Feral hog eradication – making progress by doing it the right way

large_hog_damage (MO)

feral hogs in Missouri

As I wrote in my blog of March 2016, introduced wild hogs (Sus scrofa) threaten ecosystems across the continent and on islands ranging from Hawai`i to the Caribbean.

According to an environment impact statement prepared by APHIS (see reference below), these highly adaptable, prolific, large and powerful animals cause immense damage by rooting for plant parts and invertebrates in the soil, and by wallowing to cool themselves and fend off biting insects. Pigs may root to depths of three feet below the surface. Wallows are commonly located in or adjacent to riparian or bottomland habitats. Feral hogs out-compete other animals for hard mast and also consume algae, fungi, soil invertebrates, worms, crustaceans, and bird and reptile eggs. They even feed on small vertebrate animals.

Rising feral hog populations and spread to new areas has raised concern. insert map  According to John J. Mayer (reference below), the number of states with established wild boar populations is now 37. They might number as many as 11.3 million. Texas has the largest numbers, 30 to 41% of the U.S. total. Other states with high numbers are Alabama, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, Oklahoma, and South Carolina.


Poison them?

One proposed response was to poison the hogs using the anticoagulant drug Warfarin – which is widely used as a rodent poison. The U.S. Environmental Protection Agency (EPA) approved the use of warfarin as a bait – Kaput® Feral Hog Bait – in January 2017 after only 16 months of review – an unprecedented brief period for a toxin. Many expressed concern, especially about possible poisoning of non-target wildlife. The National Environmental Coalition on Invasive Species was one of several groups to ask EPA to reconsider.  Principal concerns raised: black bears and other wildlife could open the bait dispenser; spilled bait could be eaten by a wide variety of wildlife; scavengers could be exposed when they feed on the carcasses of poisoned pigs; hunters could also be exposed to contaminated meat. Several states considering use of the bait – including Louisiana and Texas – decided to reconsider. The Arkansas Game and Fish Commission also asked the state Plant Board to take care pending additional study of the secondary effects.

Missouri Program Expands

Meanwhile, Missouri is finding success with its aggressive and scientifically-based program, which began  years ago in response to growing public concern about hog damage. As I noted in my earlier blog, in 2016, the Missouri Conservation Commission prohibited hunting of feral hogs on lands owned, leased, or managed by the Missouri Department of Conservation. Missouri took this action because hunting does not significantly reduce feral hog populations. Instead, it causes the animals to disperse – making them even more difficult to control. (Missouri has extensive material on feral hogs posted here  .

The Missouri Department of Conservation is working with several partners – including other government agencies, non-government organizations, agricultural organizations and many landowners. The program has included private lands since the 1990s. However, there is an increased effort to engage more private landowners so as to place traps on more lands in the state. The outreach includes landowner workshops and presentations to various groups, as well as information provided at fairs and similar events. MDC relies largely on landowners contacting the agency when they have feral hog problems and visits to individuals.

The outreach is working; the number of landowners asking for assistance is rising.

The numbers of hogs removed has also risen. During 2016, 5,358  were removed as part of the program. During the first seven months of 2017, From January 1 through July 31, 2017 MDC and its partners removed 4,703 feral hogs.  This is more than a thousand more than had been removed during the same period in 2016.

The program is not cheap; the Conservation Commission approved $1.8 million for fiscal year 2018. These funds cover primarily trapping and killing activities. Costs for MDC staff time and fuel are not included. Most of the MDC staff assisting the program do so as an additional duty. Recently, MDC has hired Mark McLain as the Feral Hog Elimination Team Leader to coordinate MDC feral hog elimination efforts statewide.

Information for this blog came in part from an MDC press release here  and Alan Leary and Mark McLain of the Missouri Department of Conservation. However, the views presented here are those of the Center for Invasive Species Prevention, not the Missouri Department of Conservation.



Mayer, J.J. 2014. Estimation of the Number of Wild Pigs Found in the Unted States. August 2014 SRNL-STI-2014-00292, Revision 0.


U.S. Department of Agriculture Animal and Plant Health Inspection Service Final Environmental Impact Statement. Feral Swine Damage Management: a National Approach May 27, 2015 https://www.aphis.usda.gov/regulations/pdfs/nepa/2015%20Final%20EIS%20Feral%20Swine%20Damage%20Management%20-%20A%20National%20Approach.pdf


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.


Posted by Faith Campbell

California – volunteers make major efforts

polyphagous shot hole borer exit holes on box elder; photo source http://ucanr.edu/

I have posted many blogs criticizing California state authorities for not acting to counter several highly damaging tree-killing pests, such as the goldspotted oak borer and invasive shot hole borers.

I should have made it clear that many Californians – academics, employees of local, state, and federal agencies, concerned citizens – are working very hard to develop scientific knowledge, test strategies, educate stakeholders and those whose activities facilitate the insects’ spread. These people have carried forward a wide range of dedicated efforts that do much to make up for the lack of state or federal agencies’ engagement.

More than 60 stakeholder entities now participate in one or more of nine working groups focused on shot hole borers, promoting research, education and outreach. Some of these activities receive advice (but apparently no funding) from California Department of Food and Agriculture. Outreach to the media has resulted in some good coverage. Master Gardeners and other potential citizen scientist groups have been trained. See here.

A smaller but older group is carrying out similar activities targetting goldspotted oak borer; visit here.


Here I summarize some of the most recent activities.

1) Scientists have released a pocket-sized guide for identifying trees infested by polyphagous or Kuroshio shot hole borers (For summaries of the threat posed by these insects and their associated fungi, visit here). The guide can be downloaded here.

The Guide is useful for people outside as well as inside California, since some host species grow across the continent: box elder (Acer negundo), sweetgum (Liquidambar styraciflua), tree of heaven (Ailanthus altissima), mimosa or silk tree (Albizia julibrissin).

Other hosts are common in horticulture: camellia (Camellia semiserrata), Japanese maple (Acer palmatum), Japanese wisteria (Wisteria floribunda), London plane (Platanus x acerifolia), mimosa, and weeping willow (Salix babylonica).

The shot hole borers could be present outside the six California counties known to contain infestations because one or both of these beetles could have been spread via movement of wood, greenwaste, or nursery stock; or they could have entered other parts of the country on plants or wood from Asia.


2) Scientists are testing possible pesticide treatments to protect trees from polyphagous shot hole borer

The polyphagous shot hole borer (a still undescribed beetle in the Euwallacea genus), attacks more than 200 host tree species in southern California, including many important native and urban landscape trees. Forty-nine species from more than 20 families are known to be reproductive hosts. Trees are dying in parks, residential neighborhoods, other public landscapes, and riparian areas.  John Boland of Southwest Wetlands Interpretive Association has documented that 88% of the willows in the Tijuana River Valley have been infested by the Kuroshio shot hole borer – although many of the trees regrow into four-foot-tall shrubs. Dr. Boland estimates that more than two billion KSHB hatched in the valley during 2015-2016.

Confronted by such threats, home owners, park managers, and arborists are desperate for management tools.

As reported by Jones et al. 2017 (see reference below), scientists tested the effectiveness of insecticides, fungicides, and insecticide–fungicide combinations for controlling continued PSHB attacks on previously infested California sycamore trees. The combination of a systemic insecticide (emamectin benzoate), a contact insecticide (bifenthrin), and a fungicide (metconazole) provided the best control over the six months of the study period. The biological fungicide Bacillus subtilis provided short-term control.

Efficacy of the treatment combination is not yet settled. First, the polyphagous shot hole borer actively oviposits year-round, and both adults and larvae may be found in an infested tree at any time of year. Furthermore, the shot hole borers are active throughout the sapwood, not just in the phloem and cambium tissues. These differences in behavior may make timing and efficacy of systemic insecticides more difficult to predict. In addition, it is extremely difficult to detect infestations at an early stage, when treatment is most likely to be effective. Finally, the treated trees should be monitored over several years, rather than for six months, to evaluate true efficacy.


3) Efforts to gain official actions re: Invasive Shot Hole Borers

Some people are trying to promote state engagement. They are focused on getting adoption of a strategy under the auspices of the California Invasive Species Council to create a system to respond to bioinvaders that don’t fall within the California Department of Food and Agriculture’s definition of its responsibilities – e.g., the shot hole borers. The invasive shot hole borers are included in the interagency “Charting the Pest Prevention System in California” plan.


4)  On-the-Ground Efforts

Some entities are compiling and publicizing their costs for responding to the several wood borers. For example, the University of California Irvine reports spending close to $2 million to manage trees on campus that have been attacked. The Orange County parks agency has spent $1.7 million on shot hole borer surveys, tree inventory, public outreach materials, staff training, and some research. These costs are rising – in the first half of 2017, Orange County parks agency has already spent $348,000 on tree treatment and removal.

UC Cooperative Extension for San Diego County organized a Green Waste-Wood Biomass Symposium in February aimed at educating industry and public agency waste-management practitioner.

Goldspotted Oak Borer

Three National forests are treating high-value oaks in specific sites:

  1. Cleveland NF sprayed 248 oak trees with the contact insecticide, carbaryl. The Forest hopes to continue the treatments yearly dependent on funding and need.
  2. The Angeles NF removed 50 GSOB-infected oaks in Green Valley. They then tagged about 1,000 oak trees in the area so their changing conditions can be monitored.
  3. San Bernardino NF is felling and debarking GSOB-infested oaks on the periphery of the communities of Idyllwild and Pine Cove.

Orange County removed highly infested trees at Weir Canyon; now spraying another 1,672 oaks, including both lightly infested and neighboring trees, with carbaryl  … monitoring has not detected any other infested trees in Weir Canyon or neighboring Blind Canyon.


Summarized from the San Diego County update (reference below).

In the absence of legal mechanisms to stop the movement of infested firewood, collaborating organizations have focused on public education and outreach programs for the firewood industry, tree care professionals, and the public. Still, some infested wood continues to be moved – probably to uninfested areas.

The Update also reports the following impacts of the goldspotted oak borer in San Diego County:

  • Eight San Diego County Parks have suffered loss of habitat, diminished recreational value, and direct costs associated with tree removal and grinding and insecticidal treatments. More than 5,000 trees have been lost in just one park, William Heise Park.
  • One California State Park lost nearly $500,000 in campground and day-use fees when areas were closed for tree removal. GSOB has been discovered at two more State parks in recent years.
  • The Cleveland National Forest has suffered negative environmental, economic and aesthetic impacts; removed more than 200 trees and treated 248 high-value trees on developed sites.
  • Tribal lands have lost oaks of great cultural value as well as reduced habitat, shade, and recreational enjoyment.
  • Urban and rural residential homeowners are faced with removal and disposal costs averaging $1,500 per tree.
  • Fire, transportation, and public works agencies are dealing with higher fuel loads and hazard trees along rights of way.


GSOB activists are collaborating with those working on the invasive shot hole borers to seek state and federal support.


SOD-infected tanoak; photo by F.T. Campbell


Eight California nurseries were found late this spring to be infected by the sudden oak death pathogen (Phytophthora ramorum).  (As of May, only two nurseries were known to be positive.) Seven of the positive nurseries are located in counties with disease in the natural environment. Given the wet winter and spring in California, this upswing is probably not surprising. Still, this sudden upsurge raises questions about the efficacy of nursery regulations. One of the nurseries was detected as a result of a trace-back investigation – not through the annual inspection.


California Oak Mortality Task Force newsletter, July 2017

Goldspotted Oak Borer and Oak Mortality Quarterly Situation Report April 1 through June 30, 2017

Status of Goldspotted Oak Borer – July 2017 Update Goldspotted Oak Borer Steering Committee www.GSOB.org Email: gsobinfo@ucdavis.edu

 Invasive Shot Hole Borer (Polyphagous and Kuroshio)/Fusarium Dieback Quarterly Situation Report January 1 through March 31, 2017

Jones, M.E., J. Kabashima, A. Eskalen, M. Dimson, J.S. Mayorquin, J.D. Carrillo, C.C. Hanlon, and T.D. Paine. 2017. Evaluations of Insecticides and Fungicides for Reducing Attack Rates of a new invasive ambrosia beetle (Euwallacea Sp., Coleoptera: Curculionidae: Scolytinae) in Infested Landscape Trees in Calif. Journal of Economic Entomology, 110(4), 2017, 1611–1618 doi: 10.1093/jee/tox163 Advance Access Publication Date: 5 July 2017


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.

Posted by Faith Campbell

Thank Your Senators!!!


Congress is now considering funding for various agencies and programs for Fiscal Year 2018 – which begins on October 1, 2017. Both the House and Senate Appropriations committees have adopted bills to fund APHIS (in the agriculture appropriations bill) and USFS (in the interior appropriations bill). Once these are passed – I expect with little change – by the appropriate chambers, the two very different bills will be reconciled by a Conference Committee made up of members of both the House and Senate and then passed in final form.

Please thank the Senators on the Agriculture Appropriations Subcommittee for their strong support for APHIS’ programs targeting tree pests. Ask them to maintain this support during the Conference – where the House members will be pushing for cuts.

To read the bills and accompanying reports, go here for the House appropriations bill for USDA, (including APHIS); here for the House Interior bill (including the USFS).  Go here for the Senate appropriation bill for USDA.  (Links to the bills and reports are at the end of each press release.) The Senate Appropriations Committee has not yet acted on the Interior bill.


Animal and Plant Health Inspection Service

Appropriators are working under severe pressure given the large spending reductions proposed by the President in the Administration’s budget sent to the Congress earlier in the Spring.

The House appropriated $906 million for APHIS. This is $40 million less than in FY17 but $96.4 million more for APHIS than the Administration requested. The House agriculture appropriations bill made significant cuts in the Tree and Wood Pests program in order to stay within its overall total while maintaining or expanding other programs. The result would devastate the Tree and Wood Pests program. The House bill cuts funding for this program by 30% from the level provided in recent years – from $54 million to $38 million.

The Senate bill, in contrast, increases funding for the Tree and Wood Pests program by $2 million – from $54 million to $56 million. The Senate was able to do this because its bill provided significantly more money for APHIS than did the House: the Senate bill appropriated $953.2 million for APHIS, $7 million above the FY17 funding level; $143.2 million above the Administration’s budget request; and $47 million above the House funding level.

I have blogged often about the necessity of maintaining the Tree and Wood Pest program. In recent years, APHIS’ Asian longhorned beetle (ALB) eradication program has cost $35 – $40 million per year. The program has succeeded in shrinking the New York infestation by 85% and the Massachusetts infestation by 34%. The Ohio infestation has also been reduced – although by considerably less. In its FY2016 annual report, APHIS said the infestation area had been cut by 15%. However, earlier in July APHIS announced that the Ohio infestation is larger than previously known. The quarantine zone was expanded from 61 to 62 square miles. Now is not the time to abandon the 21-year old ALB eradication effort. For a reminder of the threat this insect poses to our hardwood trees, see the write-up here.

The report from the Senate Committee link says that it is “essential” to complete eradication of the ALB.

APHIS and the states have already agreed to cut back the agency’s efforts to regulate movement of ash wood in order to slow the spread of the emerald ash borer (EAB). I am unhappy about this retreat. Still, APHIS planned to continue to survey for EAB in unregulated areas, to educate appropriate publics, to coordinate with affected states, and to produce and disperse biocontrol agents. The Senate funding level – unlike the House funding level – would allow APHIS to maintain these vitally important activities aimed at protecting America’s urban and wildland forests from EAB (For a reminder of that threat, see the write-up here).

Finally, states and stakeholders will expect APHIS to continue its program to slow the spread of the gypsy moth – a program which has received from the Tree and Wood Pest program $5 – $6 million per year in recent years. APHIS must also be prepared to eradicate any newly detected outbreaks, especially of the Asian gypsy moth on the West coast.

I have repeatedly argued that APHIS should expand its program so as to address the many additional tree-killing pests introduced in recent years, including

  • Redbay ambrosia beetle / laurel wilt disease
  • Sirex woodwasp
  • Goldspotted oak borer
  • Walnut twig beetle and thousand cankers disease
  • Soapberry borer
  • Polyphagous & Kuroshio shot hole borers
  • Velvet longhorned beetle
  • Spotted lanternfly

Therefore, I rejoice to see that the Senate report link says: “The Secretary is directed to report to the Committee regarding the steps being taken to eradicate the Asian long-horned beetle and spotted lanternfly and to minimize the spread of other pests such as the polyphagous and Kuroshio shot hole borers (emphasis added).

The Senate report also calls on APHIS to continue efforts to control the coconut rhinoceros beetle in Hawai`i and Ceratocystis disease  That latter is presumably the pathogen causing rapid `ohi`a death in Hawai`i.

The other APHIS program which has supported programs targetting tree-killing pests is the Specialty Crops program. The House bill increased funding for the Specialty Crops program from $156 million to $160 million for FY18. However, $152.3 million of this total – 95% — is allocated to specified agricultural pests, including fruit flies, diseases of citrus trees, glassy winged sharpshooter and European grape vine moth, pale cyst nematode, and light brown apple moth. This means that little is left for addressing sudden oak death or tree-killing pests next year.

Strangely, APHIS said, in its FY16 Annual Report, that the European grape vine moth had been eradicated. So why does the FY18 House appropriations bill allocate $5 million for this pest? It might be for continued surveillance to verify that eradication has been successful.

The Senate bill provides even more – $166 million – for the Specialty Crops program.  The Senate Committee report instructs APHIS to spend “no less than the fiscal year 2017 level of funding” to manage potential movement of sudden oak death in the nursery trade – without specifying the amount.

The House committee did expand overall funding for plant pests to a total of $294 million. The House report says that this total includes an increase of $12.5 million for a Plant Pest and Disease Management and Disaster Prevention Program. This funding explicitly can be spent on tree and wood pest surveillance as well as the clean plant network and citrus health. This increase is welcome, but it does not make up for the 30% cut in specific funding for the tree and wood pest program. The increased surveillance is of doubtful value if it does not result in eradication or containment efforts!

Again, the Senate bill is more generous; it provides $320,308,000 for plant health.

The decisions made by the House Appropriations Committee clearly show the importance of lobbying by traditional agricultural interests in defending funding for programs of interest to them. Several programs targetting diseases of livestock and poultry were maintained at the FY17 funding level. As noted above, the “specialty crop pests” account was increased.


Those of us who care about protecting our trees must become more visible advocates for these programs.


As in the past, both the House and Senate reports support APHIS’ access to emergency funding to be obtained as transfers from the Commodity Credit Corporation for the “arrest” and eradication of animal and plant pests and diseases that threaten American agriculture. The House language appears to be less restrictive.

Unfortunately, it has been years since APHIS sought – much less received – funding through the emergency provision to address tree-killing pests. This is why CISP and others are proposing to amend the Farm Bill to broaden APHIS’ authority to access these funds when appropriated funds are insufficient to counter tree-killing pests. (See my blog from early July for information about these proposed amendments and how you can support them.)

The House also follows the Administration in calling for greater cost-sharing with States and other cooperators. The Houe report states: “The Committee directs APHIS to maximize the use of cost-sharing agreements or matching requirements with states, territories, producers, foreign governments, non-governmental organizations, and any other recipient of services in order to reduce the cost burden on the agency.”

The President’s budget request called for even more severe cuts and justified these cuts by saying that the programs could be maintained if the states, localities, and industries benefitting from eradication or containment of the ALB and EAB helped pay for the containment program. The budget called for beneficiaries to pay 50% of program costs. However, states, localities, and industries are very unlikely to make up such severe cuts in funding. Already, local governments across the country are spending more than $3 billion each year to remove trees on city property killed by non-native pests. Homeowners are spending $1 billion to remove and replace trees on their properties and are absorbing an additional $1.5 billion in reduced property values and reducing the quality of their neighborhoods (Aukema et al. 2011; full reference at end of blog.)

Remember: thank your senators for their generosity to APHIS’ tree pest programs – especially if they are members of the Senate Agriculture Appropriations subcommittee (members listed below).

John Hoeven, North Dakota

Thad Cochran, Mississippi

Mitch McConnell, Kentucky

Susan Collins, Maine

Roy Blunt, Missouri

Jerry Moran, Kansas,

Marco Rubio, Florida

Jeff Merkley, Oregon

Diane Feinstein, California

Jon Tester, Montana

Tom Udall, New Mexico

Patrick Leahy, Vermont

Tammy Baldwin, Illinois




US Forest Service

The House Interior Committee provided $92,084,000 for Forest Health Management, $2,416,000 below the FY17 funding level but $1,694,000 above the budget request. The Report does not specify the amounts for federal v. non-federal lands, but the Administration’s request specified $54 million for federal lands and $36 million for cooperative programs managing forests on non-federal lands. (As recently as FY2014, the forest health program received more than $100 million per year.)

The House Interior Committee recommends $278,368,000 for Forest and Rangeland Research, $10,146,000 below the FY 2017 funding level and $19,368,000 above the budget request. $75 million  of this total is allocated to the Forest Inventory and Analysis program. The Report says that the Committee does not accept the proposed reduction for invasive species research. This is gratifying. However, I have been unable to find the proposed reduction, and there has never been a “line” specifically for invasive species research. Therefore, I am unclear about what level of funding has been retained. (In past years, the total allocated to research on non-native tree-killing pests averaged about $5 million.)

The Senate Appropriations Committee has not yet acted on the Interior Appropriations bill so I cannot tell you how much money that body will provide for these programs.




Aukema, J.E., B. Leung, K. Kovacs, C. Chivers, K. O. Britton, J. Englin, S.J. Frankel, R. G. Haight, T. P. Holmes, A. Liebhold, D.G. McCullough, B. Von Holle.. 2011. Economic Impacts of Non-Native Forest Insects in the Continental United States PLoS One September 2011 (Volume 6 Issue 9)



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.

Posted by Faith Campbell


Invasive “hot spot” study confirms vulnerable places, causes of introductions

removing Miconia from Hawaiian forest; courtesy of the Nature Conservancy of Hawai`i

A recent article by Wayne Dawson and 24 coauthors (see reference at the end of this blog) provides the first-ever global analysis of established alien species. They studied the diversity of established alien species belonging go eight taxonomic groups – amphibians, ants, birds, freshwater fish, mammals, reptiles, spiders and vascular plants – across 609 regions (186 islands or archipelagos, and 423 mainland regions).

The analysis found that the highest numbers of established alien species in these taxonomic groups were in the Hawaiian Islands, New Zealand’s North Island and the Lesser Sunda Islands of Indonesia. The Hawaiian Islands have high numbers of invasive species in all of the eight groups studied. In New Zealand, the highest numbers were invasive plants and introduced mammals that prey on the native birds.

Florida is the top hotspot among mainland regions. Florida is followed by the California coast and northern Australia.

Burmese python in the Florida Everglades; photo by U.S. Fish & Wildlife Service


 Invasive species hotspots were found mainly on islands and in coastal regions of mainland areas. The lead author, Dr. Wayne Dawson, a researcher at Durham University’s Department of Biosciences, suggested that the greater invasive species richness in coastal regions probably results from higher rates of species introductions to port areas compared to interior regions.

Island regions have, on average, higher cross-taxon invasive species richness. This cross-taxon richness on islands tends to be higher for those islands further from continental landmasses. The authors suggest that such oceanic islands might be more likely to import large quantities of goods from foreign sources than islands close to continents, thus experiencing higher propagule pressure.



Regions with greater wealth (measured as per capita GNP), human population density, and area have higher established alien richness. These effects were strongest on islands. The authors suggest that wealth and human population density might correlate with higher numbers of species being brought to the region through trade and transport.

On mainlands, cooler regions have higher richness. I think this might reflect history – centuries of colonial powers importing plants and animals. However, colonial powers also introduced species to tropical regions.  In contrast, on islands warmer and wetter regions have higher richness of invasive species.



The authors conclude that cumulative numbers of invasive species at a particular location are driven to a greater extent by differences in area and propagule pressure than by climate. The model that best explains cross-taxon invasive species richness combines per capita GDP, population density and sampling effort. Other important factors are area of the region, mean annual precipitation, and whether a region is on a mainland or island(s).

The study results show that, per unit increase in area, per capita GDP, and population density, invasive species richness increases at a faster rate on islands than on mainlands. This might be confirmation of the longstanding belief that islands are more readily invaded than mainlands, although the authors caution that a rigorous test of this explanation would require data on failed introductions.

The authors call for additional research to understand whether these effects arise because more species are introduced to hotspot regions, or because human disturbance in these regions makes it easier for the newcomers to find vacant spaces and opportunities to thrive.


I think it would be helpful to compare the findings on invasive species richness in specific regions to data on historic patterns of trade and colonization to strengthen our understanding of the importance of propagule pressure in determining invasion patterns.


Increasing Confirmation of Significance and Breadth of Invasive Species Threat

The Dawson et al. study is the latest in a series of analyses of global or regional patterns in invasive species. I have blogged previously about several of these:

  • Bradshaw et al. 2016 concluded that invasive insects alone cause at least $77 billion in damage every year, a figure they described as a “gross underestimate”.
  • A study by Hanno Seebens and 44 coauthors showed that the rate of new introductions of alien species has risen rapidly since about 1800 – and shows no sign of slowing down. Adoption of national and international biosecurity measures have been only partially effective, failing to slow deliberate introductions of vascular plant species, birds, and reptiles, and accidentally introduced invertebrates and pathogens. Like Dawson et al, Seebens et al. found a strong correlation between the spread of bioinvaders introduced primarily accidentally as stowaways on transport vectors or contaminants of commodities (e.g., algae, insects, crustaceans, molluscs and other invertebrates) and the market value of goods imported into the region of interest.
  • Liebhold et al. 2016(see reference below) studied insect assemblages in 20 regions around the world. They found that an insect taxon’s ability to take advantage of particular invasion pathways better explained the insect’s invasion history than the insects’ life-history traits. (The latter affect the insect’s ability to establish in a new ecosystem.)
  • Maartje J. Klapwijk and several colleagues note that growing trade in living plants and wood products has brought a rise in non-native tree pests becoming established in Europe. The number of alien invertebrate species has increased two-fold since 1950; the number of fungal species has increased four-fold since 1900.
  • Jung et al. (2015) studied the presence of Phytophthora pathogens in nurseries in Europe. They found 59 putatively alien Phytophthora taxa in the nurseries. Two-thirds were unknown to science before 1990. None had been intercepted at European ports of entry when they were introduced. Nor have strict quarantine regulations halted spread of the quarantine organism ramorum.
  • A report by The World Conservation Union (IUCN) on World Heritage sites globally found that invasive species were second to poaching as a threat to the sites’ natural values. Of 229 natural World Heritage sites examined, 104 were affected by invasive species. Island sites – especially in the tropics – were most heavily impacted.
  • Another report by IUCN found that invasive species were the second most common cause of species extinctions – especially for vertebrates.


These studies demonstrate that

  • Invasive species have become a significant threat to biological diversity and ecosystem services around the world – one that continues to grow.
  • The recent spate of studies originating in Europe probably reflects recent recognition of the continent’s vulnerability – as seen, inter alia, in the proliferation of tree-killing Phytophthoras.
  • Human movement of species – propagule pressure – whether deliberately or due to inadequate efforts to manage trade-related pathways – explain the bulk of “successful” introductions.
  • Economic activity drives introductions, so areas at highest immediate risk are urban areas and other centers receiving high volumes of imports and visitors. Among troubling trends in the future is rapid global urbanization – along with rising economic interdependency.
  • Efforts to curb these movements – at the national, regional, and international levels – have failed so far to counter the threat posed by invasive species of nearly all taxonomic groups.

In my view, the requirements that phytosanitary measures “balance” pest prevention against trade facilitation results in half measures being applied – and half measures achieve halfway results. For example, the U.S. does not require that packaging be made from materials that cannot transport tree-killing pests. The USDA has moved far too slowly to limit imports of plant taxa that pose a risk of either being invasive themselves or of transporting pests known to be damaging.


Conservationists should focus on building political pressure to strengthen regulations and other programs intended to curtail this movement. No other approach will succeed.



Bradshaw, C.J.A. et al. Massive yet grossly underestimated global costs of invasive insects. Nat. Commun. 7, 12986 doi: 10.1038/ncomms12986 (2016). (Open access)

Dawson, W., D. Moser, M. van Kleunen, H. Kreft, J. Perg, P. Pyšek, P. Weigelt, M. Winter, B. Lenzner, T.M. Blackburn, E.E. Dyer, P. Cassey, S.L. Scrivens, E.P. Economo, B. Guénard, C. Capinha, H. Seebens, P. García-Díaz, W. Nentwig, E. García-Berthou, C. Casal, N.E. Mandrak, P. Fuller, C. Meyer and F. Ess. 2017. Global hotspots and correlates of IAS richness across taxon groups. Nature Ecology and Evolution Vol. 1, Article 0186. DOI: 10.1038/s41559-017-0186 | www.nature.com/natecolevol


Jung,T., L. Orlikowski, B. Henricot, P. Abad-Campos, A.G. Aday, O. Aguin Casa, J. Bakonyi, S.O. Cacciola, T. Cech, D. Chavarriaga, T. Corcobado, A. Cravador, T. Decourcelle, G. Denton, S. Diamandis, H.T. Doggmus-Lehtijarvi, A. Franceschini, B. Ginetti, M. Glavendekic, J. Hantula, G. Hartmann, M. Herrero, D. Ivic, M. Horta Jung, A. Lilja, N. Keca, V. Kramarets, A. Lyubenova, H. Machado, G. Magnano di San Lio, P.J. Mansilla Vazquez, B. Marais, I. Matsiakh, I. Milenkovic, S. Moricca, Z.A. Nagy, J. Nechwatal, C. Olsson, T. Oszako, A. Pane, E.J. Paplomatas, C. Pintos Varela, S. Prospero, C. Rial Martinez, D. Rigling, C. Robin, A. Rytkonen, M.E. Sanchez, B. Scanu, A. Schlenzig, J. Schumacher, S. Slavov, A. Solla, E. Sousa, J. Stenlid, V. Talgø, Z. Tomic, P. Tsopelas, A. Vannini, A.M. Vettraino, M. Wenneker, S. Woodward and A. Perez-Sierra. 2015. Widespread Phytophthora infestations in European nurseries put forest, semi-natural and horticultural ecosystems at high risk of Phytophthora disease. Forest Pathology.


Klapwijk, M.J., A.J.M. Hopkins, L. Eriksson, M. Pettersson, M. Schroeder, A. Lindelo¨w, J. Ro¨nnberg, E.C.H. Keskitalo, M. Kenis. 2016. Reducing the risk of invasive forest pests and pathogens: Combining legislation, targeted management and public awareness. Ambio 2016, 45(Suppl. 2):S223–S234  DOI 10.1007/s13280-015-0748-3  [http://www.nature.com/articles/ncomms14435 ]


Liebhold, A.M., T. Yamanaka, A. Roques, S. Augustin, S.L. Chown, E.G. Brockerhoff, P. Pysek. 2016. Global compositional variation among native and nonindigenous regional insect assemblages emphasizes the importance of pathways. Biological Invasions (2016) 18:893–905


Seebens, H. et al., 2017. No saturation in the accumulation of alien species worldwide. Nature Communications. January 2017. [http://www.nature.com/articles/ncomms14435 ]



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.


Posted by Faith Campbell



How we can strengthen programs to protect trees from invasive pests

USDA; photo by F.T. Campbell

Every five years, Congress adopts a new Farm Bill. The House and Senate Agriculture committees are  holding hearings and considering proposals for the Farm Bill due to be adopted in 2019. Now is the time for people concerned about the continuing introductions of forest pests and weakness of our government’s response to pests that have become established to ask their Representative and Senators to adopt legislative language to strengthen relevant USDA programs. I suggest specific proposals below – which I hope you will urge your representatives to support.

The Farm Bill supports our Nation’s largest soil and water conservation programs. The Farm Bill can also be used to create new programs that address other issues – such as pest prevention and response.

The Farm Bill already has been used to strengthen APHIS’ phytosanitary programs. For example, Section 10007 of the 2014 Farm Bill provides more than $50 million annually for the Plant Pest and Disease Management and Disaster Prevention Program. These funds have supported numerous vitally important research and management programs targetting polyphagous shot hole borer, spotted lanternfly, velvet longhorned borer, thousand cankers disease, emerald ash borer, as well as more general goals such as improving traps for detecting wood-borers and outreach about emerald ash borer to Native American tribes. With APHIS’ annual appropriations falling far short of the resources needed to respond to invasions by numerous plant pests, Section 10007 has provided essential supplements to the agency’s programs.

The new Farm Bill to be adopted by the Congress offers opportunities to strengthen other components of USDA programs with the goal of protecting the tree species comprising our wildland, rural, and urban forests.

The Center for Invasive Species Prevention and Vermont Woodland Owners Association have developed several proposals that we hope will be incorporated into the 2019 Farm Bill. These proposals have been endorsed by the Reduce Risk from Invasive Species Coalition.  The amendments have also been endorsed by the Weed Science Society of America. CISP submitted testimony summarizing these proposals to the Senate Committee on Agriculture, Nutrition, and Forestry in early July, when the Committee held a hearing on the Farm Bill’s conservation and forestry programs. (For a copy of our testimony, contact us using the “contact us” button.)

You can help by contacting your Representative and Senators and asking them to support these proposed amendments to the 2019 Farm Bill.

These proposed amendments seek to address the following needs.

  • Do you wish to strengthen APHIS’ commitment to pest prevention in the face of a competing mandate to facilitate trade?

Then you might want to support a proposed amendment to Section 3 of the Plant Protection Act. The new language would read as follows:

“(3) It is the responsibility of the Secretary to facilitate exports, imports and interstate commerce in agricultural products and other commodities that pose a risk of harboring plant pests or noxious weeds in ways that will reduce prevent, to the greatest extent practicable feasible, as determined by the Secretary, the risk of dissemination of plant pests and noxious weeds.”

  • Do you wish to increase funding for APHIS’ programs responding to recently-detected plant pests?

Then you might want to support a proposed amendment that would expand APHIS’ access to emergency funds by enacting a broad definition of “emergency”. Under the new definition, “emergency” would mean “any outbreak of a plant pest or noxious weed which directly or indirectly threatens any segment of the agricultural production of the United States and for which the then available appropriated funds are determined by the Secretary to be insufficient to timely achieve the arrest, control, eradication, or prevention of the spread of such plant pest or noxious weed.”

This amendment would help APHIS evade the downward push of its declining annual appropriation and enable the agency to tackle more of the tree-killing pest that have entered the U.S.

Customs inspecting wood packaging

  • Do you wish to promote stronger measures aimed at minimizing the presence of pests in wood packaging material? (I have blogged repeatedly about the continuing pest risk associated with the wood packaging pathway.)

Then you might want to support a proposed amendment that would establish a non-governmental Center for Agriculture-Trade Partnership Against Invasive Species. That Center would promote industry best practices, encourage information-sharing, and create an industry certification program under which importers would voluntarily implement pest-prevention actions that are more stringent than current regulations (ISPM#15) Link require.

American Chestnut Foundation chestnut in experimental planting in Fairfax County, Virginia; photo F.T. Campbell

  • Do you wish to strengthen efforts to develop programs that would provide long-term funding to support 1) research and development of long-term pest-control strategies such as biological control and breeding of trees resistant to insects or pathogens and 2) testing, development, and implementation of strategies to restore to the forest native tree species that have been severely depleted by non-native pests?

Then you might want to support a pair of proposed amendments that would:

  1. Establish a fund, to be managed by the National Institute of Food and Agriculture, to provide grants under which eligible institutions would carry out research intended to test and develop strategies aimed at restoring such tree species. Such strategies might include finding, testing, and deploying biological control agents or breeding of trees resistant to pests.
  2. Amend the McIntyre-Stennis Act to establish a fund to provide grants to support programs to eligible institutions to conduct experimental plantings aimed at restoring such tree species to the forest.

You can obtain copies of the proposed amendments, in legislative language, by contacting us using the “contact us” button.

Your efforts will be valuable in any case … but if your Representative or Senator is on the agriculture committee, contacting that Member will be most important!

Members of the Senate Committee on Agriculture, Nutrition, and Forestry:

Republicans (majority):

  • Pat Roberts, KS, Chairman
  • Thad Cochran, MS
  • Mitch McConnell, KY
  • John Boozman, AR
  • John Hoeven, ND
  • Joni Ernst, IA.
  • Chuck Grassley, IA
  • John Thune, SD.
  • Steve Daines, MT
  • David Perdue, GA
  • Luther Strange, AL

Democrats (minority):

Members of the House Committee on Agriculture

Republicans (majority):

Democrats (minority):


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.

Posted by Faith Campbell

Insects & Pathogens Introduced Via Plant Imports – Let’s Collaborate to Understand Risk


map showing locations in Hawaii Volcanoes National Park of ʻōhiʻa infested by rapid ʻōhiʻa death; NPS map available here

The U.S. Department of Agriculture’s adoption of a new list of plant species barred from importation pending pest risk assessment after a four-year wait (NAPPRA) [see my previous blog from June 21, here] prompts me to review what I know about pests associated with plant imports – and to appeal for collaboration among non-USDA scientists to improve our understanding of current  risks. Therefore I’m sharing some pest import and establishment data. I welcome the opportunity to work with experts to evaluate the level of risk and other matters that might be extracted from these data. Contact me to explore how we might work together.

As was pointed out by Eschen et al. 2015 (see list of sources at the end of this blog), most countries’ data on the “plants for planting” pathway are inadequate to allow an assessment of phytosanitary measures’ efficacy in preventing pest introductions. The authors stressed the need for data on:

  1. plant imports at the level of genus, including plant type and origin;
  2. pest arrival rates on each of these categories of plant imports; and
  3. pest establishments.

In the apparent absence of agencies’ efforts to close these data gaps, I propose that we work together, using available information, to improve our understanding of the current level of risk. Perhaps we can agree on which pest species are real red flags; decide which pathways most need new policy approaches; and reach conclusions about the implications of holes in the data.

  1. What Do We Know About Plant Imports?

The U.S. imports approximately 2.5 billion plants each year. The plants most likely to transport insects or pathogens that would attack North American trees and shrubs are woody plants. According to Rebecca Epanchin-Niell, during the period FY2010-FY2012, Americans imported each year more than 300 million woody plant units, belonging to about 175 genera.

Marcel Colunga-Garcia and colleagues analyzed plant import data for the period 2010-2012. They studied maritime (ship-borne) containerized plant imports, which represented 64.4 percent of the total value of all “plants for planting” imported into the U.S. in 2010, excluding imports from Mexico and Canada. The types of plants shipped in this way include rooted plants in pots; bare root plants; bulbs and tubers; root fragments, root cuttings, rootlets or rhizomes; rooted cuttings; unrooted cuttings; and budwood/graftwood.

Measuring by the plants’ import values, Colunga and colleagues determined that New York and Los Angeles metropolitan areas together import 60 percent of these plants; not all plant imports are routed through Miami – as is often assumed.

Second, these data show which states are the ultimate destination for relatively large volumes of certain types of plants. Thus, the top five states for receipt of rhododendrons and azaleas were Michigan, Oregon, California, New York, and New Jersey. Michigan received almost twice as many plants (measured by value) as New Jersey. The top three states for receipt of “fruit and nut trees and shrubs” were Florida, Louisiana, and Washington – all at nearly $1 billion or higher. California and North Carolina ranked fourth and fifth, but at values of only $200,000. It is clear from these data that contaminated plants could deliver pests virtually anywhere in the country.

Because my focus is on insects or pathogens that threaten native trees, I wish to separate those from pests that attack primarily herbaceous plants. (Of course, herbaceous plants are important components of ecosystems, as well as premier agricultural and horticultural crops! I do not mean to imply that pest threats to herbaceous plants are not important.)

About nine million of the 300 million woody plants imported to the U.S. each year belong to genera which also contain species of trees native to North America. A larger number of plants – 224 million – were in the same family as a North American native tree (Epanchin-Niell 2017). In other words, about 75% of the woody plants imported each year were in the same family as at least one species of tree native to North America.

Since plants in the same genus are more likely to transport damaging pests that would attack North American trees and shrubs, some have suggested that all such imports should be prohibited temporarily, using the NAPPRA process.

  1. What Do We Know About Pest Arrivals? (Including Detection Difficulties)

Liebhold et al. 2012, relying on 2009 data, found that about 12 percent of incoming plant shipments had symptoms of pests – a rate more than 100 times greater than that for wood packaging — a pathway that has received far more international and U.S. regulatory attention for years. This finding is similar to that of a study in New Zealand, which found that 14 percent of consignments of plants were infested – primarily with pathogens (Epanchin-Niell 2017). Worse, though, Liebhold et al. found that a high percentage of pests associated with a plant shipment is not detected by the inspectors, although APHIS has disputed this finding.


At my request, APHIS analysts compiled a list of imported woody plant genera on which pests were detected during fiscal years 2011-2016. Of the 360 quarantine pests listed, only 34 were designated as “disease” (nine percent of the total). I suspect this is significantly below the actual number entering the country.


Table 1. Overall number of pest detections recorded*

Fiscal Year # of records # of countries of origin for shipments found to be infested
2011 133 16
2012 110 14
2013 42 12
2014 27 9
2015 45 12
2016 14 5


* My totals do not include shipments from Puerto Rico; there were six pest detections on plants from the Commonwealth.

I cannot explain why the total number of detections shown in Table 1 nor – especially – the number of countries from which these infested shipments arrived fell so dramatically in FY2016. If APHIS was focused on inspecting the highest-risk shipments in FY15 and FY16, shouldn’t the number of interceptions have risen?


Pathogens are probably undercounted in Table 2 because inspectors experience great difficulty in detecting pathogens during port-of-entry inspections. For example, the genus Phytophthora does not appear in the database of port interceptions, yet we know that Phytophthora are being introduced. Also, the database does not contain the genus Rhododendron. It seems unlikely that no quarantine pests were detected on a shipment of Rhododendron over that six-year period.


Table 2. Types of Pests Intercepted

Disease                        34

Insect                           290

Mite                             20

Mollusk                       23

Nematode                    2



APHIS’s interception records are not designed as a statistically valid sample for determining the total number of pests on shipments because, for example, inspection priorities and resultant inspection criteria  change over time. Since 2015 APHIS has focused more on higher-risk shipments. Before, a specified percentage of all imports was inspected. For these reasons, interception records cannot be used to evaluate the overall risk of pests being imported along with “plants for planting” in any given year. Nor can APHIS’ interception records be compared over time.

Obviously, the numbers of pests detected on a specific type of import will reflect several factors, especially the volume of imports and the intensity of inspection. This bias in the data is reflected in the high number of pest interceptions from Central American countries – from which the U.S. imports very large volumes of plants. Two hundred twenty of the 385 pest detections recorded over the six-year period (57 percent) were on plants shipped from Costa Rica or Guatemala. Canada ranked third, with 35 pest detections (nine percent of the total).

That said, each record reflects a detection of a taxon of animal or pathogen that APHIS considers to be a “plant pest”. Each time a particular species is detected in a shipment, it is recorded. If more than one species is detected in a shipment, each species is reported separately. Therefore,

  • the number of detection records does not equal the number of shipments found to be infested;
  • the records do not reveal the number of specimens of each named taxon – either in an individual shipment or in total; and
  • the number of times a taxon appears in the database does indicate how many shipments were found to be infested by that taxon.



  1. Principal Threats to North America’s Native Trees and Shrubs

APHIS and I agree that our focus should be on those pests likely to have significant consequences if they are introduced. This risk of impact depends on climate, presence of probable hosts in the U.S., and other factors. Among the highest risk sources of imports for most the U.S. will be temperate countries, like those below. APHIS assigns a lower rating of risk to pests that are likely to be established in the U.S. already or to establish naturally – e.g., pests native to northern Mexico near the U.S. border.


Table 3. Main Temperate Countries of Origin for Infested Shipments by Year

FY2011:  Germany, Japan, Turkey, Netherlands, France, Pakistan, Canada, New Zealand

FY2012:  Israel, Canada, South Korea, China, Chile, Netherlands

FY2013:  France, Canada, Belgium, China

FY2014:  China, Canada, South Africa, Portugal

FY2015:  China, Germany, Netherlands, Canada, France, Australia

FY2016:  Canada



We can also look at the host plants on which pests are being intercepted to think about threats. Table 4 shows these. Presumably, the volume of trade in these genera, from the countries concerned, is sufficient to preclude any listing of these hosts under the NAPPRA regulatory process (see blog from June 21).


Table 4. Host Genera on which Pests Were Intercepted, Including only Genera Native

to North America or U.S. Islands or Important in Ornamental Plantings

 Plant genus                 # records — countries of origin — types of pests

Acer                             7 — primarily Canada; also Netherlands & Korea – 2 disease, 4 insect, 1 mite

Buxus                           3 – all Canada – 2 insect, 1 mollusk

Camellia                      2 – France – 1 disease, 1 mite

Chamaecyparis                        1 – Canada; mite

Cycas revoluta             8 – Honduras, Costa Rica, Dom. Rep. – insects

Fagus                          6 – Netherlands, Belgium; insects (aphids primarily)

Hibiscus                       4 – France, Tahiti, Canada – 1 disease, 1 insect, 1 mite, 1 mollusk

Ilex                              3 – Canada & NL – 2 insects, 1 disease

Liriodendron               2 – Canada – insects

Magnolia grandifolia  1 – South Africa – insect

Opuntia                       6 – Mexico – insects

Picea                           7 – Canada – insects (primarily aphids)

Thuja                           6 – Canada – insects

Tilia                             2 – Canada – mollusk


  1. What Else Do We Know?

If we look at pests introduced via all pathways, unlike those above, U.S. pest-establishment data show that plant pests continue to be introduced, but at a slower pace in recent years. In its Implementation Plan for Section 10201 of the Food, Conservation and Energy Act of 2008, USDA APHIS said that between 2001 and summer 2008, 212 pests were reported as new to the United States – an average of 30 new pest introductions each year. An APHIS database of plant pests “newly detected” during fiscal years 2009 – 2013 listed approximately 90 new taxa of plant pests as detected during this period – approximately 22 each year. In its annual report for 2016, the agency reported detecting 16 species of plant pests not previously detected in the U.S.

I think that approximately 37 of the 90 “new” pests detected over the 2009-2013 period were probably introduced via imports of plants, cuttings, or cut foliage or flowers. These include all the viruses, fungi, aphids and scales, whiteflies, and mites. I have asked APHIS to give me a database of newly detected plant pests for fiscal years 2014-2015, but the agency has not done so.

Among tree-killing pests introduced over the past 160 years, approximately 69% were introduced via the live plant trade. Liebhold et al. 2012 found that 95% of sap feeders, 89% of foliage-feeding insects, and 47% of pathogens were introduced via this pathway.

Pathogens are probably undercounted here, too, since those that do not cause massive damage are probably overlooked. Of the approximately 90 pests newly detected  2009-2013, ten were fungi, four were viruses, and two were rusts (18 percent of the total).

The genus Phytophthora does not appear in the database of “newly detected” pests. Yet we know that Phytophthora are being introduced. We know that, in 2012 a Phytophthora new to the United States — Phytophthora tentaculata — was detected on nursery-raised herbaceous plants in California. Follow-up studies have detected several additional Phytophthora taxa that might be new to the United States. One, P. quercina, had previously been reported only in Europe and Western Asia. The other putatively new taxa are still being evaluated as to whether they are previously unknown species or hybrids, and whether they are native to California or elsewhere in the United States, or are of alien origin.


The presence of the EU1 strain of Phytophthora ramorum in several nurseries in Washington, California, and most recently Oregon is also evidence that introductions of this species have continued since it was designated as a regulated pest in 2003.


Another pathogen that has apparently not been included in the official data is the fungus which causes rapid ʻōhiʻa death – a strain of Ceratocystis fimbriata. Scientists do not yet know whether this strain was introduced directly to Hawai`i on a recently-imported, asymptomatic plant; or whether the strain evolved from one or more different strains introduced to Hawaiʻi recently or longer ago.


Can you help evaluate the level of risk associated with various plant taxa, types, and origins? and other matters that might be extracted from these data. Perhaps we can agree on which pest species cause greatest concern; decide which pathways most need new policy approaches; and reach conclusions based on holes in the data. Can we use the data on pest taxa that underlie this summary – data which I have – to strengthen the case for USDA to promptly finalize revision of its “plants for planting”  (“Q-37”) regulations (see my blog from June 21 and Chapter 4 of the Fading Forests report?


Contact me to explore how we might work together.


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.




Colunga-Garcia M, Haack RA, Magarey RD, Borchert DM (2013) Understanding trade pathways to target biosecurity surveillance. In: Kriticos DJ, Venette RC (Eds) Advancing risk assessment models to address climate change, economics and uncertainty. NeoBiota 18: 103–118. doi: 10.3897/neobiota.18.4019


Epanchin-Niel, R.S. 2017. Presentation to 28th USDA Interagency Research Forum on Invasive Species. January 2017.


Eschen, R., K. Britton, E. Brockerhoff, T. Burgess, V. Dalley, R.S. Epanchin-Niell, K. Gupta, G. Hardy, Y. Huang, M. Kenis, E. Kimani, H.-M. Li, S. Olsen, R. Ormrod, W. Otieno, C. Sadof, E. Tadeau, M. Theyse. 2015. International variation in phytosanitary legislation and regulations governing importation of plants for planting. Environmental Science and Policy 51 (2015) 228-237

Liebhold, A.M., E.G. Brockerhoff, L.J. Garrett, J.L. Parke, and K.O. Britton. 2012. Live Plant Imports: the Major Pathway for Forest Insect and Pathogen Invasions of the US. www.frontiersinecology.org



Surprise! USDA Through APHIS moves on NAPPRA regulations


USDA headquarters; F.T. Campbell

To my complete surprise, USDA APHIS has finalized a four-year-old proposal to temporarily prohibit importation of 56 taxa of plants: 22 that are likely to be invasive and 34 that are hosts of eight insects, pathogens, or other types of plant pests.

On June 19, APHIS published a notice in the Federal Register announcing that APHIS had finally acted on a proposal initially published on May 6, 2013. To view the datasheets APHIS prepared and the comments APHIS received, go here.

Under APHIS’ regulations in ‘‘Subpart— P4P’’ (7 CFR 319.37 through 319.37–14 …), APHIS prohibits or restricts the importation of “plants for planting” – living plants, plant parts, seeds, and plant cuttings – to prevent the introduction of “quarantine pests” into the US. A “quarantine pest” is defined in § 319.37–1 as a plant pest or noxious weed that is of potential economic importance to the United States and not yet present in the country, or is present but is not widely distributed and is being officially controlled.

Section 319.37–2a authorizes APHIS to identify those plant taxa whose importation is not authorized pending pest risk analysis (NAPPRA) in order to prevent their introduction into the United States. As regards plant taxa that have been determined to be probable invasive species, such importation is restricted from all countries and regions. For taxa that have been determined to be hosts of a plant pest, the list includes (1) names of the taxa, (2) the foreign places from which the taxa’s importation is not authorized, and (3) the quarantine pests of concern.

The plant taxa now regulated because they host various types of plant pests are listed in two parts.

1) Species designated during the first round of action were proposed in 2011 and finalized in 2013 =


2)  Species proposed in 2013 and finally designated on June 19, 2017 =



In summary, the second round of NAPPRA seeks to prevent introduction of the following specific pests by prohibiting imports of their associated plants from most countries. Imports from Canada are often excepted and those from the Netherlands less often.

  • Asian longhorned beetle (ALB, Anoplophora glabripennis) – Celtis, Cercidiphyllum (katsura), Koelreuteria, Tilia
  • Great spruce bark beetle (Dendroctonus micans) – Pseudotsuga
  • Japanese pine sawyer (Monochamus alternatus) – Cedrus
  • Phytophthora kernoviae 17 genera, including Camellia, Fagus, Hedera, Ilex, Leucothoe, Liriodendron, Magnolia, Pieris, Quercus, Rhododendron, Sequoia, Vaccinium
  • Boxwood blight (Puccinia buxi) – Buxus (boxwood)


There are other restrictions on plant imports related to pests, which predate the most recent NAPPRA listing. These include =

  • Acer is already listed on the previous NAPPRA list for all countries except Canada, Netherlands, and New Zealand.
  • Longstanding regulations prohibit the importation of Abies species from all countries except Canada. The genera Larix, Picea, and Pinus were added to the NAPPRA list in the April 2013 NAPPRA notice.
  • Camellia was also listed in 2013 from all countries, except Canada, to prevent introduction of the citrus longhorned beetle (CLB, Anoplophora chinensis); the genus is also regulated for Phytophthora ramorum. The most recent action now adds restrictions because Camellia is also a host of Phytopththora kernoviae. Plants from Canada are exempt because of longstanding “significant trade” volumes.
  • While plants in the genus Cercidiphyllum (katsura) may be imported from the Netherlands – despite the presence in the country of both ALB and CLB – a 2013 Federal Order (DA–2013–18) specifies mitigation actions which exporting countries must take to prevent transport of these insects via trade in this or other genera.
  • Hedera was added to the NAPPRA list via the first round of proposals in April 2013 as a host of CLB. Under the 2013 proposal, the genus is also listed as host of Phytophthora kernoviae.
  • Vaccinium are consistently exported only from Canada and Australia. The genus is listed because it is a host of Phytophthora kernoviae.

As APHIS notes in its explanation in the Federal Register, P. kernoviae has been reported in England, Ireland, and New Zealand; APHIS considers this to be evidence of spread of the pathogen through the global movement of plants. APHIS notes further that the pathogen has a large number of confirmed hosts and there is currently no effective control measure. APHIS does not note that the native range of P. kernoviae is unknown.

APHIS received considerable pushback on its proposal to restrict importation of Callistephus, Chrysanthemum, and Eustoma spp. to prevent introduction of several pathogens, including chrysanthemum stem necrosis virus (CSNV) and chrysanthemum white rust.  In response, APHIS has withdrawn these three genera from the new NAPPRA listing while it conducts a commodity import evaluation document (CIED) for Chrysanthemum.


I have not discussed here NAPPRA as it applies to invasive plants. In April I blogged about the need for APHIS to act. Plants listed because of their invasive potential are posted here =

1) 2013 listing: https://www.aphis.usda.gov/import_export/plants/plant_imports/Q37/nappra/downloads/QuarantinePestPlants.pdf

2) 2017 listing: https://www.aphis.usda.gov/import_export/plants/plant_imports/Q37/nappra/downloads/quarantine-pest-plants-round2.pdf

Again, I welcome USDA’s finalization of this second round of regulations and look forward to new proposals.


History of NAPPRA

In December 2004 APHIS published in the Federal Register an Advance Notice of Proposed Rulemaking, or ANPR which outlined a strategy for reducing pest introductions via the “plants for planting” pathway. The strategy had two major steps.

First, the agency would create a temporary holding category for plants suspected of transporting insects or diseases. This would allow APHIS to suspend imports of particular plants, from certain countries, until a full risk assessment was completed.

Second, APHIS would issue regulations establishing a general framework to minimize the presence of pests. Using this, the agency would negotiate country-specific requirements for imported plants, working toward an approach that would rely on “integrated measures” (also called “integrated pest management”).

APHIS formally proposed to create the temporary holding category – the NAPPRA program – in 2009. The regulations were finalized in May 2011 – six and one half years after the intention to take this action was announced in the ANPR. In adopting the NAPPRA rule, APHIS reiterated the need to encourage, but not require, the plant import trade either to rely on low-risk plant materials or to adopt pest-reduction methods.

In July 2011, APHIS published the initial list of species proposed for inclusion in the NAPPRA category.  This list was finalized in April 2013. A second list of species proposed for NAPPRA listing was published in May 2013.

This history – with citations – can be found in chapter 4, “Invasion Pathways”, in my report Fading Forests III, available here.


Meanwhile, here are a few related FAQs about NAPPRA as it is being implemented.


Why does APHIS regulate by genus?

APHIS regulates pests’ hosts at the genus level because when a new species is identified as a host, additional scientific studies often identify other host species within that genus. Therefore, regulating all species within the genus is the preferred course of action until a formal Pest Risk Analysis (PRA) is conducted. Uncertainties are worked out then.


How do these new rules fit into international standards?

APHIS notes in the Federal Register notice that  the “plants for planting” pathway is recognized as posing a high risk  for the introduction of pests. For this reason, the International Plant Protection Convention recommends that countries require a pest risk analysis before allowing importation of a plant taxon from a new country or region.


How long is importation of plants prohibited?

NAPPRA listing does not prohibit the importation of taxa indefinitely. Imports are held up until a pest risk analysis can be conducted to identify appropriate mitigation measures. Furthermore, an importer may apply for a controlled import permit to import small quantities of a prohibited or restricted taxon for developmental purposes.


What is the meaning of “significant trade”?


If a taxon that is a host of a quarantine pest has been imported in ‘‘significant’’ quantities from a specific exporting country, it is not eligible for the NAPPRA prohibition. Currently APHIS defines “significant trade” as the importation of 10 or more plants of a taxon in each of the previous three fiscal years. At the urging of one commenter, APHIS is considering whether to alter that definition by looking at import volumes over three out of five years – although the agency said if it took that action, it would most likely also consider raising the base number of plants from 10 to a higher level.


In the case of “significant trade” in a taxon that is a host of a quarantine pest, APHIS specifies other measures to address the pest risk.


What other protections does APHIS use?

A “Federal order” is used to rapidly take action to prevent the introduction of a quarantine pest, and is generally followed by notice and an opportunity for public comment. This is a separate action from the NAPPRA process.




The Overhaul of Regulations for “Plants for Planting (P4P) (the “Quarantine-37” or “Q-37” regulations) – Will It Also Be Finalized?


Another important APHIS action aimed at improving control over introductions of pests on imported plants has also been unresolved for four years. This is the revision to the agency’s overall plant import regulations, which was also proposed in May 2013. The revision would restructure the current regulations by moving specific restrictions on the importation of taxa from regulations to the Plants for Planting Manual. That transfer would allow specific restrictions to be changed without going through the full public notice and comment process required for amending formal federal regulations. The proposed revision would also add a framework for requiring foreign plant suppliers to implement integrated pest management measures to reduce pest risk. Experts believe that depending on integrated measures will better prevent pest introductions than the current reliance on a visual inspection at the time plants are shipped.


Again, for a history of and rationale for the proposed regulatory change, read chapter 4, “Invasion Pathways”, in my report Fading Forests III, available here.


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.


Status of Phytopthoras in the United States & Europe: an update

tanoak killed by sudden oak death; Marin County, Calif. photo F.T. Campbell

Here is some interesting information from recent issues of the the California Oak Mortality Task Force’s bimonthly newsletter. I am updating my earlier blogs on the status of Phytophthoras and sudden oak death (SOD) in the United States and Europe.


More than 600 samples were taken from streams or ponds in nine states (Alabama, Florida, Georgia, Mississippi, North Carolina, Pennsylvania, South Carolina, Tennessee, and Texas) during 2016. Ten of the samples were positive: seven from three streams in Alabama and three from one stream in Mississippi. Each of these had tested positive before; none was a new positive location. [March newsletter]


  • The disease continues to spread in Oregon and California:

During 2016 and early 2017, sudden oak death and tanoak mortality continued to intensify within the officially designated quarantine zone in southwest Oregon. So far, no new outbreaks have been detected outside the quarantine zone.

In Oregon, there is growing concern about the disease and the paucity of funds to address it. As a result, Oregon state Representative David Brock Smith and U.S. Senator Jeff Merkley have formed an Oregon Sudden Oak Death Task Force. The Task Force is developing a collaborative action plan to secure enough funding to contain the infestations of the NA1 genetic strain (the one widespread in Oregon and California) and to eradicate the EU1 lineage (this is the only known site where this strain is established in the forest in North America; see my blog from August 2015, which explains the significance of these strains.)  [March newsletter]


In California, scientists have been surprised by the intensity of the disease in several parks on the eastern side of San Francisco Bay – an area that is drier than most forests that are infested. The severe drought of recent years has not prevented spread of the disease. Even more surprising, one park has very little California bay laurel – which is considered to be the primary source of infection. [March newsletter]


  • Native plant nurseries may be spreading various Phytophthoras (see my blog from last year here) or the presentations on “Phytophthora Detections in Native Plant Nurseries and Restoration Sites” posted here)

The National Ornamentals Research Site at Dominican University (NORS-DUC) sampled several types of native plant nurseries in fall 2016 to determine the extent of movement of Phytophthora species on plants they sell. Unfortunately, the report in the newsletter did not include results of the sampling. [January 2017]

CFDA photo of herbaceous plants with Phytophthora infection

Oregon and Washington authorities acted in response to the initial reports from the San Francisco area, and sampled nurseries in their states. They found a similarly high infestation rate in native plant nurseries in their states. Washington State University and Oregon State University have held several 2 ½-day workshops on “Preventing Phytophthora Contamination in Native Plant Nurseries and Restoration Sites”. [May newsletter]

For more information about Phytophthoras in native herbaceous plants in California, visit http://ucanr.edu/sites/sod6/Proceedings/Presentations_and_Posters/  and  www.calphytos.org

  • Disease costs in England and Wales could top 1 billion dollars


Drake and Jones have estimated that damage by Phytophthora ramorum and P. kernoviae [link to Gallery] to non-extractive public use and non-use values at risk from uncontrolled spread of these diseases in England and Wales is £1.446 billion per year (approximately $US 1.82 billion). The greatest public value at risk (slightly more than one-third) is from an uncontrolled spread of these diseases to heritage gardens; lower risks are to the diseases’ spread to woodlands and heathlands. [March newsletter]


5) Ireland resembles Europe in numbers of Phytophthora species:


O’Hanlan and colleagues tested more than 11,000 samples from both “trade” environments (presumably, nurseries) and “non-trade” environments (presumably plantings or natural environments). They detected 19 species and 3 informally designated taxa of Phytophthora, including 8 new records for Ireland. Thus, Ireland’s situation is similar to that in Europe more broadly – a study last year by Junker and colleagues report the detection of 15 Phytophthora species in two commercial woody ornamental nurseries [link to blog about Phythophs in Europe] In Ireloand, P. ramorum was found on 30 hosts; P. syringae on 6 hosts; P. kernoviae on 3 hosts. Phytophthora species were most frequently detected on rhododendrons – (12 Phytophthora species). [January newsletter]




Drake, B. and Jones, G. 2017. Public Value at Risk from Phytophthora ramorum and Phytophthora kernoviae Spread in England and Wales. Journal of Environmental Management. 191: 136–144.


Junker, C., Goff, P., Wagner, S., and Werres, S. 2016. Occurrence of Phytophthora in commercial nursery production. Plant Health Progress. 17:64-75.


O’Hanlon, R.; Choiseul, J.; Corrigan, M.; Catarame, T.; and Destefanis, M. 2016. Diversity and Detections of Phytophthora Species from Trade and Non-Trade Environments in Ireland. EPPO Bull. 46: 594–602. DOI: 10.1111/epp.12331.



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.


Lobby House and Senate Agriculture Appropriations Subcommittees in support of increasing funding for two crucial APHIS programs


On May 19 I posted a blog asking you to lobby Congress in support of maintaining current funding levels for two programs aimed to eradicating or containing tree-killing pests.  These are the “tree and wood pest” and “specialty crop” programs operated by the USDA Animal and Plant Health Inspection Service (APHIS).

At the time, I had not seen the President’s budget proposal. Now I have seen the President’s budget – and, as anticipated, it calls for steep cuts in the “tree and wood pest” program. The President calls for cutting this program by 44% — from $54 million to $30 million. Specifically, the Asian longhorned beetle (ALB) eradication program would be cut by approximately 50% — $20.770. The emerald ash borer (EAB) containment program would also be cut by half — $3.127 million.

The President’s budget justifies these severe cuts by saying that states, localities, and industries benefit from eradication or containment of the ALB and EAB, so they should help pay for the containment program.  The Office of Management and Budget states that other beneficiaries should pay 50% of program costs.

For whatever reason, the budget does not propose to cut APHIS’ efforts to prevent spread of the European gypsy moth.

In reality, states, localities, and industries are very unlikely to make up the difference in funding. We should remind the Congress that already, local governments across the country are spending more than $3 billion each year to remove trees on city property killed by non-native pests. Homeowners are spending $1 billion to remove and replace trees on their properties and are absorbing an additional $1.5 billion in reduced property values and reducing the quality of their neighborhoods. (See Aukema et al. article listed below.)

ash tree killed by EAB; Ann Arbor, MI; courtesy of Major Hefje


Cuts of the size proposed by the President’s budget will undermine the programs completely. Such a result is particularly alarming given the record of success in eradicating ALB populations – when resources are sufficient; and the urgent need to complete eradication programs in Massachusetts, New York, and Ohio. As I said in May, the ALB program has succeeded in eradicating 85% of the infestation in New York. (APHIS has just announced that a section of the borough of Queens is free of ALB.) However, the infestation in Massachusetts has been only 34% eradicated; that in Ohio has been only 15% eradicated. Crippling the program now will expose urban and rural forests throughout the Northeast to severe damage by this insect, which attacks a wide range of species.

The importance of continuing the EAB containment program has been re-emphasized by scientists’ recent determination that EAB can attack commercial olive trees as well as all species of ash.

The budget also does not recognize the need for APHIS to expand its program to address other tree-killing pests, including the spotted lanternfly, and polyphagous and Kuroshio shot hole borers.The shot hole borers attack hundreds of tree species, including California sycamore, cottonwoods, and several oaks. Many known hosts are either found across the Southeast, or belong to genera that are found across the Southeast – so the threat is national. The spotted lanternfly – now established in Pennsylvania — threatens agriculture – especially grapes, apples, plums, cherries, peaches, nectarines, apricots, and almonds; as well as oak, walnut, poplar, and pine trees.

More than 30 tree-attacking pests have been introduced in recent years. Additional species from these introductions might also require APHIS-led programs; one example is the velvet longhorned beetle.

velvet longhorned beetle; bugwood.org

The budget calls also for a 6% cut on the “specialty crops” program – from $158 million to $148 million.  It is not clear how such a reduction would affect APHIS’ program to prevent spread of the sudden oak death (SOD) via movement of nursery stock [link to earlier blogs & Gallery]. The SOD program has been funded at approximately $5 million in recent years.

Finally, additional challenges lie ahead because it is likely that new tree-killing pests will be introduced with rising import volumes. Each year, border inspectors detect more than 800 import shipments with pests infesting the crates and pallets. These represent a small proportion of the actual risk; one analysis estimated that 13,000 shipments with infested packaging enter the country each year. APHIS must have sufficient resources to respond when the inevitable newly introduced pests are detected.

CBP agriculture specialists in Laredo, Texas, examine a wooden pallet for signs of insect infestation. [Note presence of an apparent ISPM stamp on the side of the pallet] Photo by Rick Pauza

Aukema, J.E., B. Leung, K. Kovacs, C. Chivers, K. O. Britton, J. Englin, S.J. Frankel, R. G. Haight, T. P. Holmes, A. Liebhold, D.G. McCullough, B. Von Holle.. 2011. Economic Impacts of Non-Native Forest Insects in the Continental United States PLoS One September 2011 (Volume 6 Issue 9)

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.

Plan to Join the Continental Dialogue in Savannah, Georgia, in November 2017!

Spread of laurel wilt since 2003; source: USFS

Redbay mortality, Claxton, GA 2009

photo by Scott Cameron

The southeastern states have been invaded by a smaller number of non-native, tree-killing insects and pathogens than some other regions (see map below). But among these are highly damaging pests that show just how vulnerable this area’s native species and forests are, e.g., chestnut blight, laurel wilt, hemlock woolly adelgid, balsam woolly adelgid, and now emerald ash borer (all described here).

Join the Continental Dialogue on Non-Native Forest Insects and Diseases at its annual meeting in Savannah, GA, November 9 & 10, 2017 to learn about the issues outlined below and to build relationships to sustain action. The meeting will be in conjunction with the Annual Gypsy Moth Review, so we will also discuss the most recent developments pertaining to European and Asian gypsy moths. Visit www.continentalforestdialogue.org to see the agenda and registration information (both to be posted soon).

The Southeast is at high risk for greater damage because:

  • The Port of Savannah is already the largest container port on the East Coast. Now, it moves 20,000 shipping containers per day and it is adding infrastructure to increase this volume.

Most of these containers – and their accompanying wood packaging material (for more on the risk from wood packaging, see my blog from the end of January; and fact sheets here) quickly move to distribution centers or their ultimate destinations – throughout the Southeast but as far away as Chicago. However, the port has storage for millions of containers on paved container yards that total 1,200 acres.  The storage yards are close to mixed forests.

Trees across road from stored containers at Port of Savannah;  photo by F.T. Campbell

More of these ships and containers will come directly from Asia – the major source of our most damaging invaders — now that the Panama Canal has been widened. When I visited the port in mid-May, the largest container ship ever to visit the U.S. East Coast was being unloaded – and re-loaded simultaneously!  The “Cosco Development” carries 13,200 TEUs (twenty-foot equivalent containers).

Unloading “Cosco Development” at Port of Savannah; photo F.T. Campbell

  • The sudden oak death pathogen (Phytophthora ramorum) has been found in streams and ponds in several southeastern states – Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, and Texas. Positive samples were drawn from three streams in Alabama and one stream in Mississippi in 2016. Most of these water bodies are near nurseries that had received infested plants from West Coast suppliers. In addition, infested plants have been detected recently in nurseries or landscape plantings in Louisiana, Texas, and Virginia, as well as in other states farther north [link to 2015 blog]. These infested plants have been removed. What is the current scientific thinking about the implications of these detections? Last I heard, scientists thought the pathogen cannot survive in water; it needs some plant material. Yet scientists have not found on-going infestations on plants along the streams and ponds. For more information on SOD, visit http://www.suddenoakdeath.org/


  • Over recent decades, a half dozen non-native insects that attack pine trees have become established in the continental United States. These include the Sirex woodwasp, common pine shoot beetle, golden (or red) haired pine bark beetle (Hylurgus ligniperda), Mediterranean pine shoot beetle (Orthotomicus erosus) — all described here. The mountain pine beetle (Dendroctonus ponderosae) has spread east of the Rocky Mountains and might eventually reach pine forests of the Midwest and East.


While none of these (other than the mountain pine beetle) has yet caused very much damage where they are established, should we continue to assume that they will not cause damage once they reach the “pine basket” of the Southeast? Even if plantations can be managed to minimize risk, what are the implications for natural pine forests so important to the ecosystems and protected areas of the region?


It is unclear whether the fact that the Secretary of Agriculture, Sonny Perdue, is a former governor of Georgia with a record of support for forestry will raise attention to some of these issues.  As you might remember (see my blog from March 28th), apparently no senators raised invasive pest issues during Secretary Perdue’s confirmation.

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.