Mullet et al. (2024) report that P. pseudosyringae is a self-fertile pathogen of woody plants, especially tree species in the genera Fagus, Notholithocarpus, Nothofagus and Quercus. It is found across Europe and in parts of North America and Chile. Genetic studies show that the North American population originated from Europe. P. pseudosyringae can infect roots; the stem collar region; bark; twigs and stems; as well as leaves. They report it is causing particular damage in Great Britain and western North America. Mullet et al. call for investigation of differences in life history traits between the two main population clusters, including their virulence and host ranges.
Nothofagus obliqua; photo by Line1 via Wikimedia
Chile (COMTF newsletter May 2024)
Concerned about decades of mortality of Nothofagus trees in native forests in Chile, González et al. 2024 sought to understand which other native plants might be reservoirs of inoculum of the pathogen Phytophthora pseudosyringae — which is a documented causal agent of partial defoliation and bleeding cankers on two native tree species,Nothofagus obliqua and N. alpina. P. pseudosyringae can sporulate on lesions on Cryptocarya alba, Nothofagus dombeyi and N. obliqua leaves. On Sophora macrocarpa, sporulation occurs on both asymptomatic tissues and on lesions. S. macrocarpa is a common understory species in Nothofagus forests, so it might be an inoculum reservoir for epidemic events in them.
Look-alikes on California Bay Laurel (COMTF newsletter May 2024)
Similar symptoms from a wide variety of pathogenic organisms were detected on bay laurels after last year’s wet winter. Among the pathogens — the list is not exhaustive — includes P. cinnamomi, Neofusicoccum nonquaesitum, Ganoderma brownie, P. pseudosyringae, P. nemorosa, Botryosphaeria dothidea, Armillaria gallica, Diplodia corticola, and others.
Foliar symptoms tend to look identical on bay laurel leaves. Two foliar pathogens cause particular concern. The first is an “anthracnose” disease of bay laurel caused by a species of Kabatiella. Although known to be present for ~80 years, this organism did not seem to cause problems until 2023. In multiple locations around the San Francisco Bay area, it has caused extensive browning defoliation of bay laurel crowns. Whether the trees will die is uncertain.
The second focus is on a recently named species, Calonectria californiensis. This organism produces P. ramorum-like similar symptoms on a wide variety of native plants, including bay laurel, tanoak, salal, mock-orange, Oregon-grape, and rhododendron. On most of these plants this fungus causes black spots that can grow to kill entire leaves, but apparently C. californiensis is not a pathogen of woody plant parts. Initial symptoms of infection on bay laurel appear identical to those caused by the SOD pathogen (Phytopthora ramorum). C. californiensis does not appear (yet) to lead to lasting debilitating disease or tree mortality.
Nurseries and Managed Landscapes
In administering APHIS’ cooperative program aimed at minimizing spread of P. ramorum via interstate trade in plants, California’s Department of Agriculture (CDFA) relies – at least in part – on funds from USDA. CDFA received $1,308,771 from APHIS in 2023. More than 300 establishments in California are regulated under the program. They submitted ~ 7,400 P. ramorum regulatory samples to the CDFA in 2023. Seventy-eight of the samples were positive (COMTF newsletter February 2024).
At the end of 2023, seven California nurseries that had tested positive for the presence of P. ramorum were operating under the APHIS regulation governing positive nurseries. This was an increase over previous years; zero in 2022, three in 2021 (COMTF newsletter February 2024 Table 4). During 2024 five nurseries were confirmed as positive. Three of these had tested positive in previous years. Two retail nurseries were newly positive; one of these was apparently infected when it brought in plants from another nursery (COMTF newsletter August 2024). I wonder whether the very wet winters California has experienced lately have enhanced the pathogen’s ability to grow – and be detected.
In Oregon, in 2023 the Department of Agriculture regulated five interstate shippers under federal compliance agreements and a sixth intrastate shipper regulated under state requirements (COMTF newsletter February 2024). Spring compliance surveys tested 1,228 foliar samples; ten were positive. After this nursery incinerated all nearby plants, none of the 1,664 foliar samples tested in the fall was positive.
In 2023, the Washington State Department of Agriculture processed more than 300 plant, soil, and water samples; all were negative. Washington also inspected five of the nine nurseries that had ‘opted-out’ of the Federal program so they can no longer ship interstate. Host material appeared free of symptoms so no samples were collected (COMTF newsletter February 2024).
Washington nurseries and regulators frequently encounter the problem of infected plants being shipped into the state from outside. (P. ramorum has been found in 33 Washington nurseries since 2003.) During 2023, the Washington State Department of Agriculture conducted three trace-forward investigations. Fortunately no infestations were detected (COMTF newsletter February 2024). In March 2024, Washington faced another trace-forward involving plants sold to homeowners (COMTF newsletter May 2024). Thirteen tissue samples and two soil samples all tested negative (COMTF newsletter August 2024)
Finally, Washington conducted stream baiting. In 2023, none of the 66 samples was positive (COMTF newsletter February 2024)
Infested Plants
Most of the plant species on which P. ramorum was detected during these years are the usual ones: Rhododendron, Viburnum, Pieris, Arbutus, Prunus, Camellia, Loropetalum. I think the several Cornus species might be somewhat unusual. Disease was confirmed on a new Cornus species, C. capitata (evergreen dogwood). One taxon — Arbutus x ‘Marina’ — is not yet listed by APHIS as a host because Koch’s postulates have not been completed (COMTF newsletters for February 2024 and August 2024).
Research (summarized in the February 2024 newsletter)
Two studies found evidence of seasonal and weather factors influenced establishment of P. ramorum. One study found a clear seasonal pattern of pathogen incidence in the western US, plus a link to the El Niño-Southern Oscillation (ENSO) (Xuechung et al. 2024. The second study looked at a Japanese larch plantation in Scotland (Dun et al. 2024).
In both Scotland (above) and France (Beltran et al. 2024 2024), scientists demonstrated that prompt action helps to suppress P. ramorum establishment.
APHIS Updates its Regulations
In March 2024, APHIS revised the P. ramorum “Domestic Regulatory Program Manual.” The agency said it updated figures and definitions, clarified operational steps, and revised the Retail Nursery Dealer Protocol (COMTF newsletter for May 2024).
Funding
In Fiscal Year 2024, under the Plant Protection Act Section 7721 program, APHIS funded $1 million worth of projects focused on P. ramorum and related species. This was out of a total $62 million in funds dispersed for pest survey, research, mitigation, and outreach programs. This money funded nursery surveys in 11 states. Also, it paid for a project to evaluate the threat of the NA2 & EU2 lineages to nurseries and forests (COMTF newsletter May 2024).
SOURCES
Beltran, A.; Laubray, S.; Ioos, R.; Husson, C.; Marçais, B. 2024. Low persistence of Phytophthora ramorum in western France after implementation of eradication measures. Annals of Forest Science. 81: 7. https://doi.org/10.1186/s13595-024-01222-1
Dun, H.F.; MacKay, J.J. & Green, S. 2024. Expansion of natural infection of Japanese larch by Phytophthora ramorum shows trends associated with seasonality & climate. Plant Pathology. 73(2): 419-430).
González, M.P.; Mizubuti, E.S.G.; Gonzalez, G.; Sanfuentes, E. 2024. Uncovering the hidden hosts: Identifying inoculum reservoirs for Phytophthora pseudosyringae in Nothofagus forests in Chile. Plant Pathology. 73(4): 937-947. https://doi.org/10.1111/ppa.13855. (Summarized in COMTF newsletter February 2024.)
Kozanitas, M.; Knaus, B.J.; Tabima, J.F.; Grünwald, N.J.; Garbelotto, M. 2024. Climatic variability, spatial heterogeneity & the presence of multiple hosts drive the population structure of the pathogen P ram & the epidemiology of Sudden Oak Death. Ecogeography. https://doi.org/10.1111/ecog.07012. (Summarized in COMTF newsletter May 2024.)
Mullet, M.S.; Harris, A.R.; Scanu, B. [and others]. 2024. Phylogeography, origin & population structure of the self-fertile emerging plant pathogen Phytophthora pseudosyringae. Molecular Plant Pathology. https://doi.org/10.1111/mpp.13450. (Summarized in COMTF newsletter for May 2024.)
Xuechung, K.; Wei, C.; Siliang, L.; Tiejun, W.; Le, Y. & Singh, R. 2024. Spatiotemporal distribution of sudden oak death in the US & Europe. Agricultural & Forest Meteorology. 346: 109891)
feral hogs in state wildlife area, Florida; photo by Craig Oneal via Flickr
Most invasive species detection and control programs suffer from inadequate funding. Feral hogs (Sus scrofa) are the exception. True, feral hogs are widely considered among the most damaging of invasive species. They are conspicuous. And they cause damage to agricultural crops – thus energizing a politically powerful constituency. (The extent of that damage is open to question; see my discussion below.) Can we learn from the political success of this program to build support for countering other invasive species?
[Several forest pests are also listed as among the “100 worst” invasive species: Asian longhorned beetle, chestnut blight, gypsy or spongy moths, Dutch elm disease, Phytopthora cinnamomi. Many invasive plant species present in the United States are also listed. These bioinvaders have not elicited the same level of response.]
According to a US Department of Agriculture report (USDA 2018), feral hogs only recently spread throughout the United States. In 1982, they were thought to inhabit only a small percentage of counties in 17 states. As of 2018, they were recognized as present in ~ 43% of all counties in the country; those counties were in 38 states and three US territories. USDA APHIS lists the following impacts from feral hog activities: damage to crops (including tree seedlings), livestock pastures and feed supplies, other kinds of property, and natural resources. In addition, feral pigs might transmit disease to the human food supply and possibly to livestock, and occasionally threaten public safety. In response, APHIS proposed to develop a national response. The goal was to reduce the risks and damages and encourage better coordination among the states and with Canada and Mexico. Since environmental conditions and laws vary among states, APHIS provides resources and expertise while allowing operational flexibility. The early focus was on primarily northern states where eradication was considered viable. By 2019, Idaho, Iowa, Maine, New Jersey, and New York had been declared “pig free”.
The Feral Swine Eradication and Control Pilot Program was officially established as by the 2018 Farm Bill. It was funded at $75 million over the five-year life of the 2018 Farm Bill – or ~$15 million per year. The program is implemented jointly by USDA Natural Resources Conservation Service (NRCS) and APHIS. According to the website, USDA focused these efforts where feral swine pose the highest threat.
APHIS has published a report covering the initial 2014 – 2018 program. I expect they will shortly publish a report covering 2018- 2023. My quick review of the available but outdated report shows that nearly all the pig removal projects funded by the program aimed to protect property, particularly agriculture. Protection of natural resources benefited from far fewer projects. The states funding natural resource projects most generously were Washington (92% of projects!); Illinois (62%); Nevada (48%); Florida (47%); Idaho and Missouri (both at 44%); Wisconsin and New Hampshire (both at 41%); Ohio (35%); Utah (34%); and Arizona (32%). Some of the Western states have considerable land managed by federal agencies; this might explain their relative focus on natural resources. Pennsylvania allocated only 1% of its projects to protecting natural resources. West Virginia and the U.S. Virgin Islands allocated none. I hope this tilt lessens in more recent years – although the program will clearly always be focused on agriculture.
There were no programs in five states: Massachusetts, Montana, Nebraska, South Dakota, and Wyoming.
Note that the summary of the draft Senate Farm Bill says this program would be funded at $75 million per year in future. This would increase funding 15 fold. I think this is probably a mistake in writing the summary; that the total funding would continue to be $75 million over five years.
I also reviewed the annual report issued by the APHIS Wildlife Services program’s National Wildlife Research Center (NWRC). The Center lists 17 publications by NWRC staff and cooperators dealing with various aspects of feral pig management [other than swine fever transmission]. Topics included feral pigs’ social structure; factors that influence reproductive rates; factors that influence efficacy of bait/trap programs; in-field methods to determine animal’s weight; and the extent to which hunters, farmers and the public accept various control techniques.
feral hog damage in a corn field; photo by Craig Hicks, USDA APHIS
Two of the studies – Didero et al. and VerCauteren et al. – aim to answer a fundamental economic question of feral hog management: how to determine the level of damage feral hogs cause to agricultural crops. Interestingly, authors of both studies conclude that existing data do not allow that determination. According to VerCauteren et al., understanding of wild pig damage is limited largely to one kind of damage — rooting – as it affects some natural resources (e.g., wetlands), some crops (e.g., grains, nuts, and beans), and some property (e.g., golf courses and cemeteries). They found few reports documenting damage from other behaviors or effects on pasture, livestock, sensitive species, public recreation spaces, and historical sites. Furthermore, they could not generalize the findings of even those studies that attempt to link the level of damage to pig population density. This is because these studies use many different metrics. They say that designing studies to capture the full scope of damage even in a local area will be complex because of the variety of resources at risk and of mechanisms by which damage might occur (e.g., rooting, consuming plants or animals, wallowing …). VerCauteren et al. suggest specific approaches that should be applied in future studies so that economic estimates will be consistent, shareable, and repeatable. I encourage you to read the articles to learn details of what is known about feral hog damage.
I rejoice that one set of NWRS studies focuses on Missouri. As I have blogged previously, Missouri has operated an aggressive program since the 1990s. I appreciate that APHIS is trying to learn how Missouri officials determined which approaches work best, and built support for the program among farmers, landowners, hunters, etc.
NWRC staff and cooperators also studied some other issues relating to invasive species impacts. One study sought to predict the level of suppression of brown treesnakes that must be achieved to protect birds that might be reintroduced on Guam. A second study sought to find out whether invasive coqui frogs can survive in the colder climates of high elevations in Hawai`i. There is concern that the frogs might compete with native birds for food.
SOURCES
Didero, N.M., K.H. Ernst, S.C. McKee, and S.A. Shwiff. 2023. A call and suggested criteria for standardizing economic estimates of wild pig damage. Crop Protection 165:106149. doi: 10.1016/j.cropro.2022.106149
United States Department of Agriculture National Feral Swine Damage Management Program Five Year Report FY14 – FY18
United States Department of Agriculture Animal and Plant Health Inspection Service Wildlife Services. 2024. Innovative Solutions to Human Wildlife Conflicts. National Wildlife Research Center Accomplishments, 2023.
VerCauteren, K.C., K.M. Pepin, S.M. Cook, S. McKee, A. Pagels, K.J. Kohen, I.A. Messer, M.P. Glow, N.P. Snow. 2024. What is known, unknown, and needed to be known about damage caused by wild pigs. Biol Invasions (2024) 26:1313–1325 https://doi.org/10.1007/s10530-024-03263-z
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
invasion of wild/black mustard Brassica nigra; photo by carlbegge via Flickr
A California state legislator has proposed a bill to expand state efforts to counter invasive species. Should we support it – and others like it in other states?
The bill is Assembly Bill 2827 introduced by Assembly Member (and former Majority Leader) Eloise Reyes of the 50th Assembly District. She represents urban parts of southwestern San Bernardino County, including the cities of Rialto, Colton, and Fontana.
According to media reports, Reyes was prompted to act by the current outbreak of exotic fruit flies, which as of some months ago resulted in detections in 15 California counties.
The bill is much broader than agricultural pests, however. It would find and declare that it is a primary goal of the state to prevent the introduction, and suppress the spread, of invasive species within its borders. I applaud the language of the “findings” section:
(a) Invasive species have the potential to cause extensive damage to California’s natural and working landscapes, native species, agriculture, the public, and economy.
(b) Invasive species can threaten native flora and fauna, disrupt ecosystems, damage critical infrastructure, and result in further loss of biodiversity.
Paragraph (c) cites rising threats associated with increased movement of goods, international travel, and climate change — all said to create conditions that may enhance the survival, reproduction, and spread of these invasive species, posing additional threats to the state.
(d) It is in the best interest of the state to adopt a proactive and coordinated approach to prevent the introduction and spread of invasive species.
California sycamore attacked by invasive shot hole borer; photo by Beatriz Nobua-Behrmann
The bill calls for
The state agencies, in collaboration with relevant stakeholders, to develop and implement pertinent strategies to protect the state’s agriculture, environment, and natural resources.
The state to invest in research, outreach, and education programs to raise awareness and promote responsible practices among residents, industries, and visitors.
State agencies to coordinate efforts with federal, local, and tribal authorities.
However, the bill falls short when it comes to action. Having declared that countering bioinvasion is “a primary goal of the state”, and mandated the above efforts, the bill says only that the California Department of Food and Agriculture (which has responsibility for plant pests) is to allocate funds, if available, to implement and enforce this article. Under this provision, significant action is likely to depend on holding agencies accountable and providing increased funding.
removing coast live oak killed by goldspotted oak borer; photo by F.T. Campbell
Would this proposed legislation make a practical difference? I have often complained that CDFA has not taken action to protect the state’s wonderful flora. For example, CDFA does not regulate firewood to prevent movement of pests within the State. It has not regulated numerous invasive plants or several wood-boring insects. These include the goldspotted oak borer; the polyphagous and Kuroshio shothole borers; and the Mediterranean oak borer.
On the other hand, CDFA is quick to act against pests that might enter the state from elsewhere in the country, e.g., spongy moth (European or Asian), emerald ash borer and spotted lanternfly.
I hope Californians and the several non-governmental organizations focused on invasive species will lobby the legislature to adopt Assembly Bill 2827. I hope further that they will try to identify and secure a source of funds to support the mandated action by CDFA and other agencies responsible for managing the fauna, flora, and other taxa to which invasive species belong.
I applaud Ms. Reyes’ initiative. I hope legislators in other states will consider proposing similar bills.
Posted by Faith Campbell
We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.
For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm
