Category: invasive species

Invasive species on the African Continent

We are beginning to get more information about invasive species on the African continent.

a flyer naming principal invasive ornamental plants in Kruger National Park

In several countries, the focus has been on threats to agriculture. Previous blog about horizon-scanning in Ghana. In Zimbabwe, N. Mudada and colleagues (2026; full citation and the end of this blog) found alarming, if not surprising, levels of risk to food production from introduced invasive plants. They investigated 1,668 human-aided transboundary plant introductions at 14 ports of entry and non-official crossing points over the course of four years.

They estimate that the 20,000 trucks that transported maize into the country over the four years carried over 20,700 metric tons of weed seeds and rubbish! They recorded detections of 11 species in eight orders. The pathways are familiar. As noted, several weeds were contaminants of grain shipments; Convolvulus arvensis in wheat for human consumption, Helianthus annus and Datura stramonium in maize for animal feed. Adenium obesum and Vitex agnus-castus were being smuggled for planting as flowers and ornamentals. (Vitex agnus-castus was also smuggled in passenger baggage for its medicinal properties). Several Lemna species (an aquatic plant) were also smuggled for planting as animal feeds.

In some cases, the focus is the threat to native ecosystems. I posted a blog the about threat of an introduced pathogen to trees in the remnant rain forests of Madagascar.

South Africa still has the lead in addressing invasive species. Regarding invasive plants specifically, the country has the benefit of more than 150 years of botanizing. The richness of the region’s flora is globally recognized. South Africa also has a long history of studying and managing invasive species, especially plants.

South African scientists and colleagues in Botswana, Eswatini, Lesotho, and Namibia have published four editions of the Flora of the Southern Africa region since 1984. In 2006, the PRECIS database of the South African National Biological Diversity Institute (SANBI) was combined with the Tropical African Plant Checklist published by the Conservatory and Botanical Garden of Geneva to create the African Plant Checklist and Database Project. It is continually updated. This is the first continental flora checklist for Africa; it fulfils countries’ obligations under the Convention on Biological Diversity’s Global Strategy for Plant Conservation.

For South Africa specifically, scientists have produced a national plant checklist that is updated annually.

The 2025 Checklist reports that 21,539 plant species are extant outside cultivation in the country; these comprise 20,204 indigenous species and 1,329 naturalized species. Thus, 6% of the total flora is non-indigenous. Of these, 649 (48.8% of the non-indigenous species, 3% of all plants) of them are invasive.

[Naturalized species are defined as species whose documented natural range does not include South Africa, but have overcome a biogeographic barrier and now sustain self-replacing populations for two or more life cycles or over a given period of time in the country. These populations are maintained without direct intervention by people, or despite human intervention. Invasive species meet the above definition plus produce reproductive offspring, often in large #s at considerable distances from the parent and/or site of introduction, and have the potential to spread over long distances.]

Since the previous checklist was published in 2006, botanists have identified 1,048 additional species – a 4.9% increase. Eighty-two percent of the newly identified species (865 species) are “naturalized”. Specifically, 414 new species are categorized as naturalized (a 31.1% increase), and 451 new species are classified as invasive (a whopping 69.5% increase). Le Roux and Klopper attribute these steep increases to active botanizing by SANBI’s Invasive Species Programme (begun in 2008), and the Southern African Plant Invaders Atlas Project (begun in 2010).

Of the 384 plant families present in South Africa, 350 contain at least some indigenous species. Thirty-four families contain only naturalized species. Among the 2,189 plant genera present, 459 (21%) contain only species that are non-indigenous.

Three families stand out because of the particularly high numbers of naturalized species: Fabaceae (143 species; 11% of all naturalized species), Asteraceae (140 species; 10%), Poaceae (123 species; 9%). Two of these families — Asteraceae and Fabaceae — are also the largest families among native South African plants. The third, grasses (Poaceae), ranks seventh in the list of most specious families indigenous to South Africa. The next group of families with high numbers of naturalized species has less than half as many invasive species: Myrtacae (55), Amaranthacea (52), Solanaceae (48). None of these families ranked within the top 20 families of indigenous plant species.

The genera with the most naturalized species were Solanum, Euphorbia and Acacia (all 24 or 23 species).

Acacia cyclops; photo by David M. Richardson

South African scientists are also exploring how to balance conflicting goals and perspectives when an invasive plant species has economic or social value. The example chosen by Mbobo et al. (2025) is guava (Psidium guajava) – a nutritious and popular tropical fruit grown commercially in South Africa, but also invasive along roadsides, watercourses and forest margins. Invasions are especially common in eastern parts of country; large monocultures are found in KwaZulu-Natal. Outbreaks have also been detected at five sites in Western Cape in riparian zones and at a hot spring. Mbobo et al. (2025) note that the microclimatic conditions at this last location differ from the broader conditions in the region – which are what most models would measure.

The scientists used models to predict where guava might invade – especially in large monocultures – and compared those areas to where the tree can be grown in cultivation with human inputs, e.g., irrigation. They then assessed whether six regulatory approaches would avoid restricting guava farming in areas at minimal or low risk while still protecting vulnerable locations. They also considered the amount of information required to implement the approach and costs of acquiring the information; and level of likely public acceptance. Mbobo et al. (2025) laid out the trade-offs between continuing to regulate planting of the species at the provincial level vs. at the municipal level. Prohibiting planting of guava in provinces where it is recorded as invasive allows some plantings near natural forests and riparian areas that are highly susceptible to guava invasions. On the other hand, nearly half of the prohibited area is outside the known or likely at-risk area. The provinces do allow exceptions through a permit process. Adopting more geographically limited rules by regulating at the municipal level would enable a tighter link to geographic areas at highest risk. However, this approach does not address long-distance seed dispersal by animals. Furthermore, the very detailed regulations might confuse stakeholders and complicate enforcement. Also, the models lack sufficiently fine spatial resolutions to predict invasible areas so accurately. Finally, the reduction in regulated area is minimal (~ 14%), so the economic benefits are unlikely to outweigh the significantly higher administrative costs and risk of allowing guava invasions in new sites.

Guava fruit on tree; Roenashy via Wikimedia

Gildenhuys et al. (2026) analyzed the factors that drive which non-native plants establish where. They assessed the roles of temperature, precipitation, urbanization intensity, urban area, travel time, year of city’s establishment, and human population density in determining which plant species are present in 54 urban centers in Western Cape Province. The cities have significant differences in climate: Mediterranean in the far southwest, warm temperate in the southeast, and semi-arid towards the interior. The expectation was that these drivers and assembly processes are influential at more advanced invasion stages when the species have already overcome some barriers to dispersal, so are now found in reasonably suitable habitats.

Gildenhuys et al. (2026) found temperature and precipitation were most important in determining plant species’ presence. This was especially true at the boundary between arid and mesic climates. These strong environmental gradients are the same ones which have driven high differences in native species presence across the province. [See pamphlet describing invasive plants in Cape Town.] This finding supports the “Goldilocks hypothesis”: that non-native plant species assemblages are driven by the same abiotic variables as native species assemblages. While did not directly study the “Biome decides hypothesis” (the composition of non-native flora is mediated by the biotic effects of native flora and fauna), Gildenhuys et al. (2026) doubt its applicability here because native species’ presence has probably been greatly reduced by the effects of urbanization.

Urbanisation intensity itself ranked third as a factor. Its effect was strongest at low to medium urbanization intensities. Because urbanization creates novel habitats, such as, “hardscapes” of paved surfaces that resemble deserts, their non-native plant assemblages are dominated by similar, urban specialist, species. At lower urbanization intensities a greater variety of habitats is available. Gildenhuys et al. (2026) conclude that urbanization acts primarily as a driver of opportunistic habitats for species at later invasion stages rather than as a filter of species introduction.

An earlier study found a similar effect from road density (often associated w/ urbanization) as an explanation for where specific woody non-native species establish. They do concede that larger urban areas might experience greater propagule pressure.

Gildenhuys et al. (2026) note that recent globalization of the plant trade has probably changed the specis planted in urban centers. For example, cities in the Western Cape are increasingly replacing English oak (Quercus robur) with more disease-resistant oaks. The change might reflect greater environmental awareness and regulations issued under the National Environmental Management: Biodiversity Act 10 of 2004. In newly established urban centers, fewer invasive species are being planted — at least among trees.

SOURCES

Gildenhuys, C.P., L.J. Potgieter, C. Hui, D.M. Richardson. 2026. Drivers of compositional turnover of the NIS urban flora in the W Cape, South Africa. Urban Ecosystems (2026) 29:51 https://doi.org/10.1007/s11252-026-01919-3

Le Roux, M.M., R.R. Klopper. 2025. Taking stock of South Africa’s flora. South African Journal of Botany 184 (2025) 571-579

Mbobo, T., D.M. Richardson, A. Datta, K.T. Faulkner, J.R.U. 2025. Wilson. Spatially-Differentiated Reg of NIS Can Be Improved Using Spp Distribution Models: Psidium guajava in South Africa as a Case Study. Diversity and Distributions. 2025 31:e70102 https://doi.org/10.1111/ddi.70102

Mudada, N., J. Chitamba, E. Nyangani, C. Chapano, N. Mapope,and W. Ngezimana. 2026. Weeds associated with cross border traffic, their approach and infestation rates in Zimbabwe.  ISABB Journal of Food and Agricultural Sciences. Vol. 12(1) January-June 2026. DOI: 10.5897/ISABB-JFAS2025.0192

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

Or

https://fadingforests.org

Factoids from recent publications

Agrilus auroguttatus

Agrilus genus

Hernández‐Gutiérrez, Nichols, and Kelly (2026) (full citation at the end of the blog) analyzed interactions between this genus of beetles and oaks (Quercus species). In this context, they report that 32 Agrilus species from Africa, Asia, Europe, and North and South America use 51 Quercus species as hosts in their native range. Eighteen (56.25%) use only Quercus hosts.

Oaks that host Agrilus species cluster in several clades, i.e., the entire Section Cerris and one clade of Section Ilex and two clades of section Lobatae. Clades where Agrilus hosts are underrepresented are Sections Cyclobalanopsis and Quercus &, surprisingly, two clades in Section Lobatae.  

Their analysis indicated that beetle-oak interactions involving all the 32 Agrilus species and 105 Quercus species in their study had a significant likelihood of being damaging. For example, northern red oak (Q. rubra) is already known to host six Agrilus species. Hernández‐Gutiérrez, Nichols, and Kelly (2026)’s analysis indicated that this tree species might be utilized by all 32 Agrilus species assessed. The tree’s wide distribution (both native and introduced) places it close to other known or probable hosts, which exacerbates the risk of an interaction. Another 26 Quercus species are predicted to host ten or more Agrilus species.

The model was not successful in predicting hosts of A. auroguttatus (goldspotted oakborer) in its introduced range in California.

black oak (Quercus kelloggii) in Cleveland National Forest killed by GSOB; photo by F.T. Campbell

It also predicted that few of China’s oak species might host Agrilus beetles. However, as Dr. Robert Haack notes (pers. comm. June 2026), larval hosts have been identified for only 13% of the nearly 1,200 Asian Agrilus.

Some Agrilus species have a very large number of predicted novel interactions. A. graminis and A. angustulus are predicted to have more than 40 novel oak hosts. Both have numerous known oak hosts; so their “polyphagous” nature is already documented.

Since two-thirds of 666 Agrilus species with known larval hosts exploit only one plant genus as a host in their native range, Hernández‐Gutiérrez, Nichols, and Kelly (2026) assert that they might spread faster if introduced to homogeneous rather than species-rich habitats. Dr. Haack believes that this statement is too broad (pers. comm. June 2026).

A. bilineatus; photo by Christina Butler via Wikimedia

Twolined chestnut borer

Haack and Blank (2024) document that the twolined chestnut borer, Agrilus bilineatus has preferentially infested apparently healthy English oak (Quercus robur) trees over healthy native oak trees in Michigan. In North America, A. bilineatus is a major pest of oaks and American chestnut (Castanea dentata)when they are stressed by drought or other factors. Infestation typically begins in the upper crown and proceeds downward; tree death often occurs within three years.

 At several sites in southern Michigan, where English oaks were intermixed with native white oaks (Quercus alba) and close to northern red oaks (Quercus rubra), A. bilineatus preferentially infested Q. robur trees that initially appeared healthy. Further study revealed that many of the English oaks attacked had low or depleted root starch levels.

Although these findings are cause for alarm, English oak is already used by 11 species of Agrilus in Europe. Perhaps the tree and ecosystem might have sufficient defenses in Europe. Meanwhile, A. bilineatus has been reported in Turkey as of 2018; I have found no recent information about the damage whether it is causing any damage there.

Data from Britain and Worldwide

Peyton et al. (2026) reviewed the effectiveness of a “horizon scanning” exercise conducted for Great Britain (England, Scotland and Wales). They report that 3,248 recognized non-native species have been detected in Great Britain, of which 2,016 have established self-sustaining populations. Some 194 (~10%) are considered invasive, that is, have negative impacts on biodiversity and wider ecosystem viability. These consist of 108 terrestrial species, 47 freshwater species, and 39 marine species. These bioinvaders cost the British economy an estimated ~£3.9 billion per year (the bulk of the damage is attributed to ash dieback, caused by the fungus Hymenoscyphus fraxineus).

In the decade between completion of the “horizon scan” and the present, 143 species were recorded as being introduced. The horizon scan predicted 31 of these species, 22%. Peyton et al. (2026) consider this to be success.

Peyton et al. (2026) report that globally, ~ 6% of non-native plant species are ranked as invasive. Among invertebrates, this proportion rises to 22%. Considering vertebrates introduced to Europe or North America, the figure is more than 50%!! I welcome global data that support my call for rethinking the “rule of tens” long relied on for estimating the proportion of non-native species that are invasive.  

Discussing bioinvaders’ role in causing extinctions, Peyton et al. (2026) report that 30 predators have been linked to declines and extinctions of 738 vertebrate species.

Peyton et al. (2026) also discuss the difficulty in predicting an introduced species’ impacts when in some cases the time lag between introduction and presence in the wild or between establishment and spread w/in the region can last decades or even a century. They cite as an example Senecio squalidus, which escaped the Oxford Botanic Gardens in the 1700s but started to spread only during mid-1900s.

Australia

More than 300 non-native insect pests, pathogens and nematodes have established on tree or shrub hosts in Australia; 20% have caused moderate to high impacts to commercial plantations, urban forests, or trees in natural ecosystems (Carnegie et al. 2026).The rate at which non-native forest pests and pathogens have been detected in Australia has doubled since 2018 compared to earlier decades: from ~ 1.5 to ~ 3 per year. Carnegie et al. (2026) attribute this rise to greatly expanded official surveillance efforts. Still, three-quarters of the most recent detections came too late for eradication to be attempted.

The Forestwatch program (inaugurated – under a different name – in 2022) includes pathogens. I rejoice!!! Still, the target species threaten primarily tree species not native to Australia but important to commercial forestry or urban forests: Asian longhorned beetle,  burnt pine longicorn (Arhopalus ferus), pine pitch canker, pine wilt disease, red turpentine beetle (Dendroctonus valens), Asian spongy moth, red needle cast, and sudden oak death. The exceptions are strains of Austropuccinia psidii not yet intro to Australia, and eucalypt leaf blight (caused by Teratosphaeria destructans) (Carnegie et al. 2026).

Austropuccinia psidii infection on Melaleuca in Australia; photo by John Tann via Flickr

Among the introduced pests causing the greatest damage to native species are

  • Phytophthora cinnamomi: this soil fungus can kill 40% of the plant species in the southern portion of Western Australia  – which is one of 36 “Biodiversity Hotspots” recognized by the Critical Ecosystem Partnership Fund.  
  • Austropuccinia psidii (cause of myrtle rust) in natural ecosystems; Members of the host family Myrtaceae occur in 11 of 13 major vegetation formations on Australia. Various authorities have identified 76 species as at risk to the rust.

I hope the Australians are developing strategies for landowners to counter damage by the polyphagous shot hole borer (Euwallacea fornicatus) and its associated fungus (Fusarium euwallaceae). DMF Outbreak detected near Perth, Western Australia, in 2021 – apparently three years after the actual introduction. By June 2025 authorities had determined that it was too widespread to be eradicated, so landowners will be responsible for any management.  (Carnegie et al. 2026) Impact is predicted to be greatest in urban landscapes, and cost up to AU$9.7 M per annum to manage.

Pherosphaera fitzgeraldii; photo from https://savingourspecies.environment.nsw.gov.au/managementsite/3752

Phytophthora pluvivora was first detected in Australia on an English oak, Quercus robur. However, it has since been recorded on native species in the Blue Mountains, including the critically endangered dwarf mountain pine (Pherosphaera fitzgeraldii) in a National Park.

SOURCES

Carnegie. A.J., B.A. Summerell, C. Trollip, F. Tovar, D.I. Smith, and J. McDonald. 2026. Sentinel trees for early detection of non-native forest pests and pathogens in Australia. Front. For. Glob. Change 9:1801183. doi: 10.3389/ffgc.2026.1801183

Haack, R.A. and R.B. Blank. 2025.  Susceptibility of English Oak (Quercus robur) to the Twolined Chestnut Borer, Agrilus bilineatus (Coleoptera: Buprestidae): Observations from Michigan. The Great Lakes Entomologist. 57: 113-125. https://doi.org/10.22543/0090-0222.2492

Hernández‐Gutiérrez, E., R.A. Nichols, and L.J. Kelly. 2026. Combined phylogenetic and geographic data can predict plant–pest interactions with high accuracy. New Phytologist (2026) doi: 10.1111/nph.71306

Peyton, J.M., S. Rorke, D.C. Aldridge, O.L. Pescott, K. Dehnen- Schmutz, D.G. Noble,  J. Sewell, A.J.A. Stewart,  T. Adriaens,  B.C. Beckmann,  J. R. Britton, J. Brodie1, P.M.J. Brown, I.C.N. Cavadino, P.F. Clark, A.M. Dunn, J.Foster, C. Harrower, M.C. Harvey, M.C. Jackson, T. Jones, C.A. Maggs, G. Martin, F. Mathews, A.C. Mill, D. Murphy,  E. Paganini, R. Payne, W. Rabitsch, T. Renals,    K. Schönrogge, R.H. Shaw, G.C. Smith, P.D. Stebbing, P.A. Stroh, H. Tidbury, E. Tricarico, J. Vallet,   K.J. Walker, L.E. Wood, C.A. Wood, B. Woodcock, H.E. Roy. 2026. Assessing the success of a horizon scanning approach in predicting invasive non- native species arrival. J Appl Ecol. 2026;63: https://doi.org/10.1111/1365-2664.70217

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

Or

https://fadingforests.org

U.S. Imports from Asia rise … & as more regions expand ports, the pest risk spreads to new places

Pananax ship; photo by 2005emsaguinden via Wikimedia

Imports from Asia, specifically China, had surged in the first half of 2025 as importers tried to get ahead of new tariffs. Blog They then fell sharply, although there was also a shift in Asian suppliers from China to Vietnam and India. At the end of 2025, experts expected the slump to persist into 2026. However, now we learn that U.S. imports from Asia jumped 13% from April to May, to 1.68 million TEUs (Michael Angell, Journal of Commerce, June 16, 2026). According to Politico, the shift to importing goods from Vietnam, and to a lesser extent to Thailand and Indonesia, has continued.

American cities continue to compete for to build larger ports so they can receive more cargo. Of course, more cargo means more incoming containers. As my blogs document (click “wood packaging” in the “Categories” section below the “Archives”), containers and especially the crates and pallets inside them too often transport wood-boring insects and other invasive species.

My source of information on these developments is from the Journal of Commerce website. Unfortunately, access is blocked by a paywall.

Recent reports concern port cities dredging and widening their ports in hope of attracting increased import volumes.

Norfolk; photo by PghPhxNfK via Wikimedia

Norfolk, Virginia

This month the Virginia Port Authority (VPA), Governor Abigail Spanberger and other federal, state, and local officials inaugurated the Port of Norfolk’s expanded capacity. At 55 feet, Norfolk is now the deepest and widest port along the East Coast. The project, begun in 2019, will allow Norfolk to handle vessels carrying up to 18,000 TEUs [twenty-foot equivalent containers]. Authorities are encouraging ocean carriers to call there.

The port was visited by 1,497 container ships over the past 12 months; nearly a quarter had a capacity greater than 11,000 TEUs.

Virginia’s container volumes grew on average 3% annually between 2017 and 2024. In 2025, total container volume fell 8% from 2024 because shippers hoped to avoid tariff deadlines by unloading cargo at a first or second port of call. Virginia was the six-busiest US port for imports this year through May, handling 635,205 TEUs. That was up 2.6% from the same five-month period a year ago. To attract shippers to Norfolk as a first or even second port of call for more container services, Virginia Port Authority CEO Sarah McCoy said, Virginia needs to emphasize rail links. This involves expanding the region’s distribution center network.

The project to dredge and widen the port began in 2019. The total project has a budget of $1.4 billion. The project included adding two ultra-large container vessel (ULCV) berths at each of its two container terminals. The final component is to renovate the North Berth, including developing a fifth ULCV berth, plus four new ship-to-shore cranes and semi-automated stacking cranes in its container yard. Completion is scheduled for mid-2027. At that time, the port’s total handling will reach 5.8 million TEUs. The International Longshoremen’s Association (ILA) is contesting installation of semi-automated stacking cranes in a series of lawsuits.

Other East Coast ports are also adding terminal capacity. This includes the Port of Baltimore, where a shipping company is developing a container terminal that includes handling two ULCVs simultaneously. Apparently they are not deterred by the months-long closure of the Port of Baltimore caused by a ship colliding with a bridge downstream from the port.  

[Information from Michael Angell, Senior Editor, East Coast Ports. “Norfolk aims to be preferred USEC gateway with deeper port” June 18, 2026]

U.S. Army Corps of Engineers dredge in the Savannah River

The Port of Savannah remains dominant. In 2025 Savannah and the roll on-roll of facility in Brunswick together handled nearly 5.7 million TEUs, an increase of 2.6% or 146,000 TEUs compared to 2024. Even so, Georgia Ports is financing a $4.5 billion port and inland infrastructure plan which will add five new container berths in Savannah, the most new berths of any U.S. port and one new RoRo berth in Brunswick. Port officials brag about their rapid turnover of cargo from ship to rail. Forty-two double-stack trains per week take this cargo to Atlanta, Memphis, Nashville, Charlotte and Orlando. The Port Authority also operates two inland terminals – in in Chatsworth and Gainesville, Ga.

Corpus Christi

As I have reported in previous blogs, Gulf Coast ports are also upgrading to receive more shipments. DP World, a Dubai-based terminal operator, is negotiating to develop a container terminal at the Port of Corpus Christi. This would open this port to container logistics.

Corpus Christi is already the third-busiest port in the US by gross tonnage, behind Houston and South Louisiana. The bulk of cargo is petroleum and bulk commodities. (In past years, dunnage associated with bulk commodities proved to cause pest-infestation problems in nearby Houston.)

dunnage piled on the dock at Houston; photo by S. Useman

Last year Corpus Christi completed an eight-year, $625 million project to widen and deepen its main shipping channel (from 47 feet to 54 feet). The expansion allows visits by super-post-Panamax container vessels.

[Information from Michael Angell, Senior Editor, East Coast Ports. “DP World begins talks with Corpus Christi for container terminal project” June 16, 2026]

Warehouse Capacity

Leaders of logistics managers note that importers and domestic manufacturers are diversifying their supply chains – both warehouse facilities and shipping routes – because of ongoing supply chain disruptions even years after COVID 19. While many industrial warehouses across the U.S. still have vacancies (averaging above 7%), some markets are filling up. They mention Chicago, Indianapolis, Memphis, Dallas, and Kansas City. These cities’ warehouse vacancies average ~5%. Indianapolis leads; asking rents for industrial space there have climbed more than 50% over the past five years. Phoenix also anticipates increased demand for space, although its current vacancy rate is 10.6% – the highest vacancy rate of the 25 largest markets.

The move away from Los Angeles-Long Beach began years ago. To move freight inland, shippers need options, particularly access to intermodal rail.

shipping containers at Long Beach in the early 2000s; photo courtesy of Bob Kanter of the Port of Long Beach

The experts attribute this growth to the need for more flexibile supply chains and demand for materials used in constructing data centers. Demand for the second category is reportedly strongest in the Southeast, followed by interior central markets.

[Information from William B. Cassidy, Senior Editor, Trucking. “US warehousing expanding faster at key inland hubs” June 18, 2026]

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

Or

https://fadingforests.org

Bioinvader Threat to Caribbean cacti – Who is Protecting Them?

Photo of infested cactus at Cabo Rojo National Wildlife Refuge, Puerto Rico. Taken August 20, 2018 by Yorelyz Rodríguez-Reyes

For 15 years I have maintained a profile of the Harrisia cactus mealybug Hypogeococcus pungens because it threatens columnar cacti in the subfamily Cactoideae from the Caribbean basin and possibly in the American Southwest and Mexico. My recent attempts to clarify the current situation have been frustrated by the apparent collapse of funding support for scientists trying to conserve these cactus species.

The dry regions of the Caribbean Islands are home to about 100 native cacti, 75% of which are endemic. According to the Center for Plant Conservation, 20 species are listed as threatened by the IUCN. Puerto Rico specifically is home to 14 cactus species, at least three of which are endemic.

How and when the mealybug first invaded the Caribbean and North America is unknown. The presence of the insect now known as H. pungens Hyp-C on Puerto Rico was detected in the Guánica Commonwealth Forest and Biosphere Reserve on the island’s southern coast in 2005 (Zimmerman et al. 2010). However, the actual introduction probably occurred about ten years earlier, in about 1996 (Poveda-Martinez et al. 2022).  See map of locations below.

In the 20 years since then, the mealybug has spread across the island’s dry districts. By 2010, it was estimated to be present on about 1,400 km2. By 2014 – nine years after detection — the mealybug had reached the small island of Caja de Muertos. The most recent survey of which I am aware (date unclear) detected the mealybug on 268 out of 445 cactus plants examined (60%) in 12 out of 39 sites examined (Poveda-Martinez et al. 2022). The mealybug is also killing native cacti on the nearby U.S. Virgin Islands (Poland et al. 2019), although I have found no data on this invasion or its impact.

Below – columnar cacti on St. John, US Virgin Islands; photos by F.T. Campbell

H. pungens Hyp‑C threatens seven of 14 native cactus species in Puerto Rico. Three of the cacti are endemic; two are federally listed as endangered species: Harrisia portoricensis and Leptocereus grantianus (USDA ARS). Since the mealybug’s detection in Puerto Rico, it has caused extensive damage to Pilosocereus royenii (Royen’s tree cactus), Leptocereus qaudricostatus (pitaya), Melocactus intortus (turk’s cap), and an introduced cultivar, Cereus hexagonus. It has caused minor damage to Stenocereus fimbriatus (Zimmerman et al. 2010). These cacti provide food or shelter for endemic bats, birds, moths and other pollinators (Segarra and Ramirez; USDA ARS).

The insect’s attack promotes abnormal gall-like growth on the stem and deformed flowers. These deformations severely affect infested plants’ reproduction and eventually survival (Poveda-Martinez et al. 2022).

Biological Control

When the mealybug was first detected Commonwealth and federal agencies tried to counter it. A search for possible biocontrol agents in the insect’s native range in Argentina began the 2010. While no funds have ever been appropriated for this activity, for several years the U.S. Department of Agriculture supported the work by allocating funds to the Agriculture Research Service Insect Behavior and Biocontrol laboratory in Gainesville, Florida, from broader programs. Dr. Stephen Hight took the lead, working with colleagues in South America. According to Dr. Hilda Diaz-Soltero, then a USDA official, these funds came primarily from the USDA Invasive Species Coordination Program and APHIS Eastern Region. In fiscal years 2017 and 2019, an additional ~$550,000 came in the form of grants under APHIS’ Plant Pest and Disease Management and Disaster Prevention Program. Link Scientists at the Center for Excellence in Quarantine and Invasive Species at the University of Puerto Rico devoted at least a decade to the search.

Scientists focused on two parasitoid wasps, Anagyrus cachamai and A. lapachosus (Hymenoptera: Encyrtidae). A third candidate, the predator Hyperaspis conclusa, was also assessed (Aguire et al.).

Research on the mealybug-wasps interaction uncovered troubling patterns. First, it has long been known that some mealybugs believed to be belong to the species Hypogeococcus pungens feed on columnar cacti while others feed on plants in two unrelated families, Amaranthaceae and Portulacaceae (USDA ARS; Zimmerman et al. 2010). Would the introduced wasps attack the cactus-feeding mealybug in sufficient numbers?

The confusion over how many mealybug species have been introduced – and where – severely hampered development of a program. (The mealybug has been introduced to control invasive cactus in Australia and South Africa. Most sources say it has been highly effective – prompting the initial concern when it appeared on Puerto Rico.) I have been unable to find any information about the status of the candidate biocontrol agents more recent than 2022.

Genetic Conservation

The USDA also partnered with the Naples (Florida) Botanical Garden to collect fruits and vegetative material for ex situ conservation. Rigorous phytosanitary procedures were followed to ensure the absence of the mealybug. Collections of fruits and vegetative material provided 1,298 cacti samples from 13 species, representing 1,173 maternal lines from 91 sites throughout Puerto Rico. A total of 90,720 seeds representing 8 species are banked at the NBG for long-term storage. Propagation of the vegetative material has 56% success, and plants are incorporated into the NBG’s living collections. (These figures include Opuntia cacti that are hosts of a second invasive insect, Cactoblastis cactorum.)  

Genetic Concerns

Scientists now consider Hypogeococcus pungens (Hemiptera: Pseudococcidae) to be a species complex composed of at least five putative species. The species are separated in part by the plants they use as hosts. Two of the complex have apparently been introduced to Puerto Rico: H. pungens Hyp‑C feeds on cacti; H. pungens Hyp‑AP feeds on hosts in the Portulacaceae & Amaranthaceae. Both evolved from putative source populations in Brazil (Poveda-Martinez et al. 2022).

The two species H. pungens Hyp-C and Hyp-AP are currently separated on Puerto Rico by host preferences and climatic niches. They also occupy different geographic areas. Scientists fear that ongoing climate change could allow H. pungens Hyp-C to establish farther into the island’s interior and in a large area in the north. Such range expansion would end the geographic separation. Overlapping of the two species is likely to exacerbate the threat to Puerto Rico’s cacti. Most directly, it would complicate implementation of management strategies, especially biological control. Intermixing of the two species could also facilitate hybridization which might result in more vigorous attacks or a broadened host range. Hybridization is frequent in closely related species (Poveda-Martinez et al. 2022).

The Mealybug is Frequently Introduced

Mealybugs that feed on cacti and believed to be in the species Hypogeococcus pungens made multiple appearances in southern California between 2000 and 2018 – in gardens and in nurseries. Confusingly, CDFA reports interception of the mealybug on alternanthera and ludwigia plants shipped from Florida (CDFA 2018). I have no more recent data. The population in Florida was reported to be present in 16 counties in 2009); it might be the species that feeds on plants other than cacti (Poveda-Martinez et al. 2022). Other populations has been reported in the Dominican Republic (no date) (CDFA 2018); and in Hawai`i in 2005 (Hawaii Department of Agriculture new pest report). A mealybug that feeds on Amaranthaceae and Portulacaceae was detected in 2000 in San Juan, Puerto Rico (Poveda-Martinez et al. 2022).

In the absence of control measures, scientists expect H. pungens Hyp-C to continue decimating Puerto Rican cactus diversity and threaten other cactus rich ecosystems across the Caribbean islands, Central America and, potentially, North America (Poveda-Martinez et al. 2022).

saguaro and organ pipe cacti in Organ Pipe Cactus National Monument; photo by F.T. Campbell

North America has more than 500 columnar cactus species in the Cactoideae (Zimmerman et al. 2010). Some of these cacti are already endangered, e.g., several Pediocactus. Others are totems of the desert, e.g., the saguaro (Carnegiea gigantea) and organ pipe (Stenocereus thurberi) cacti. Picture The larger ones, particularly, play important ecological roles. It is not known how vulnerable individual species are to the mealybug (Golubov pers. comm. January 2011). In Mexico several mealybugs in the same genus are already present. The natural enemies of these mealybugs might be able to attack H. pungens Hyp-C if it invades the country (Zimmerman et al. 2010). Despite the well-founded concern, apparently no funds have been allocated by governments or conservation organizations to studying the vulnerability of these cacti to one or more mealybugs in the Hypogeococcus genus.

The most likely pathway by which the mealybug is spread is the trade in plants for planting (the horticultural trade) (Zimmerman et al. 2010). A decade ago APHIS reported intercepting mealybugs on cactus (primarily on roots) imported from Germany, Peru, and Puerto Rico. APHIS has also intercepted several other mealybugs in the same genus – on plants (including orchids and bromeliads as well as cacti) from Belize, Costa Rica, Ecuador, Guatemala, Honduras, Mexico, Panama, Peru, and Venezuela (USDA APHIS alert).

A decade ago NatureServe and IUCN found that 31% of Earth’s cactus species were threatened with extinction. They named overharvesting (often for the illegal horticultural trade) and destruction of habitat by smallholder livestock ranching and farming. Did not mention predation by introduced insects – although that is now manifest not only in the cactus mealybug but also the cactus moth.

Sources

Aguirre, M. G. Logarzo, S. Triapitsyn, H. Diaz-Soltero, S. Hight, O. Bruzzone. 2023? Effect of egg production dynamics on the functional response of parasitoids

California Plant Pest and Disease Report. 2005. Vol. 22 No. 1. Covering Period from July 2002 through July 2005.California Department of Food and Agriculture. 2018.California Pest Rating for Hypogeococcus pungens Granara de Willink | Harrisia cactus mealybug Hemiptera: Pseudococcidae Pest Rating: A California Pest Rating for Hypogeococcus pungens Granara de Willink | Harrisia cactus mealybug Hemiptera: Pseudococcidae Pest Rating: A

Hawaii Department of Agriculture. 2006. https://hawaii.gov/hdoa/pi/ppc/2006-annual-report/new-pest-detections  (accessed 11/1/10)

Poland, T.M., Patel-Weynand, T., Finch, D., Miniat, C. F., and Lopez, V. (Eds) (2019), Invasive Species in Forests and Grasslands of the United States: A Comprehensive Science Synthesis for the United States Forest Sector.  Springer Verlag.

Poveda-Martinez, D. N.A. Salinas, M. Belen Aguirre, A.F. Sanchez-Restrepo, S. Hight, H. Diaz-Soltero, G. Logarzo,  and E. Hasson. 2022 Geonomic & ecol evidence shed light on the recent demographic history of two related invasive insects. Scientific Reports.

Segarra-Carmona, A.E., A. Ramirez-Lluch. No date. Hypogeococcus pungens (Hemiptera: Pseudococcidae): A new threat to biodiversity in fragile dry tropical forests.

Segarra-Carmona, A.E., A. Ramírez-Lluch, I. Cabrera-Asencio and A.N. Jiménez-López. 2010. First Report of a New Invasive Mealybug, the Harrisia Cactus mealybug Hypogeococcus pungens (Hemiptera: Pseudococcidae). J. Agrie. Univ. RR. 94(1-2):183-187 (2010)

Srivastava, M., P. Srivastava,  R. Karan, A. Jeyaprakash, L. Whilby, E. Rohrig, A.C. Howe,  S.D. Hight, and L. Varone. 2019. Molecular detection method developed to track the koinobiont larval parasitoid Apanteles opuntiarum (Hymenoptera: Braconidae) imported from Argentina to control Cactoblastis cactorum (Lepidoptera: Pyralidae). Florida Entomologist 102(2): 329-335.

Triapitsyn, Aguirre, Logarzo, Hight, Ciomperlik, Rugman-Jones, Rodriguez. 2018. Complex of primary and secondary parasitoids (Hymenoptera: Encyrtidae and Signiphoridae) of Hypogeococcus species. mealybugs (Hemiptera: Pseudococcidae) in the New World. Florida Entomologist Volume 101, No. 3 411

USDA Agriculture Research Service, Research Project: Biological Control of the Harrisia Cactus Mealybug, Hypogeococcus pungens (Hemiptera:pseudococcidae) in Puerto Rico Project Number: 0211-22000-006-10 Project Type: Reimbursable

Zimmermann, H.G., M.P.S. Cuen, M.C. Mandujano, and J. Golubov. 2010. The South American mealybug that threatens North American cacti. Cactus and Succulent Journal. 2010 Volume 82 Number 3

Earthworms – relationships to Pleistocene glaciers

I last blogged about bioinvasions by earthworms in September 2023. My concern was that the USDA Animal and Plant Health Inspection Service (APHIS) was refusing to regulate worms’ introduction based on an inadequate risk assessment. I complained that APHIS’ principal concern was that introduced worms or the soil they were transported in might transport pathogens. APHIS’ website did not mention introduced earthworms’ well-established ability to disrupt the soil and possibly cause undesirable impacts on plant growth and diversity.

I also cited a study by USDA Forest Service scientists regarding interactions between long-term, continuous stressors, including earthworm invasions, and short-term gap-forming events. Reed, Bronson, et al. (2025) reported finding lower earthworm biomass and density in both deer exclosures and canopy gaps. They hypothesized that in canopy gaps higher deer browse pressure changed plant community and soil properties. These changes then affect soil-dwelling fauna like earthworms. They believed the higher worm densities in closed-canopy sites might be the result of greater volumes of nutrient-rich tree leaf litter which provides both shelter and food. The closed canopy sites also lacked recent soil disturbances. (Other authors cited in that blog describe varying impacts of deer browsing on plant communities and succession.)

A study I have not previously included in my blogs focused on invasions in the forest understory of the Katharine Ordway Natural History Study Area, which is in eastern Minnesota on the bluffs of the Mississippi River. The now dominant oaks are being replaced by a more mesic forest with a growing proportion of Ulmus americana, U. rubra, Acer negundo, Prunus serotina, Tilia americana, and Fraxinus pennsylvanica. (I note that three of these species are being suppressed by two introduced organisms, “Dutch” elm disease and emerald ash borer).  

Davis et al. (2015) found that all common herb layer species – native and non-native – established in microsites favorable to plants in general. Under the forest’s mostly closed tree canopy, light levels played almost no role in determining where herbaceous understory plants grew. However, abundant earthworms and deer were deemed to be larger factors explaining most of the changes in native herbs’ abundance and distribution. The earthworms’ effect arose from changes to the soil and litter environment.

I have not found a more recent analysis of the Ordway forest understory, so I don’t know whether these trends continued. I also wonder whether the conclusions about herb species’ interactions would have differed if the non-native species studied were those that completely dominate the ground level, such as Ficaria instead of Alliaria petiolata; or a dense shrub layer, e.g., Rosa multiflora.

A new analysis provides a large-scale description of worm invasions. McCay et al. (2026) report that about 300 species of earthworms inhabit North America, of which about 70 are non-native. They sought to determine the relative importance of Pleistocene glaciation in explaining earthworms’ present assemblages. Their study sampled 94 sites across 13 states of the eastern and central U.S. over a twelve year period (2013 – 2025). Seventy-four of the sites were located in previously-glaciated locations, 20 sites in non-glaciated places.

The study confirmed the presence of 16 species; only three were considered to be native to North America (Aporrectodea rubidus, Eisenoides carolinensis and E. lonnbergi). Minimum species richness at individual sites ranged from zero to eight species. Species richness was markedly greater in the glaciated regions of the Midwest and Northeast. By both dry biomass and numbers, European lumbricids dominated throughout. Lumbricus species constituted 45% by number and 69% by biomass across all sites. Their dominance was highest in the Midwest Glaciated region.

Native earthworms were rare, constituting only 2 or 3% at those sites where present. Invasion by Asian pheretimoid megascolecid (“jumping worm”) species has just begun; they were present at only 10% of study sites.

Earthworms – apparently both native and non-native – were most abundant and diverse in the Midwest Glaciated region (Ohio, Michigan, Minnesota, and Wisconsin), where non-indigenous earthworm invasion is more recent than in the Northeastern Glaciated Region (Massachusetts and New York). Earthworms were least common and diverse in areas south of the terminus of the Pleistocene glaciation. McCay et al. (2026) speculated that development of forests in northern North America over thousands of years with few or no earthworms might have led to accumulations of organic matter in forms useful to earthworms (“banking” of soil organic matter), which supported a pulse of earthworm proliferation following colonization. 

Some other factors play a role.  Earthworm presence – measured by biomass – and diversity increased with higher soil pH. Many earthworm species are known to be sensitive to soil acidity. Epigeic earthworms (those that feed on leaf litter) are often more tolerant of acidic conditions than endogeic earthworms (which live in and consume soil).

The study did not measure co-occurring variables such as calcium abundance, buffering capacity, or exchangeable aluminum. All might more directly affect worms’ physiology than pH per se.

Soil structure also matters. Soil-feeding species might be disadvantaged by sandy and gravelly soils, which do not support persistent burrow formation and are often nutrient deficient. On the other hand, they thrive better in clay soils.

While each study participant established at least one site in a relatively undisturbed habitat, e.g., a mature forest, the majority of sites tended to be within a disturbed landscape, less than .8 km from a road.

Earthworm abundance and activity vary seasonally but only 4 sites were observed over more than one season. Across all sites, there was greater species richness in autumn and spring than summer. McCay et al. (2026) think that this might have been because many earthworms aestivate during dry weather, so they are less detectable during summer although they are still present.

Distribution of native North American earthworms suggests there was some natural colonization of previously glaciated landscapes before European people arrived.

McCay et al. (2026) also did not document land use history at the sampling sites, although that can profoundly affect worms and vertical distribution of carbon in the soil. Nor did their habitat classification system [deciduous and coniferous forests, mowed and unmowed grasslands] describe the vegetation in sufficient detail to determine whether food quality might have been a factor. It is recognized that litter varies in C:N ratios, lignin content, and palatability.

McCay et al. (2026) note an interesting pattern at the global scale: Australia, New Zealand, South Africa and North America (U.S. and Canada) have been invaded by the same suite of invasive European earthworm species. One common factor, not addressed by the scientists, is that all were settled by British colonists. Instead, they focus on ecological factors. They suggests that the species’ niche requirements are broad and well-matched to temperate forest soils worldwide, and that climate and soil conditions, rather than biotic resistance from native communities, are primary factors limiting their distribution and abundance.

Another factor supporting this hyptothesis, in their view, is that the composition of earthworm communities was relatively similar above and below the southern glacial limit in North America.  Here, European earthworms colonized not just the relatively “open” soils of previously glaciated north but also non-glaciated areas farther south – assisted by human introductions and creation of disturbed habitats. They suggest that the novel species might have benefitted from reduced competition because the European species had functional differences from resident native species.

The current rapid expansion of “jumping” earthworms in North America is a fundamentally different invasion wave than the centuries-old invasion by European lumbricid species. The Asian pheretimoid species reproduce parthenogenetically and have shorter generation times. They achieve high population densities at the soil surface, process organic matter rapidly, and create a loose casting layer, potentially creating different soil conditions in ways not true after invasion by European earthworms. Although it is too early to know the outcome, McCay et al. (2026) note emerging evidence that the Asian pheretimoids might outcompete European earthworms through more flexible resource exploitation, preemptive foraging during the late summer and early fall, and tolerance of environmental stress.

Effects on atmospheric carbon levels

McCay et al. (2026) point out that the introduced earthworms are disrupting the significant pool of accumulated organic matter in previously glaciated soils. As earthworms move in, they facilitate more rapidly cycling but also translocate carbon into deeper soil strata. They conclude that while earthworms initially accelerate carbon loss through increased decomposition and respiration, their long-term effects might protect soil carbon storage. Earthworm casts and burrows can create microsites with different oxygen and moisture conditions that might promote carbon stabilization through different mechanisms than the original forest floor.

SOURCE

Davis, M.A., M.D. Anderson, L. Bock-Brownstein, A. Staudenmaier, M. Suliteanu, A. Wareham and J.J. Dosch. 2015. Little evidence of native and NIS species influencing one another’s abundance and distribution in the herb layer of an oak woodland. Journal of Vegetation Science · June 2015

DOI: 10.1111/jvs.12302

McCay, T.S., Anderson, L.J., C.P. Bloch, A.E. Cahill, S.L. Cooke, B.J. Dolan, K.M. Flinn, D. Garneau,  N.J. Hains, K. Hopfensperger, M.Beth Kolozsvary, C. Mankiewicz, S.E. Scanga, J.L. Schafer, E. Schwartzberg, D.A. Scott, K.L. Shea, J. Simmon, J.N. Styrsky. 2026. Earthworm assemblages in the Eastern and Midwestern United States and the legacy of glaciation. Biol Invasions (2026) 28:91 https://doi.org/10.1007/s10530-026-03798-3

Reed, S.P., D.R. Bronson, J.A. Forrester, L.M. Prudent, A.M. Yang, A.M. Yantes, P.B. Reich, and L.E. Frelich. 2023. Linked disturbance in the temperate forest: Earthworms, deer, and canopy gaps

Ecology. 2023;104:e4040. https://onlinelibrary.wiley.com/r/ecy  

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

Or

https://fadingforests.org

Eastern Canada: major threat from climate-driven insect invasions

eastern (Canadian) hemlocks in Nova Scotia killed by hemlock woolly adelgid; photo by Celia Boone, NSDLF

Two recent studies show that climate change is driving changes to pest ranges. These pose a serious threat to forests of eastern Canada.

A study by Aubin et al. (2026; full citation at end of blog) assessed the risk that climate change would exacerbate the impacts of 14 non-native forest insect pests  The 14 insect species were selected from an original group of 76 species using the following criteria: 

1) They have the potential to cause mature tree mortality to at least one of the 37 tree species most abundant in Canada; and

2) They have been detected in Canada recently or have established populations actively spreading through the Canadian landscape.

Major Findings

Twenty-four tree species are affected currently by at least one of the 14 non-native insect pests (excluding Asian longhorned beetle; see below). (I list the tree and insect species below.) Four of them are already considered globally endangered or threatened due to invasive pests: black and white ash (Fraxinus nigra and F. americana), whitebark pine (Pinus albicaulis) and eastern hemlock (Tsuga canadensis). Another ash species (blue ash; Fraxinus quadrangulata) and another pine (limber pine; Pinus flexilis) are considered rare or threatened species in Canada.

brown spruce longhorned beetle; photo by Udo Schmidt via WikiMedia

Of the 24 species at risk, black spruce (Picea mariana) is most exposed because it grows in areas where eastern spruce gall adelgid and brown spruce longhorned beetle (Tetropium fuscum) are established. Expansion of these two pests could potentially reach 75% of black spruce biomass in Canada. However, Aubin et al. (2026) expect tree mortality to be limited because these insects target trees that are already stressed or weakened. Of course, the changing climate might increase the trees’ susceptibility. Thirty percent of the black spruce’s range is projected to be outside its current climatic niche by 2040.

The 24 tree species currently affected by at least one of the 14 non-native insects (excluding ALB) collectively constitute 3.2 billion tons of tree biomass. The impact is projected to increase more than four-fold — to 13.6 B tons of biomass — within two decades. Reinvasion by the Asian longhorned beetle would put at risk six additional tree species in the genera Acer, Betula, and Populus. Their jeopardy would add another 3.1 billion tons of live tree biomass to the “at risk” category.

Aubin et al. (2026) note that affected trees might remain alive but moribund, that is, lose their functional role within the ecosystem. for several years before finally dying. Therefore their analysis might underestimate pests’ impact on the forest. Their example is American beech – as weakened by beech bark disease. A reminder: beech bark disease causes widespread death of mature beech – opening the canopy and eliminating such wildlife-supporting aspects as nesting cavities and abundant crops of nuts. Vigorous root sprouting results in dense stands of young beech, crowding out other species.

Hotspots of greatest vulnerability

The analysis identified two hotspots of greatest vulnerability: north-central British Columbia near the border with Alberta, and along the St. Lawrence Seaway near the border with the United States. The pest pressures differ.

The threat to the British Columbia hotspot comes from expansion of mortality in dense pine forests caused by the native mountain pine beetle (Dendroctonus ponderosae). Aubin et al. (2026) describe a two-pronged impact from the changing climate: trees lose vigor because they become maladapted to the new growing conditions (temperature and drought); while the beetle increases the frequency of outbreak due to reduced overwintering mortality. 

Along the St. Lawrence Seaway (southern Ontario and Quebec) the threat comes from a suite of non-native insects, including emerald ash borer, hemlock woolly adelgid, and beech scale. While emerald ash borer and beech scale were introduced directly to Canada by international trade, hemlock woolly adelgid spread across the border from the U.S. Further northward expansion of all three is projected under both low and high emission climate change scenarios.

beech bark disease in New Hampshire; photo by Eli Sagor via Flickr

Most alarming is that some regions in eastern Canada are vulnerable to invasion by all 14 insect species. Two additional pests loom: Aubin et al. (2026) fear northward expansion might reintroduce the Asian longhorned beetle or introduce the southern pine beetle (Dendroctonus frontalis). The latter has been expanding northward in the U.S.

Pests often move across the Canada-U.S. border. In addition to the five pests mentioned above, spongy moth, and two pathogens, the beech leaf disease nematode, and the oak wilt fungus, have spread from the U.S. into neighboring parts of Canada. The woodwasp Sirex noctillio was probably introduced simultaneously to both countries. Winter moth and beech bark disease spread from Canada to the U.S. I worry that the brown spruce longhorned beetle might do the same.

Asian longhorned beetle: can this disaster be averted?

As noted above, the Canadians are alarmed by the prospect that the Asian longhorned beetle might be reintroduced – either by spread from extant populations in the United States or directly on imports from China. Aubin et al. (2026) note that the two earlier – successful! — eradication programs were expensive, costing an estimated CND$35.5 million. This expenditure is dwarfed by the costs estimated to arise from an unmanaged invasion: CDN$431 million annually in timber products and CDN$358 million annually in edible maple products. There would also be enormous ecological impacts, including threats to an additional 3,08 metric tonnes of tree biomass comprising ~24.96 tons of CO2 equivalent.

Canada’s central boreal forest is at lower risk both in terms of exposed tree biomass and number of invasive insect species present. The reasons are not understood. Aubin et al. (2026) suggest that the boreal ecosystem is more resistant to invasion due to a combination of environmental barriers and native natural enemies. For example, the introduced woodwasp Sirex noctilio did not cause widespread pine mortality in the region, probably due to antagonistic interactions with other subcortical species.

Species’ Details

The 14 insect species the authors studied are: 

Adelges abietis, Adelges tsugae, Agrilus planipennis, Agrilus sulcicollis, Coleophora serratella, Dendroctonus ponderosae (they include climate-change-related range expansion), Diprion similis, Neodiprion sertifer, Operophtera brumata, Cryptococcus fagisuga-Neonectria coccinea, Tetropium fuscum,  Coleophora laricella, Acantholyda erythrocephala.

Although it does not fit this definition, Aubin et al. (2026) also evaluated the Asian longhorned beetle (ALB Anoplophora glabripennis), because of its huge impact if it is reintroduced to Canada (see above).

One of the focal groups, beech scale, Cryptococcus fagisuga, differs from the others because it is a vector of a tree-killing fungal pathogen (Neonectria coccinea); the scale itself does not cause notable harm.

Aubin et al. (2026) acknowledge that additional species represent a possible threat to Canadian forests. Therefore their study does not represent the total risk posed by all potential invasive insects in Canada, but provides a snapshot of selected, current vulnerabilities.

The 37 most abundant tree species in Canada together represent 88% of total mature forest tree biomass in Canada. They include 17 conifers and 7 deciduous trees: 

Abies amabilis, Ab. balsamea, Ab. lasiocarpa; Acer rubrum, Ac. saccharinum, Ac. saccharum; Alnus rubra; Betula alleghaniensis, B. papyrifera; Callitropsis nootkatensis; Fagus grandifolia; Fraxinus american, F. nigra; Larix laricina, L. occidentalis; Picea engelmanii, P. glauca, P. mariana, P. rubens, P. sitchensis; Pinus albicaulis, P. banksiana, P. contorta, P. ponderosa, P. resinosa, P. strobus; Populus balsamifera, P. grandidentata, P. tremuloides; Pseudotsuga menziesii; Quercus rubra; Thuja occidentalis, T. plicata; Tilia Americana; Tsuga canadensis, T. heterophylla, T. mertensiana

The 14 insects collectively have 63 host tree species in Canada. The pine genus is susceptible to the largest number of pests. Genera found to be not vulnerable to any of the 14 insects are Acer, Callitropsis, Populus, Pseudotsuga, Tilia, and Thuja. The proportion of total exposed tree biomass in Canada varied by species, from 8% of Jack pine (Pinus banksiana) to 95% for red spruce (Picea rubens).

red spruce in West Virginia; photo by Famartin via WikiMedia

Although most of the 14 insect species are projected to benefit from larger areas of suitable climate in Canada over the next 20 years, there are interesting exceptions: European oak borer (Agrilus sulcicollis), brown spruce longhorned beetle, and winter moth (Operophtera brumata). Distributions of the host tree species are projected to change insignificantly over the 20 years covered by the study.

With northward expansion of suitable climates for 12 of the 14 species, large areas of the boreal forest will be exposed to potential invasion. The entire Canadian distribution of 13 of the 37 dominant tree species might be at risk: three Abies, two Betula, both Fraxinus, Picea mariana, Pinus contorta, Picea glauca, Pinus banksiana. Aubin et al. (2026) mention specifically Engelmann spruce (Picea engelmanii) and American beech (Fagus grandifolia).

Other Factors

The analysis did not consider possible alterations of the insects’ life history traits other than potential expansion of their distributions. Warmer temperatures can cause changes in voltinism, diapause periods, development rates, reproduction, and population growth; cumulatively, these changes might alter their invasion dynamics. The mountain pine beetle is an example. Populations have experienced outbreaks more frequently, so increasing the species’ invasion threat and severity. On the other hand, shifts in temperature and precipitation could decouple the phenology of trees and their associated pests, reducing insect survival. Finally, complex changes in tree tissue and their secondary defensive metabolites (see below) also could alter interactions between non-native insects and their new hosts – possibly exacerbating or mitigating the herbivores’ impacts.

Aubin et al. (2026) remind us that loss of a dominant species might lead to reorganization of forest composition and structure. They expect the impacts to be particularly critical in stands with low tree diversity, such as the pure jack pine stands in the eastern boreal forest. Loss of a foundation species might also profoundly disrupt ecosystem functions, carbon budgets, wildlife habitats and stand productivity. They cite cascading effect on aquatic invertebrate communities and invasions by non-native plant species following widespread death of ash trees caused by the emerald ash borer. Finally, death of some species reduces functional redundancy within tree communities, and a shrinking pool of viable native replacement species. The widespread planting of ash trees in urban areas after the demise of most elms is such a case.

American elms in Jeanne d’arc Park, Quebec; photo by Cephus via Wikimedia

The possibility that the tree hosts might increase production of defensive metabolites was corroborated by Mike Aucott in a different context. Dr. Aucott is retired from the New Jersey Department of Environmental Protection. He authored a guest blog in December 2022, in which he discussed changes in plant chemistry brought on by the 50% increase in atmospheric CO2 levels over the last century. By happenstance, Dr. Aucott engaged in an exchange of letters in Science (2/26/26), in which he reiterated the likelihood that plants, “fertilized” by access to this nutrient, might be better able to fend off insect attacks. (See the “Sources” section for references to additional information on this phenomenon.)

Compounding Threat: The Spruce Budworm in Eastern Canada

The spruce trees of eastern Canada face another pest threat: the native spruce budworm (SBW, Choristoneura fumiferana). It is already a major defoliator in North American boreal forests.

Boulanger et al. (2025; full reference at end of this blog) documented pronounced changes in the moth’s range, especially in the East. Over the past 60 years, suitable climate conditions for the budworm have expanded northward. On the other hand, winter mortality has increased in southern parts of its range due to warmer temps. Overall, the total area highly suitable for population growth remained virtually the same. Still, the budworm’s earlier activation might exacerbate its impact on the previously less vulnerable black spruce, Picea mariana. If so, this might fuel further increased population growth rates northward.

black spruce; photo by Laval University via WikiMedia

Like Aubin et al. (2026), Boulanger et al. (2025) found that Canadian forests in the east and Atlantic regions are likely to experience greater impacts on tree growth than are forests in western and central regions. The host most vulnerable to SBW, balsam fir (Abies balsamea), is a dominant or codominant species in the East and Atlantic regions. The fir is sparsely distributed in those areas of central and western Canada where the climate is becoming highly suitable for the insect. The frequent wildfires promote growth of young pioneer tree species, e.g., jack pine and trembling aspen, that do not support SBW.

At the most general level Boulanger et al. (2025) suggest that climate change might have already surpassed impacts of land use change on spruce budworm dynamics. Climate change puts additive and synergistic pressures on insects, which are already more sensitive than trees to climatic factors and able to adapt more quickly. As a result, climate change is becoming the most significant driver of recent declines in insect abundance and shifts in community structure, development, dispersal patterns, and phenology. (Again, see Aucott, above, for an alternative explanation.)

Boulanger et al. (2025) mention but do not discuss possible impacts of climate change and a shift in SBW distribution and tree hosts on a third trophic level, i.e., natural enemies. They note that many factors – not just climate suitability — influence trophic interactions. Another complication is that most SBW parasitoids require alternate hosts.

Boulanger et al. (2025) join others in urging forest managers to quickly adapt their management strategies to the novel climate-induced threats. They call for a proactive and integrated approach in forest management. Ecological research will be crucial to mitigate the compounded effects of climate change and to preserve the integrity & sustainability of forest ecosystems.

SOURCES

Aubin, I., A. Roe, B. Marquis, L.  Boisvert-Marsh, J. Pedlar,S. Erni, B. Hamel, G. Lawrence, D. McKenney, T. Scarr. 2026. Vulnerability of Canadian forests to invasive insects under climate change. Accepted by the Canadian Journal of Forest Research.

Aucott’s letters to entomology journals: https://academic.oup.com/ee/article-abstract/48/2/274/5372493 & https://www.sciencedirect.com/science/article/abs/pii/S0006320720302822?via%3Dihub 

Boulanger, Y., A. Desaint, V. Martel, M. Marchand, S. Massoda Tonye, R. Saint-Amant, et al. (2025) Recent climate change strongly impacted the population dynamic of a North American insect pest species. PLOS Clim 4(2): e0000488. https://doi.org/10.1371/journal. pclm.0000488

Ziska, Lewis. 2022. Greenhouse Planet https://cup.columbia.edu/book/greenhouse-planet/9780231556613/ (book)

See also an article describing declining nutrient value of food crops in response to increased atmospheric C02 levels: https://www.washingtonpost.com/climate-environment/interactive/2026/carbon-pollution-diluting-key-nutrients-food/

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

Or

https://fadingforests.org

Webinar: how you can help restore eastern hemlocks

The Wildlife Society’s Invasive Species and the Forestry and Wildlife Working Groups are cosponsoring a workshop for the Lingering Hemlock Project. The workshop will be on Tuesday 28 April at 2:00 PM EDT.

The Lingering Hemlock Project is a subset of The Nature Conservancy’s “Tree Species in Peril” program. The project aims to locate and selectively breed eastern hemlocks with genetic resistance to the hemlock woolly adelgid (HWA).

Olivia Hall from the North Carolina Hemlock Restoration Initiative will share more about how natural areas can participate in the Lingering Hemlock Project. In the southeastern US, project partners can locate and record data on hemlocks that remain healthy despite HWA infestations. In the northeastern US, project partners can establish hemlock plots and monitor their health and decline annually.

Go here to learn more about the project & webinar, and find the link to join.

I have blogged about HWA often – although there is no simple method for finding the earlier blogs. In 2025 I posted 3 blogs – in March and one in August. If you need a reminder about HWA, visit TNC’s “don’t move firewood” website 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.

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

Or

https://fadingforests.org

Help Minnesota track invasive jumping worms

Amynthas agrestis; photo by John Abrams via Wikimedia

The University of Minnesota is seeking to learn the extent and impact of invasive Asian jumping worms (Amynthas spp.). Scientists fear that jumping worms will remove the naturally deep litter layer and create  extremely loose soils that cannot be held by plant roots. These changes will expose soil on the state’s hillsides to erosion by human footsteps, rainfall, and water runoff. They worry about the future sustainability of forested hills in Minnesota. 

The research project began in January 2024; it is funded at $430,000. The research seeks to answer the following questions:

  • What is the magnitude and rate at which jumping worms accelerate soil erosion in forested hillslopes in Minnesota?
  • What are the mechanisms of soil erosion by jumping worms in hardwood forests?
  • What is the spatial extent of jumping worms in forested hillslopes?
  • What species of native plants are capable of holding soils against jumping worms and could act as erosion-prevention?
  • What management practices could help to reduce soil erosion induced by jumping worms in forested hillslopes?

The scientists are asking volunteers to actively look for jumping worms in the forests of southeastern Minnesota and report them to EDDMapS.

Boundary Water Canoe Area; photo by Chad Fennell via Wikimedia

The scientists remind us that invasive European earthworms have already infested nearly all of the state’s  forests, even in the remote Boundary Waters Wilderness. Forest soils and understory vegetation transformed, and invasive earthworm impacts are cascading through ecological and socio-economic processes. They expect the state to become divided into two distinct areas, each dominated by a different invasive earthworm group.

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

Or

https://fadingforests.org

What is happening to spicebush?

Lindera benzoin; photo by Fritzflohrreynolds via Wikimedia

Scientists in Ohio and other states are trying to determine what is causing dieback of the native shrub northern or common spicebush (Lindera benzoin). The shrub occurs throughout much of the eastern United States and neighboring parts of Ontario, Canada.

In May 2024, Ohio State forest entomologist Kayla Perry and Cleveland Metroparks Natural Resources Area Manager Josh Philipps observed red thrips and dieback symptoms on spicebush in the reserve. The website includes many photographs of the damage. [Interesting note: beech leaf disease was also first detected in Cleveland Metroparks.] Later in the season similar symptoms were detected at Holden Arboretum and in other units of Cleveland Metroparks properties across three Ohio counties, Cuyahoga, Lake, and Medina. Constance Hausman, Senior Conservation Science Manager with Cleveland Metroparks, reported seeing dieback on spicebush at other reserves in Lake, Ashtabula, and Geauga Counties, suggesting the problem is likely more widespread.

At some locations, large populations of thrips were found on a few plants where they were congregating on the underside of the leaves. While some of the plants show twig dieback, other plants wilt. Some had chlorotic leaves with a mottled pattern. Other symptoms included black necrosis of the petioles and some vein spotting. Similar dieback and viral symptoms observed at other parks within the region. At an arboretum in Wooster, symptoms were seen but no thrips were observed on those plants. As of December 2024, there was no evidence of a connection between the dieback symptoms and the presence of the thrips.

Ohio State entomologists identified the thips as nymphs belonging to the suborder Tubilifera or tube-tailed thrips. National Identification Services (NIS) confirmed the identification as Pseudophilothrips in the family Phlaeothripidae. However, a species determination could not be made due to the limited genetic database of Thysanoptera in GenBank or BOLD.

Some of the symptoms are often associated with a viral infection. Examination of a few twigs found no signs or symptoms of black twig borer (Xylosandrus compactus). Culture plates showed the growth of Colletotrichum sp., a well-known pathogen capable of infecting a wide range of host plants and causing various host-specific symptoms — often referred as anthracnose. The C. Wayne Ellett Plant Pest Diagnostic Clinic did not observe the characteristic vascular streaking associated with vascular streak dieback, a fungal disease caused by Ceratobasidium theobromae. (Spicebush with these symptoms were detected on 30 years ago at two locations in southwestern Ohio, but the cause was not determined.)

Scientists at USDA-ARS were testing symptomatic samples for another possible agent, the recently discovered Emaravirus. The December 2024 article said results were pending. However, at the February 2026 USDA Annapolis, participants reported no breakthroughs.

As of late 2024, symptomatic plants had been detected in Kentucky, Missouri, and Virginia, as well as Northeast Ohio. I believe Maryland has also found symptomatic spicebushes.

Lindera species are also threatened by laurel wilt disease, which is spreading north.

The three spicebush species are hosts for several native swallowtail butterfly species and other pollinators, including spicebush swallowtail (Papilio troilus), eastern tiger swallowtail (Papilio glaucus), and promethea silkmoth / spicebush moth (Callosamia promethea). I believe the shrubs support largely the larvae of these species. The grubs of the sassafras borer (Oberea ruficollis) will bore into the shrub’s branches and roots.

Spicebush is one of the first shrubs to bloom in Pennsylvania forests. I have found no information concerning the plants’ importance to early season pollinators other than the butterflies.  

grey catbird; photo by Wilfred Hdez via Flickr

The red, shiny, elliptical fruits with a single seed (drupes) are nearly 50% fat. They become ripe in the fall, so a great fuel source for fall migrants and over-wintering resident birds, including wood thrush (Hylocichla mustelina), veery (Catharus fuscescens), northern bobwhite (Colinus virginianus), and gray catbird (Dumetella carolinensis). Eastern cottontail (Sylvilagus floridanus) and other small mammals might feed on the leaves, twigs, and berries. Other sources also mention deer. However, the spicy, sweet scent produced by the stems and foliage might deter some animals. 

Spicebush leaves and berries can be used as a spice when cooking. Native Americans protected these plants used the plants to treat colds, coughs, and dermatological and respiratory ills.  

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

Or

https://fadingforests.org

Funding key agencies – Your help needed!

EMERGENCY:

The Trump Administration proposes (again!) to end all funding for USFS Research and State, Private, and Tribal Forestry programs. The budget document claims that these cuts are necessary “to ensure fiscal responsibility w/ taxpayer dollars & appropriate alignment of resources w/ USFS’s responsibility to appropriately steward National Forest System lands.” Ending the SP&T programs is justified as “better balance[ing] the appropriate roles of federal & State governments. … and [restoring] federalism …] The document claims that the federal component of Forest Health Management [currently receiving $16 million] duplicates programs managed by the National Forest System; yet the actions listed under this second budget category all relate to water management, not insects or pathogens. The document says states should manage pests on non-federal lands [currently receives $42 million]. I think this approach ignores the need for coordinated management for each of hundreds of pest species, from detection to eradication or development of host resistance. Eliminating the Research program will deprive all forest managers of a scientific foundation for management efforts.

The Trump Administration’s proposed budget would hold funding for key APHIS programs steady. This is great news compared to the extreme cuts proposed for the Forest Service. The budget document says that it is essential to continue APHIS programs success; any stoppages or reductions would potentially cause catastrophic consequences for environmental health. Contrary to this statement, holding funding steady actually results in cuts due to continuing introductions of new pests and inflation.

Item2024  Actual2025  Actual2026  Estimated2027  Estimated
Field Crop & Rangeland Ecosystems Pests (incl cogongrass)………. 12,00012,00011,0009,026
Pest Detection ……………………………………………….. 29,00029,00029,00029,000
Plant Protection Methods Development …………………. 21,50021,50021,50021,500
Specialty Crop Pests ………………………………………… 215,000215,000214,000217,339
Tree & Wood Pests ………………………………………….. 59,00059,00058,65058,650
Subtotal, Plant Health ……………………………………. 387,500387,500385,150386,515

USDA Forest Service

Two USFS programs w/ vital roles in protecting resilience of the Nation’s forests in the face of invasions by non-native pests and plants: R&D program and FHM within SPT division

The many economic & ecological benefits from our forests are under growing threats from a variety of disturbances, ranging from fires & hurricanes to non-native pests. ~ 60% of forests owned by non-feds; USFS must address threats to forests outside NFS to achieve its mission of sustaining “health, diversity, & productivity of the nation’s forests & grasslands to meet the needs of present & future generations.”

Research & Development

The Continuing Resolution for FY26 funded Research at $308 million for the year. Ask Congress to maintain this level. + increase research on invasive species from the current level of 1% to 5%.

The area of our forests & woodlands that is threatened by alien pests is similar to that attributed to fire or western bark beetles. More than 41% of forest biomass in the “lower 48” states is at risk to established non-native pests.[1] If able, add reference to pests on Hawai`i or Caribbean islands. Since additional introductions almost guaranteed, even greater proportion of US’ forest resources at risk in future. If possible, name example, e.g., Phytophthora austrocedri. Forest managers cannot counter these threats without understanding how these P&P kill trees & what actions are effective counter measures. This knowledge is obtained by research.

At least 53 tree species in forests across America are already under attack by non-native pests and pathogens. Yet as of FY23, Research stations spent just 1% of appropriation studying a few of the dozens of NIS pests. Funding for alien pests has decreased 70% since FY2010 even as new pests enter our forests. This inadequate research effort means USFS cannot develop effective programs to prevent, suppress, & eradicate the majority of alien pests. One crucial strategy suffers particularly = efforts to breed trees able to thrive despite NIS pests. R&D currently supports only a few such projects.

Forest Health Management: Supporting the Full Continuum of Pest Management

The Continuing Resolution for FY26 funded State, Private, and Tribal forests program at $310.6 million. I have not found specifics for the FHM program. This was an increase over the $281 million level in FY25.

Non-native pests and pathogens arrive as contaminants or hitchhikers on imported goods, especially on wood packaging and plants. These imports usually arrive in cities or suburbs, so the pests establish there first. They immediately cause enormous damage to urban forests, forcing local governments and property owners to absorb high tree removal costs. They then spread to rural forests, including National forests. Examples include hemlock woolly adelgid, emerald ash borer, invasive shot hole borers, goldspotted oak borer, sudden oak death, and beech leaf disease.

The most effective approach is to kill the pests where they first appear – usually in those urban or semi-rural forests. This response is led by FHM Cooperative Lands subprogram. We urge maintain funding for this subprogram at the FY26 level (possibly $42 million) so that the agency’s experts can continue to assist the states and other partners in countering these pests. As these pests spread to rural areas – including to National forests, National parks, and other public lands, responsibility for their management involves FHM Federal Lands subprogram. So much maintain funding for this subprogram at FY26 levels.

A recent analysis[2] determined that the natural resource values of 92 National parks are threatened by forest pests. Western parks are threatened primarily by outbreaks of the native mountain pine beetle (Dendroctonus ponderosae). Those in the East face threats from more than a dozen species of non-native pests, including hemlock woolly adelgid, emerald ash borer, spongy moth, laurel wilt, and – most recently – beech leaf disease.

Again, combatting these pests requires understanding their life histories & traits – understanding gained through the research program mentioned above.  

Funding reductions over the past decade have already shrunk the number of FHM projects & areas treated each year. While 53 tree species are threatened, only four [eastern oaks, loblolly & ponderosa pines, & hemlocks] are targeted by 95% of projects. To counter the threats to 50 additional tree taxa, FHM needs additional resources.[3]

Investing in urban forestry is key to addressing both parties’ priorities & advancing flexible & cost-effective solutions to a wide range of issues impacting American communities, businesses, & families. The USFS SPT division’s Urban & Community Forestry Program efficiently distributes funds to shovel-ready projects for improving communities by maintaining a healthy tree canopy. Federal “seed” money provides resources necessary to initiate & stabilize these local programs.

Breeding Resistant Trees: Critical — & Underfunded

A surprisingly high proportion of the (inadequate) funding for breeding trees to mitigate the damage caused by non-native pests is from FHM or the NFS, rather than R&D. These programs should receive  substantial increases. The model program is the Dorena Genetic Resource Center. It provides decades-long commitment, skilled staff, necessary facilities; these result in breeding successes, i.e., western white pines and Port-Orford cedar.  

Invasive Plants

Invasions of forests by non-native plant species erode forest productivity & provision of the full range of ecosystem services, hinder forest uses, degrade biodiversity & habitat, and impose substantial financial costs. A recent analysis[4] documents that this threat is growing: the number of FIA inventory plots containing invasive plant species rose in 58.9% of surveyed counties. Furthermore, in 73.2% of the counties the plots experienced an increase in species richness of invading plants. Increases occurred in all regions, but were greater in the East: from 46% to 52.3%. In the Rocky Mountains, the proportion of invaded plots rose from 6% to 11%. In Hawai`i, this proportion grew from 70% to 83.2%. Again, USFS Research and FHM programs, working together, are key to making progress in countering these bioinvasions.

[1] Fei, S., R.S. Morin, C.M. Oswalt, and A.M. 2019. Biomass losses resulting from insect and disease invasions in United States forests. PNAS August 27, 2019. Vol. 116 No. 35  17371–17376

[2] Michalak, J.L., C.E. Littlefield, J.E. Gross, T.G. Mozelewski, J.J. Lawler. 2026. Relative Vulnerability of US National Parks to Cumulative & Transformational Climate Impacts. Conservation Letters, 2026 Vol 19, Issue 1; 19:e70020

[3] Coleman, T.W, A.D. Graves, B.W. Oblinger, R.W. Flowers, J.J. Jacobs, B.D. Moltzan, S.S. Stephens, R.J. Rabaglia. 2023. Evaluating a decade (2011–2020) of integrated forest pest management in the United States. Journal of Integrated Pest Management, (2023) 14(1): 23; 1–17

[4] Potter, K.M., B.V. Iannone III, K.H. Riitters, Q. Guo, K. Pandit, C.M. Oswalt. 2026. US Forests are Increasingly Invaded by Problematic NIS Plants. Forest Ecology & Management 599 (2026) 123281

USDA Animal and Plant Health Inspection Service

APHIS is responsible for preventing intro and spread of pests and invasive plants that harm agric, including forests. APHIS policy guides port inspections carried out by the DHS CBP. APHIS inspects imported live plants.

Introductions of pests and pathogens have continued to occur. APHIS funding has remained steady – which means it is not growing to match the rising threat. At minimum, maintain current levels.

FY2025 enacted            FY26 House                 FY26 Senate

APHIS total                                          $1,148                          $1,146                          $1,168

Plant health subtotal                              $387.5                                                              $388.6

Agric. quarantine                      $35.5                            $35.5                            $35.5

Field crop and rangeland           $12                               $11                               $11.5

Pest detection                           $29                               $28.5                            $29

Methods development               $21.5                            $21.5                            $21.5

Specialty crops                          $206.5                          $216.3                          $208.5

Tree and wood pests                  $59                               $59                               $58.6

Emergency preparedness and response* $44.5                            $44.5                            $44.3

* this fund is apparently for both animal and plant emergencies

Rationale

Already introduced pests threaten the many forest products and services benefitting all Americans. Just 15 of the worst pests threaten 41% of forest biomass in the “lower 48” states – comparable to fire.[1] A significant proportion of the resulting costs are imposed on municipal governments and homeowners. Fifteen years ago, it was estimated[2] that the municipal governments were spending more than $1B / year, primarily on removing and replacing trees on public property killed by these non-native pests. Homeowners faced costs of $1B plus loss of another $1.5B in property value. A more recent study estimated that cities will have to spend $30M per year to remove and replace ~ 1.4M street trees by 2050. Additional trees in parks and on homeowners’ properties also die.[3]

A new pattern has appeared in recent years: more newly-introduced pests are being detected in the Pacific Coast states rather than in the East and Midwest. Two southern California counties are projected to pay $150M – $1B[4] to remove and replace trees killed by invasive shot hole borers. The emerald ash borer threatens 9,000 ash on the streets of Portland, Oregon and millions more in parks and the forested wetlands of Willamette Valley, including in Ankeny National Wildlife Refuge. The Mediterranean oak borer has already killed thousands of oak trees in the San Francisco Bay area; it also threatens urban forests and valued oak savannahs in Oregon.

Additional introductions of highly damaging wood-borers are likely because we continue to receive inadequately treated crates, pallets, and other forms of packaging made of wood. For 20 years, all countries shipping goods to North America must treat their wooden packaging per prescribed protocols. To address this risk, we urge a modest $1M increase in APHIS’ “Tree and Wood Pest” account. We also suggest that the Subcommittee inquire of APHIS what steps it will take to improve compliance with the treatment requirement. You should focus your inquiry on China; wood packaging from this country is three times more likely to harbor a tree-killing pest than the global average.[5]

Other pests—especially plant diseases and sap sucking insects—enter on imported plants. Pathogens introduced recently via this pathway include rapid ohia death in Hawai`i (threatening the species that constitutes 80% of the Islands’ forest biomass) and beech leaf disease (thin a dozen years has spread across much of the East).

All assessments of APHIS’ plant import programs’ effectiveness use data from 2009; at that time, plant imports were more than 100 times more likely to transport pests than was wood packaging.[6] APHIS has amended its regulations several times since 2009. We urge the Subcommittee to call for APHIS to facilitate independent analysis of the efficacy of its current phytosanitary programs in order to understand whether the updated regulations have reduced the risk of additional introductions.

Again, pests introduced via this pathway proliferate and spread – often facilitated by movement of firewood, plants, and outdoor household goods. APHIS’ programs have suffered severe failures to prevent such spread, for example in the cases of the emerald ash borer and sudden oak death. We suggest that the Subcommittee inquire of APHIS what steps it will take to improve containment efforts regarding damaging plant pests, including through collaboration with its state partners.

We ask for small increases to the Pest Detection and Methods Development programs. The first enables prompt detection of newly introduced pests … which is critical to successful pest eradication or containment. The second empowers APHIS to improve essential detection and eradication tools.

The current emergency fund of is far below the level needed to respond when a new pest is discovered. We thank both the House and the Senate for clearly recognizing that these appropriations are inadequate by including in their bills language reiterating the Agriculture Secretary’s power to access funds from other Departmental programs (usually the Commodity Credit Corporation) to respond to emergencies.

[1] Fei, S., R.S. Morin, C.M. Oswalt, and A.M. 2019. Biomass losses resulting from insect and disease invasions in United States forests. PNAS August 27, 2019. Vol. 116 No. 35  17371–17376

[2] 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)

[3] Hudgins, E.J., F.H. Koch, M.J. Ambrose, and B. Leung. 2022. Hotspots of pest-induced US urban tree death, 2020–2050. Journal of Applied Ecology

[4] Jetter, K. A. Hollander, B.E. Nobua-Behrmann, N. Love, S. Lynch, E. Teach, N. Van Dorne, J. Kabashima, and J. Thorne. 2022. Bioeconomic modeling of invasive species management in urban forests: final report.

[5] Haack RA, Hardin JA, Caton BP and Petrice TR (2022) Wood borer detection rates on wood packaging materials entering the United States during different phases of ISPM#15 implementation and regulatory changes. Front. For. Glob. Change 5:1069117. doi: 10.3389/ffgc.2022.1069117

[6] 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

Congressional Committees with Jurisdiction … & how to submit testimony

FUNDING APHIS

House Committee on Appropriations, Subcommittee on Agriculture, Rural Development, Food and Drug Administration, and Related Agencies

Chairman: Andy Harris (R-MD)

Members: Robert Aderholt, David Valadao, John Moolenaar, Dan Newhouse, Julia Letlow, Ben Cline, Ashley Hinson, Scott Franklin

Democrats à Sanford Bishop, Jr., Chellie Pingree, Lauren Underwood, Marie Gluesenkamp Perez, Marcy Kaptur, Debbie Wasserman Schultz

deadline: May 1; email to ag.approp@mail.house.gov

instructions: 5 pages, double-spaced in Times New Roman, 12 Point Font; single-sided; PDF attachment to your email. At top of 1st page, clearly indicate your name, title, & institutional affiliation (if any); In 1st paragraph, clearly state agency, program, & amount of funding in the request

MUST also send Truth in Testimony form here.

Senate Committee on Appropriations, Subcommittee on Agriculture, Rural Development, Food and Drug Administration, and Related Agencies

Chairman: John Hoeven (R-ND)

Members: Republicans à Mitch McConnell, Susan Collins, Jerry Morn, Cindy Hyde-Smith, Deb Fischer, Mike Rounds

Democrats à Jeanne Shaheen, Jeff Merkley, Tammy Baldwin, Martin Heinrich, Gary Peter, Kirsten Gillibrand, Jon Ossof

deadline: not clear; might be 22 May; email to agri@appro.senate.gov

instructions: 4 pages.. At top of 1st page, clearly indicate your name, title, & institutional affiliation; state agency, program, & amount of funding in the request

FUNDING  USFS

House Committee on Appropriations, Subcommittee on Interior, Environment and Related Agencies

Chairman: Mike Simpson (R-WY)

Members: Republicans à Mark Amodei, Guy Reschenthaler, Michael Cloud, Ryan Zinke, Jake Ellzey, Celeste Maloy

Democrats à Chellie Pingree (D-ME), Betty McCollum, Josh Harder, James E. Clyburn

deadline: 22 April; email to IN.Approp@mail.house.gov

instructions: 4 pages, single-spaced in 12 Point Font; single-sided; prefer PDF but other formats OK. At top of 1st page, clearly indicate your name, title, & institutional affiliation (if any); In 1st paragraph, clearly state agency, program, & amount of funding in the request

MUST also send Truth in Testimony form here.

Senate Committee on Appropriations, Subcommittee on Interior, Environment and Related Agencies

Chairman: Lisa Murkowski (R- AK)

Members: Republicans à Mitch McConnell, Shelly Moore Capito, John Hoeven, Deb Fischer, Mike Rounds

Democrats à Jeff Merkley, Chris van Hollen, Martin Heinrich, Tammy Baldwin, Kirsetn Gillibrand, Jon Ossof

deadline: unclear; possibly mid-June; email to int@appro.senate.gov

instructions: 4 pages, single-spaced in Microsoft Word or Word Perfect; do NOT send PDF.  At top of 1st page, clearly indicate your name, title, & institutional affiliation (if any); In 1st paragraph, clearly state agency, program, & amount of funding in the request