plants as pest vectors – Center for Invasive Species Prevention

EEICAT: improved method for assessing bioinvasion impacts

As bioinvasions and their impacts continue to expand globally, managers and decision-makers charged with developing effective management and mitigation strategies urgently need tools that can assess and rank all impacts. These start with impacts on species’ populations … but go much farther, to the assemblage, ecosystem, and abiotic levels. Impacts at the “species and assemblage” level include species extinction (locally or more broadly), changes in species range, assemblage structure, successional patterns, and the soundscape. Impacts at the “ecosystem function” and “abiotic” levels include changes to primary production, food webs, water quality, and nutrient cycles. The analysis also addresses changes that do not affect native biota directly, although they present no examples.

For a decade, scientists studying bioinvasions have used the Environmental Impact Classification for Alien Taxa (EICAT) framework to standardize categorization of species-level impacts. One group that has not used this methodology is experts on tree pests. Why? Does the approach fail to describe the impacts of non-native arthropods and pathogens on tree species and forest ecosystems more broadly? Or is it simply because of academic silos?

Even more important: are the science and practical management of invasive species and forest pests losing valuable insights, resources, policy choices, … because of this schism? Would both groups gain from closer interactions?

In any case, the framework used by many scientists working on “invasive species” is undergoing a revision to better capture cascading and systemic effects from bioinvasion. A group of scientists has created the Extended EICAT (EEICAT) framework. (See the publication reference at the end of this blog to learn the process of development and details of the new system.) The proponents claim that the new system recognizes the functional interdependence of species in ecosystems, which means that alterations in species assemblages inevitably amplify throughout the system. E.g., alterations in physico-chemical characteristics or habitat structure. Impacts can even cross-ecosystem impacts between ecosystems that are often managed separately. An example is a change in the quality, magnitude, and novelty of resource flows between terrestrial and aquatic systems. To address these multifaceted effects, EEICAT integrates 19 impact types into the analysis. The intention is to improve communication about the complex ecological impacts caused by bioinvasions and facilitate prioritization of responses to competing bioinvasions.

While the various outcomes from bioinvasion can be positive or negative for nature and people, the EEICAT does not use value-laden distinctions. These determinations are left to stakeholders, managers, and community members, based on their own perspectives. Instead, it compiles and standardizes information about the measurable changes to species numbers (some decrease, others increase); to ecosystem processes (e.g., nutrient dynamics or hydrological regimes).

EEICAT incorporates the “reversibility concept”, which addresses the potential for a native sp (including individuals, pops, and assemblages), ecosystem function, or abiotic environmental to recover after removal of the bioinvader. The system developers distinguish “naturally reversible changes” and “naturally irreversible changes”. In the former case, the affected spp, ecosystem processes or abiotic conditions are thought likely to return to their original state within 10 years or three generations (whichever is longer) through natural processes or human-assisted actions that do not exceed what is already being done. This does not include reintroductions or restoration efforts that require new efforts. Instances of “naturally irreversible changes” are those in which the affected species, ecosystem functions, or abiotic conditions cannot return to their original state within that timeframe without significant additional human intervention, or even after intense human intervention. The system has reached a different, stable equilibrium. These “permanent” changes are the result of one or more species’ global extinction, or persistent environmental alterations, e.g., soil modification, altered hydrology, or irreversible changes in nutrient cycling.

The proponents assert that EEICAT allows multiple impacts reported in a single study to be classified independently at each impact level. Furthermore, the EEICAT analysis does not require extensive research on the assessed species or understanding of the mechanisms through which the invasive species affects native species or the environment. EEICAT framework is applicable to any amount of info available in each study. It also explicitly assesses the adequacy / reliability of evidence [data, methods, approach] used in studies of bioinvasions that are included in the analysis.

EEICAT framework enables researchers to evaluate how “ecosystem engineer” species influence key ecological functions by explicitly accounting for changes to ecosystem processes, e.g., nutrient dynamics or hydrological regimes. For example introduced bivalves increase water clarity in certain systems, triggering cascading effects on biodiversity and ecosystem functions.

The EEICAT framework also allows separation of the mechanisms of impact vs. attribution of impact. For example, when a non-native plant species alters nutrient availability, thereby changing the microbial community, EEICAT assigns separate impact categories to the two impacts.

Regarding cross-ecosystem effects, the proponents cite rats on islands. Their predation suppresses seabird pops; reduced guano alters the nutrient dynamics of adjacent coral reef ecosystems. Thus assign impact categories not only to the changes in nutrients, but also to ecological functioning. This provides a more comprehensive view of interconnected effects.

Proponents of the proposed new framework assert that the fundamental distinction between EEICAT and the earlier EICAT is that the earlier assessment is “species-based”, whereas the new one is “impact-based”. It is broader because it focuses on specific combinations of invading species plus the affected systems. It is better able, they assert, to account for contrasting impacts in different invasions.

EEICAT can be applied to any invasion event (i.e., a specific combination of invasive species, recipient system, and context). It broadens the range of evidence that can be integrated into the assessment. Decision-makers benefit from access to more information. The information can also be provided in more easily understood form through two visualization tools:

An “invasive species profile” aggregates all recorded impacts caused by a single invading species. This facilitates clear communication of the bioinvasion’s impact severity to managers and stakeholders, plus how those impacts vary by context.
An “invaded ecosystem profile” compiles impacts from different species to a site or location. This is particularly useful for synthetic analyses (e.g., meta-analyses), evidence syntheses, and manager assessments.

Resulting profiles can help stakeholders prioritize species or ecosystems for responses.

https://www.dontmovefirewood.org/pest_pathogen/phytophthora-root-rot-html/to are ants. No disease agent is discussed or even named. This gap is surprising given the devastating and geographically extensive impacts of e.g., avian malaria, chitrid fungi (Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans) on amphibians, and Phytophthora cinnamomi on the flora of western Australia.

One example in Table 3 pertains to native Hawaiian forests. The underlying study analyzed changes in ecosystem functions caused by the invasive nitrogen-fixing tree Falcataria moluccana. The EEICAT proponents say their analysis of this study would supports more informed decisions in conservation planning and ecosystem management. Indeed, the principal author of the underlying study has recently published a suggested method to manage the Falcataria moluccana invasions by replacing these trees with either native species or valued crops under an agroforestry program. Neither of the articles mentions that exactly this same area (the Puna District on the “Big Island) has suffered widespread death of the native tree ʻōhiʻa lehua (Metrosideros polymorpha) as a result of the invasive disease rapid ʻōhiʻa death (ROD). The more recent article does address the fact that native plant species are extremely rare in this region.

Would integrating studies of tree-killing arthropods and pathogens into the EEICAT system provide benefits? First, let’s consider analytical methodology. Many analyses of forest pests’ impacts already discuss at least some of the wider ecological (and economic) outcomes. (To explor this, visit www.dontmovefirewood.org and read some of the species profiles under the “invasive species” tab.) Would comparing these findings to an EEICAT analysis confirm the proposed methodology? Or would it instead suggest needed adaptations? In either case, the results should improve scientists’ work.

Second, would the science and practice of managing invasive species be strengthened by bridging the differences in methods and terminology between those focused on plants and vertebrates and those focused on tree-killing invertebrates and microbes? Would greater unity result in more attention to bioinvaders from policy-makers and/or conservation practitioners and advocates? Especially since (nearly) all the major forest pest invasions would qualify as “naturally irreversible changes” or even “permanent”: the affected species, ecosystem processes or abiotic conditions are thought unlikely to return to their original state within 10 years or 3 generations (whichever is longer) in the absence of intense human-assisted actions. If joining forces might bring about greater societal efforts, is the EEICAT methodology a promising tool to achieve this goal?

Finally, would applying the EEICAT system improve the analyses of tree-pest impacts? Would this approach result in incorporation of types of effects that would otherwise be missed – either often or in specific cases? Are there relationships among forest species, or between species and ecological functions, that might be discovered? Might preparation of “invaded ecosystem profiles” that include bioinvaders from earthworms to canopy foliage feeders provide an informative perspectives that is now lacking?

SOURCE

Carneiro, L., Pincheira-Donoso, D., Leroy, B., Bertolino, S., Camacho-Cervantes, M., Cuthbert, R.N., et al. (2026) Expanding invasive species impact assessments to the ecosystem level with EEICAT. PLoS Biol 24(3): e3003665. https://doi.org/10.1371/journal.pbio.3003665

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/

Is this a way to overcome difficulties detecting invasive pathogens? Is APHIS applying these ideas?

SOD-infected rhododendron in a nursery; photo by Jennifer Parke, ODF

A group of scientists (See Khusnitdinova et al., 2026; full reference at the end of this blog.) contend that landscape interfaces—e.g., crop–forest edges, riparian zones, abandoned agricultural fields and orchards, and nursery–wildland transitions—are active zones of pathogen exchange. Biological and abiotic vectors collectively move pathogens from crops to wild plants, and vice versa. These exchanges create conditions speed up the evolution of pathogen aggressiveness and dispersal traits and promote the selection of generalist pathogen lineages capable of infecting both cultivated and wild hosts. In this way, crop-natural ecotones become not just passive transition zones but centers of adaptation.

The stronger or novel pathogens don’t stay in the specific local area; they are spread by a variety of human activities. Establishing large monocultures of crops and simplifying biological diversity at the landscape level boost inoculum production, limit host genetic diversity, and diminish natural regulation. Pathogens present in irrigation water can be spread during floods. Improperly sanitized green waste and compost can harbor viable oomycete propagules. Foot traffic and heavy equipment can move contaminated soil. Movement of infested plants for planting can transport the disease to a different continent. One example cited by Khusnitdinova et al. (2026) is the spread of numerous Phytophthora spp. from nurseries to forests and shrublands. A second example is rapid ʻōhiʻa death. They say it demonstrates that 1) a combination of human movement, forestry activities, and animal vectors can enable rapid local and landscape-scale spread; and 2) management measures (biobarriers, access control, restriction of animal movements, and phytosanitary inspection of planting material) can curtail that spread.

Meanwhile, the changing climate is causing shifts in the latitudinal and elevational distribution of plants and their associates; changing reproduction rates and latent periods; altering ranges and connectivity; and affecting disease incidence and severity. The direction is not always predictable; while drought or heat might reduce fungal and oomycete epidemics, the same conditions increase host stress and so might worsen disease outcomes.

Plant health scientists can use these concentrated geographic areas to focus plant disease surveillance. By integrating molecular and genomic tools with remote sensing and Geographic Information System (GIS)-based monitoring, plant health agencies can more quickly detect newly emerging diseases and implement effective action to counter the threat.

However, Khusnitdinova et al. (2026) warn that surveillance employing these technological advances can reduce the risk that a pathogen will “spill over” from an anthropogenic to a natural ecosystem or vice versa only if pertinent sectors are transformed. Yes, they need resources: funding, staff, facilities. Also required is unification – or at least coordination. Khusnitdinova et al. (2026) advocate abandoning the compartmentalization that currently separatesforest health studies from invasive-plant and infectious-disease ecology studies. Instead, agencies should consider managed and natural systems together. They should conduct joint surveillance programs, share data standards, and coordinate management of the transition zones. In other words, apply a “One Health” landscape-based approach to the entire landscape.

Khusnitdinova et al. (2026) add that implementing such combined surveillance programs is especially vital in biodiversity-rich regions which have limited monitoring capacity. Might I suggest Hawai’i?

ohia trees killed by ROD; photo by J.B. Friday, UH

Other facts that challenge traditional phytosanitary practices

Khusnitdinova et al. (2026) provide strong evidence that pathogens change – sometimes quickly. Is the current regulatory system sufficiently flexible and agile to effectively address these developments?

First, pathogens’ host range is not fixed. Instead, it is a trait that changes quickly under the influence of alterations in effector repertoires, plant immunity genes, and environmental conditions (including those driven by human actions). Even small genetic changes—such as mutations, gene losses or gains, or horizontal gene transfers—can enable pathogens to infect new hosts or weaken previous infection barriers. They suggest that plant pathogens with broad host ranges, e.g., Phytophthora cinnamomi, can easily move between hosts in agricultural plantings, ornamental landscapes, and semi-natural vegetation within a relatively small region. Such frequent spillovers maintain inoculum in landscape mosaics and complicating eradication or containment efforts.

Khusnitdinova et al. (2026) note that host-range expansions have especially long-term consequence in forest ecosystems, where loss of a single tree species can change understory makeup, light and moisture patterns, related fungi and invertebrate communities, and ultimately, landscape diversity and function. They cite chestnut blight and sudden oak death in North America and ash dieback in Europe as examples.

In addition, Khusnitdinova et al. (2026) maintain that genetic recombination is now recognized as a fundamental driver of innovation in plant pathogen populations. Table 2 of their publication lists pathogens exhibiting well-documented and experimentally confirmed cases of recombination, hybridization, or other forms of genome exchange. Forest-related examples include several Phytophthora hybrids and the ash decline fungus, Hymenoscyphus fraxineus.

Phytophthora dieback in Western Australia

Khusnitdinova et al. (2026) add their voices to a growing chorus decrying a global forest health crisis. They say that repeated pathogen introductions—often via trade in plants and wood—have shifted many temperate and boreal forests into states characterized by higher tree mortality, increased dominance of opportunistic or disturbance-adapted species, and reduced functional diversity. These changes lead to reduced resistance [defined as the capacity to limit damage during a new outbreak] and resilience [defined as the speed and trajectory of post-disturbance regeneration and ecosystem reorganization]. They note that increasing tree species diversity is one of the few management interventions that succeeds in strengthening both forest resistance and resilience to pathogens—by decreasing host density for specialist pathogens and reducing continuous “fuel” for epidemics.

One step toward improving scientific understanding on the scale they advocate, in their view, is the European Holistic Management of Emerging Forest Pests and Diseases (HOMED) effort. HOMED combines plant pathology, forest ecology, and biosecurity. The emphasis is on early detection, risk assessment, and management of human-mediated pathways, incl plant trade and nursery systems. The initiative aims to limit pathogen establishment and spread while strengthening forest resistance and resilience under global change. Participants also try to provide practical solutions for stakeholders to manage emerging native and non-native pests and pathogens threatening European trees not only in forests, but also in nurseries, urban and rural areas.

I am inspired by the proposals in Khusnitdinova et al. (2026). In hopes that USDA will explore how to implement them, I presented a poster presentation at the annual USDA Research Forum on Invasive Species. In that poster I suggested that these ideas complement USDA Secretary Rollins’ Memorandum on departmental research priorities. The need for research to clarify scientific puzzles is particularly acute regarding tree-killing pathogens nematodes, etc.

I suggested prioritizing research on the following issues:

Setting up intensive monitoring programs targetting the agriculture/natural system interfaces, as recommended by Khusnitdinova et al. (2025). These authors describe useful technologies in molecular diagnostics, genomic surveillance, environmental DNA, and remote sensing to detect fungi, oomycetes, rusts, bacteria, and viruses. Kantor et al. (2025) define techniques applicable for nematodes.
Rapid analysis of potentially invasive species and their pathways of entry revealed by “early warning” systems [e.g., APHIS’ “PestLens” website; “door knocker” introductions; academic studies; and “unimportant” species introduced to the U.S. (e.g., Leptosillia pistaciae in California)].
Exploring ways (in addition to those suggested by Khusnitdinova et al. 2025) to shorten the time lag between introduction of a pathogen and its detection.
Incorporating into risk analyses information from sentinel garden program. Fund expansion of data collection and analysis to address asymptomatic plants, sampling techniques, and seasonality, as outlined by Drs. Eliana Torres Bedoya and Enrico Bonello (at the 2025 USDA Research Forum) and Raffa et al. (2023).

Over a somewhat longer-term, I suggested that research address these topics:

Find techniques to speed up determination of disease causal agents – which often remain obscure for years or decades. The International Plant Protection Convention (IPPC) link requires countries to name the causal agent before regulating disease hosts and vectors.
Determine which components of a “systems approach” are most effective against each type of pathogen – fungi, oomycetes, rusts, bacteria, viruses, nematodes, etc.
With state counterparts, explore ways to better curtail domestic spread of organisms once they have established in the United States.
Integrate socio-economic drivers of pest introductions into studies. E.g., why do some organisms suddenly spread to numerous countries over a period of a few years?
Greatly expand efforts (in house and by collaborators) to breed trees resistant to established and newly detected pathogens.
Increase research supporting biocontrol.

As I have frequently complained in the past, the international phytosanitary system has failed to protect Earth’s forests and other natural ecosystems from non-native plant pests (or invasive plants). This failure has been documented by Weed, Ayres, and Hicke (2013), Fei et al. (2019), Quirion et al. (2021) for North America; and Gougherty (2023), Wu (2023), Sitzia et al. (2021), Martinac et al. (2025) and Khusnitdinova et al. (2025) from a global perspective.

Challenges:

Most microorganisms are unknown to science – “unknown unknowns”.
Scientists usually cannot predict the impact of known micro-organisms on new hosts under novel environmental conditions.
The World Trade Organization’s SPS Agreement and the International Plant Protection Convention (IPPC) demand unachievable levels of specificity re: a potential pest’s impact.
Most tree-killing pathogens are detected after they have entered the forest.
Agencies assign a low priority to protecting natural ecosystems from bioinvasion.
Resources (funds, staffing, etc.) are unreliable for agencies carrying out the full range of efforts, from assessing various risks to restoring pest-resistant trees to the forest.

SOURCES

Fei, S., R.S. Morin, C.M. Oswalt, & A.M. 2019. Biomass losses resulting from insect & disease invasions in United States forests

Gougherty, A.V. (2023) Emerging tree diseases are accumulating rapidly in the native & non-native ranges of Holarctic trees. NeoBiota 87: 143–160. https://doi.org/10.3897/neobiota.87.103525

Kantor, C., Teixeira, M., Kantor, M., and Gleason, C. 2025. Tiny Invaders, Big Trouble: Emerging Nematode Threats in the United States. Phytopathology 2025 115:587-595 https://doi.org/10.1094/PHYTO-09.-24-0290-IA

Khusnitdinova, M., V. Kostyukov, G. Nizamdinova, A. Pozharskiy, Y. Kydyrbayev and D. Gritsenko. 2026. Cross-Ecosystem Transmission of Pathogens from Crops to Natural Vegetation. Forests 2026, 17, 76

Martinac, M-L., F. Ningre, A. Dowkiw, N.Le Goff, B. Marcais. 2025. High host density favour ash dieback Preprint Plant Pathology

Quirion BR, Domke GM, Walters BF, Lovett GM, Fargione JE, Greenwood L, Serbesoff-King K, Randall JM & Fei S (2021) Insect and Disease Disturbances Correlate With Reduced Carbon Sequestration in Forests of the Contiguous United States. Front. For. Glob. Change 4:716582. [Volume 4 | Article 716582] doi: 10.3389/ffgc.2021.716582

Sitzia, T., T. Campagnaro, G. Brundu, M. Faccoli, A. Santini & B.L. Webber. 2021. Routledge Handbook of Biosecurity & invasive species. Chapter 7. Forest Ecosystems. ISBN 9780367763213

Weed, A.S., M.P. Ayers, J.A. Hicke. 2013. Consequences of CC for biotic disturbances in North American forests. Ecological Monographs, 83(4), 2013, pp. 441–470

Wu, H. 2023/24. Modelling Tree Mortality Caused by Ash Dieback in a Changing World: A Complexity-based Approach MSc/MPhil Dissertation Submitted August 12, 2024. School of Geography & the Enviro, Oxford University

Posted by Faith Campbell

Or https://fadingforests.org/

Pest Threats to Plantations: Will At-Risk Countries Demand Improvements to IPPC?

pines in a plantation in Argentina killed by *Sirex noctilio*; photo by J. Villacide

A decade ago, Payn et al. (2015) compiled studies from around the globe to evaluate threats to widespread tree plantations. At that time, they said climate change posed the greatest threat to plantation forestry globally, in the forms of storm and flood damage and simultaneous warming and drying trends with extreme temperatures.

Still, the authors warned that forest health would be an increasingly important constraint to plantation productivity. They were optimistic, however, that modern breeding and other technologies could offset losses.

What is the current situation? The countries that depend on these plantations for fiber production are not demanding that leaders of the international phytosanitary structure build a more effective system to protect their investments. Instead, individual scientists struggle to better understand threats. Mostly, they propose expanded research.

Economic Importance of these Species

Eucalypts

“Eucalypts” comprises three genera in the family Myrtaceae: Angophora, Corymbia and Eucalyptus. These include more than 700 tree species native primarily to Australia. A few species are native to Indonesia, New Guinea and the Philippines (Paine et al. 2011; Crous et al. 2019). Some of these species have been extensively planted outside their native ranges for more than 100 years. These plantations have expanded rapidly in recent decades, especially in Southeast Asia and the Southern Hemisphere (Crous et al. 2019). Eucalypts are now the most widely planted hardwood timber in the world (Paine et al. 2011).

Eucalypt plantation in Brazil; photo by Jonathan Wilken via Wikimedia

Eucalypts’ popularity has been driven chiefly by their rapid growth; short rotation times including through coppicing; and adaptability to a very wide variety of sites and climatic conditions (Paine et al. 2011; Crous et al. 2019). Also, these trees are an important source of the short-fiber pulp required for production of high-quality paper used in modern office copiers and printers (Paine et al. 2011). Plantations are increasing even in Australia, where harvesting of native forests is increasingly being restricted (Paine et al. 2011).

Pines

Pines – a genus restricted naturally to the Northern Hemisphere – is second in global popularity. South America hosts 4.6 million hectares of pine plantations (Lantschner and Villacide 2025). South America is more dependent on forestry plantations for wood production than any other region. In 2012, 88% of its industrial roundwood was produced by non-native plantations. This far exceeded the global proportion of approximately 19%.

These intensively managed plantations have enabled Brazil and Chile to become “planted forest powerhouses.” Uruguay and, more slowly, Argentina are following the same path (Payn et al. 2015).

Documentation of the Damage

Euclaypts

The highly diverse eucalypts host an even greater diversity of fungi. As of 30 years ago, scientists were aware of more than 500 species of just one type, the leaf-infecting fungi. Additional fungi are associated with seeds, capsules, twigs, branches, and stems. Little is known about the vast majority of these fungi. Even species considered causal agents of important diseases have not yet been confirmed using Koch’s Postulates. Areas of origin for most is also unknown (Crous et al. 2019).

Crous et al. (2019) compiled information on 110 genera of fungi found on eucalypt foliage. Some genera include well-recognized primary pathogens. They name Austropuccinia and Calonectria, Coniella, Elsinoe, Pseudocercospora, Quambalaria and Teratosphaeria. Other genera are thought to include species that are opportunists that develop on stressed or dying tissues. Many other leaf fungi are putative pathogens, but unstudied. Additional fungi cause vascular wilts (e.g. Ceratocystidaceae), stem canker diseases (Cryphonectriaceae, Botryosphaeriaceae) and root diseases (e.g. Armillaria, Ganoderma) of eucalypts.

Crous et al. (2019) state that the rust Austropuccinia psidii is one of the most damaging of the foliage fungal pathogens. They consider it to be a greater threat to eucalypt plantations outside the trees’ native ranges. (The Myrtaceous species in Australia most damaged by A. psidii are in other genera.)

Two families of leaf fungi – Mycosphaerellaceae and Teratosphaeriaceae – include species that cause serious diseases. Pérez, et al. report a study in plantation in Uruguay that detected six new species. They also discovered new hosts for some known species. (Such initial detections of new fungal species in out-of-native-range plantations is a usual occurrence.)

Over the 100-year history of planting eucalyptus outside Australasia, dozens of leaf pathogens have been transported to novel regions. Crous et al. 2019 report the wide geographic breadth of many of these introductions. For example, Mycosphaerella heimii is crippling plantation forestry in five global regions – South America (Brazil and Venezuela); Asia (Indonesia and Thailand); Africa (Madagascar), Europe (Portugal); and in its presumably native Australia. A second species, M. marksii, has a similarly wide introduced range: Portugal, China and Indonesia, South Africa, Ethiopia, and Uruguay. Pérez et al. calls Mycosphaerella leaf diseases one of the most important impediments to Eucalyptus plantation forestry in Uruguay.

Although Crous et al. do not provide dates of detection, it appears that many of these leaf pathogens were introduced outside Australasia before the mid-990s, when the World Trade Organization (WTO) and International Plant Protection Convention (IPPC) came into force. Together, these agreements govern what actions phytosanitary officials may take to curtail international movement of plant pests. (To see my critique of the WTO/IPPC system, visit here.) The possible exception might be Kirramyces gauchensis, a well-known pathogen of Eucalyptus grandis in South America (Argentina and Uruguay), Hawai`i, and Africa (Uganda and Ethiopia) (Pérez, et al. 2009). Crous et al. (2019) expect another genus, Quambalaria species, to become a threat to eucalypt plantation forestry globally in the future.

*Phoracantha semipunctata*; photo by Umo Schmidt via Flickr

Arthropod pests have also been spread to many Eucalyptus-growing regions in North and South America, Europe and Africa since the 1980s. Some species have colonized virtually all eucalypt-growing regions, e.g., Phoracantha semipunctata. Some have – so far – appeared on only one continent.

In an effort to determine how many of these introductions have occurred after adoption of the WTO/ IPPC system, I Googled the species named by Paine et al. (2011). I used the year 2000 as the cutoff date, to allow for detection lag. Among the insect species that fit this criterion are a lerp psyllid, a leaf beetle, and two gall wasps detected in North America; a true bug, two galling insects, and a leaf beetle in South Africa; and three psyllids in Europe.

Asia stands out as having very few introduced Australian insects plaguing eucalyptus plantations. Only one insect of Australian origin is causing significant damage in this region, Leptocybe invasa. It was detected after 2000, so it might have been introduced under the WTO/IPPC regime. Many widespread species, e.g., Phoracantha semipunctata, are notably absent. Instead, large numbers of endemic insects use these trees. This contrasts with the situation in the Southern Hemisphere, where few of the numerous native insects have shifted onto eucalypts.

New Zealand has detected only two new species of Australian origin since 1999 — two psyllids. This is despite the two nations’ proximity, the large volume of trade that passes between them, and the likelihood that at least some small sap-suckers might be introduced via aerial dispersal. New Zealand is famous for its strict phytosanitary (and sanitary) policies and programs.

Eucalyptus plantation in Kwa-Zulu, South Africa

Plantations’ vulnerability has been increased by expanding reliance on clonal, artificially-induced hybridization. Developers’ goals – and initial results – are enhanced adaptation to specific environments, desired fiber characteristics, and hybrid vigor. However, these vast areas planted in genetically identical trees are sitting ducks. An insect or pathogen that overcomes the host’s defenses can spread rapidly across the entire planting.

These hybrids also can act as “bridges,” facilitating spread of fungi to formerly resistant host species. Crous et al. (2019) fear that this process will undermine resistance in Eucalyptus pellita to the pathogen Teratosphaeria destructans. Plantations in Southeast Asia and South Africa now comprise hybrids between this resistant species and the highly susceptible Eucalyptus brassiana.

Pines

As with the eucalypts, the intensively managed pine plantations are comprised of fast-growing exotic species, all at the same developmental stage, and with minimal genetic diversity, planted to maximize wood production. These practices again lead to biological homogenization and reduced resilience to pests (Villacide and Fuetealba, 2025)

In the Southern Hemisphere, Sirex noctilio has become the most significant economic pest of Pinus species. These attacks can cause up to 80% mortality. Several other Sirex species have also been introduced, all apparently in the 1980s or earlier (Wilcken et al., 2025) – before adoption of the current international phytosanitary regime. However, in 2023, a new species, Sirex obesus, was discovered causing tree mortality in pine plantations in southeastern Brazil. This species is indigenous to the United States and Mexico.

Stazione et al. (2026) discuss two other non-native pine pests that established recently in South America.

Analysis of mitochondrial DNA of Orthotomicus erosus points to a western Eurasian lineage. The low genetic diversity of the introduced population in Argentina and Uruguay suggests a single or limited introduction event followed by regional spread.

The source region of Cyrtogenius luteus is more difficult to determine but is probably somewhere in China. The higher haplotype diversity might reflect multiple introductions. Again, shared haplotypes between Argentina and Uruguay countries indicates a contiguous regional spread, possibly driven by extensive pine plantations & intra-regional trade (Stazione et al. 2026)

Policy Aspects

Some scientists express concern about the failure of international phytosanitary measures. But are their countries speaking up in regulatory bodies, especially the International Plant Protection Convention?

Studies by Crous et al. (2019) and Pérez et al. (2009) clearly show that pathogens from Australia continue to be transported to regions where eucalypt plantations are grown. This happens despite most of the movement of genetic material being in the form of seeds – which should be less likely to transport pathogens than trade in plants. Pérez et al. (2009) explicitly raise concerns about the effectiveness of current quarantine procedures. Crous et al. (2019) state that quarantines continue to fail in many parts of the world.

Burgess and Wingfield (2017) list pathogens that have spread widely since the beginning of the 21st Century: Austropuccinia psidii, Calonectria (= Cylindrocladium) eudonaviculata (=Cylindrocladium buxicola), Ceratocystis lukuohia and C. huliohia introduced to Hawai`i. I add that insect-vectored diseases such as Euwallacea species carryingFusarium fungi have also experienced a burst of introductions around the globe since 2000.

Crous et al. (2019) attribute this failure partially to the enormous difficulty of applying effective quarantine to the huge volumes of planting material traded globally. Another factor is undoubtedly the poor understanding of microbial species, their pathogenicity, hosts, pathways of spread, even taxonomies. Some genera cannot be grown in culture.

Furthermore, pathogens’ impacts vary, possibly due to environmental conditions of the location or differing virulence on different hosts. Finally, with so many fungi and so little knowledge, it is difficult to separate true disease agents from multiple secondary infections.

Crous et al. (2019) express the hope that increased recognition of the importance of pathogens, along with improved detection and identification tools, will clarify patterns of spread. But is that enough? Are there no policy changes needed?

Crous et al. (2019) also warn us about additional pathways for spreading pathogens. Some potential pathogens of eucalypts have been moved on plants of other, related genera. Furthermore, Botryosphaeriaceae have been detected in the skins of mangoes (Mangifera indica) and avocados (Persea americana). Both of these fruits move globally in large volumes.

mangoes; photo by Obsidian Soul via Wikimedia

Regarding insects, Paine et al. (2011) focus on a concern that species native to the plantation countries and generalist herbivores from other parts of world will invade Australia and threaten eualypts in their native ranges. See other blog They also call for research to understand international pathways, develop detection methods, improve understanding of patterns of host suitability, susceptibility, and selection.

Villacide and Fuetealba (2025) note that while the introductory pathway for that new species, Sirex obesus, has not been determined, they suspect it might have been wood packaging materials. Villacide and another colleague (Lantschner and Villacide 2025) suggest an initial step would be for Argentina and other countries in the region to negotiate with Brazil to adopt more protective protocols governing trade in wood products, including wood packaging.

I have repeatedly advocated strengthening regulation of wood packaging. Such measures could improve protection of Earth’s forests from pests that use a well-documented high-risk introductory pathway. To see my arguments and underlying data, scoll down below the “archives” to “Categories” and click on “wood packaging”.

SOURCES

Burgess, T.I. and M.J. Wingfield. 2017. Pathogens on the Move: A 100-Year Global Experiment with Planted Eucalypts. Bioscience. Volume 67, Issue 1, January 2017. https://doi.org/10.1093/biosci/biw146

Crous, P.W., M.J. Wingfield, R. Cheewangkoon, A.J. Carnegie, T.I. Burgess, B.A. Summerell, J. Edwards, P.W.J. Taylor, and J.Z. Groenewald. 2019. Folia pathogens o eucalypts. Studies in Mycology 94:125-298 (2019).

Lantschner, V. and J. Villacide. 2025. Invasion Potential of the Recently Established Woodwasp Sirex obesus. Neotropical Entomology. (2025) 54:117 https://doi.org/10.1007/s13744-025-01347-6

Paine, T.D., M.J. Steinbauer, and S.A. Lawson. 2011. Native and Exotic Pests of Eucalyptus: A Worldwide Perspective. Annu. Rev. Entomol. 2011. 56:181-201

Payn, T., J-M. Carnus, P. Freer-Smith, M. Kimberley, W. Kollert, S. Liu, C. Orazio, L. Rodriguez, L. Neves Silva, M.J. Wingfield. 2015. Changes in planted forests and future global implications. Forest Ecology and Management 352 (2015)

Pérez,, C.A., M.J. Wingfield, N.A. Altier, and R.A. Blanchette. 2009. Mycosphaerellaceae and Teratosphaeriaceae associated with Eucalyptus leaf diseases and stem cankers in Uruguay For. Path. 39 (2009) 349–360 doi: 10.1111/j.1439-0329.2009.00598.x www3.interscience.wiley.com

Stazione, L., Soliani, C., Cognato, A. et al. Reconstructing the invasion history of the bark beetles Orthotomicus erosus & Cyrtogenius luteus (Coleoptera, Curculionidae, Scolytinae) in South America. Biol Invasions 28, 49 (2026). https://doi.org/10.1007/s10530-026-03779-6

Villacide, J. and A. Fuetealba. 2025. Pests in plantations: Challenging traditional productive paradigms in the Southern Cone of America. Forest Ecology and Management 597 (2025) 123127

Wilcken, C.F., T.A. da Mota, C.H. de Oliveir, V.R. de Carvalho, L.A. Benso, J.A. Gabia, S.R.S. Wilcken, E.L. Furtado, N.M. Schiff, M.B. de Camargo, M.F. Ribeiro. 2025. Sirex obesus (Hymenoptera: Siricidae) as invasive pest in pine plantations in Brazil. Scientific Reports. 2025. 15:22522 https://doi.org/10.1038/541598-025-06418-7

Posted by Faith Campbell

https://fadingforests.org

Threat to Native Myrtaceae in South America

*Blepharocalyx salicifolius –* a tree in the Myrtaceae native to South America on which found symptoms similar to those caused by Mycosphaerellaceae or Teratosphaeriaceae; photo by Pablo di Flores via Wikimedia

Pests that have followed their hosts to plantations outside the trees’ native ranges might threaten native plants in their new, introduced ranges. That is, the countries where the plantations are located.

Eucalypts

Eucalypts are now the most widely planted hardwood timber taxon in the world (Paine et al 2011). The 700 – 800 species in the three genera considered “eucalypts” (Angophora, Corymbia, and Eucalyptus) host a highly diverse fungal community — more than 500 species have been identified of just one type, leaf-infecting fungi (Crous et al. 2019).

As I described in a related blog, link dozens of leaf pathogens have been transported to countries hosting eucalypt plantations. Among them, two families – Mycosphaerellaceae and Teratosphaeriaceae – are prominent in both numbers of introductions and potential to cause serious diseases.

Pérez et al. (2009) reported that a relatively large number of Mycosphaerellaceae and Teratosphaeriaceae are found on Eucalyptusin Uruguay. The authors cite one troubling case of host shifting: Mycosphaerella lateralis is causing leaf disease on a Musa cultivar (banana!) which is not in the Myrtaceae.

A follow-up study by the same authors (Pérez et al. 2013) surveyed several native forests, paying special attention to those located close to Eucalyptus plantations. They found five species belonging to the Mycosphaerellaceae and Teratosphaeriaceae clades on native Myrtaceous trees; three of these had previously been reported on Eucalyptus in Uruguay. Those occurring on both Eucalyptus and native Myrtaceae included Pallidocercospora heimii, Pseudocercospora norchiensis, and Teratosphaeria aurantia. A fourth species, Mycosphaerella yunnanensis, not previously recorded in Uruguay, was found on the leaves of two native Myrtaceous hosts. Pérez et al. (2013) believe circumstances indicate that all these fungi have been introduced. They warn that these apparent jumps to new hosts have the potential to result in serious disease problems and they should be carefully monitored. This finding is more than a decade old; I have not found a more recent report.

On the global level, Pérez et al. (2013) report, at least 23 species of Mycosphaerellaceae and Teratosphaeriaceae have been found on non-Eucalyptus species in the Myrtaceae. These hosts are in several plant orders, including Myrtales, Proteales, Fabaes and Apiales. The authors express “considerable concern” about the apparent ease of movement in these fungi between hosts. I have been unable to learn more details about these introductions.

Arthropod pests have also been spread to many Eucalyptus-growing regions in North and South America, Europe, and Africa since the 1980s – but not to Asia or New Zealand (Paine et al. 2011). blog

*Myrrhinium atropurpureum* – another South American plant in the Myrtaceae on which symptoms found; photo by Prof. Atilio L, Botanical Garden of Uruguay

Pines

Pines – a genus restricted naturally to the Northern Hemisphere – is second in popularity for intensively managed plantations. South America has 4.6 million hectares of pine plantations (Lantschner and Villacide 2025). Most are in Brazil, Chile, Uruguay, and Argentina (Payn et al. 2015).

*Cinara cupressi;* photo by LBM via Wikimedia

As I reported in an earlier blog, some of the insect pests that followed pines to South America have entered native forests. The most alarming of which I am aware is the aphid Cinara cupressi. It attacks the native conifer Austrocedrus chilensis, which forms pure and mixed stands with southern hemisphere beech (Nothofagus spp.) across approximately 160,000 hectares (Villacide and Fuetealba 2025). Cordilleran cypress is also under attack by the oomycete Phytophthora austrocedri, an oomycete of unknown origin.

Some scientists express concern about phytosanitary measures … but are their countries speaking up in meetings of the International Plant Protection Convention?

Studies by Crous et al. and Pérez et al. clearly show that pathogens from Australia continue to be transported to regions where eucalypt plantations are grown – despite the fact that most of the movement of tree genetic material is in the form of seeds – which should be less likely to transport pathogens than trade in plants. Pérez et al. (2009) explicitly raise concerns about the effectiveness of current quarantine procedures. Crous et al. (2019) state that the quarantines continue to fail in many parts of the world.

See my critique of the international phytosanitary system under the IPPC by visiting the Fading Forest II report (see link below) and reading other blogs under the categories “invasive species policy” and “plants as vectors of pests”.

SOURCES

Crous, P.W., M.J. Wingfield, R. Cheewangkoon, A.J. Carnegie, T.I. Burgess, B.A. Summerell, J. Edwards, P.W.J. Taylor, and J.Z. Groenewald. 2019. Foliar pathogens of eucalypts. Studies in Mycology 94:125-298 (2019)

Lantschner, V. and J. Villacide. 2025. Invasion Potential of the Recently Established Woodwasp Sirex obesus. Neotropical Entomology. (2025) 54:117 https://doi.org/10.1007/s13744-025-01347-6

Paine, T.D., M.J. Steinbauer, and S.A. Lawson. 2011. Native & Exotic Pests of Eucalyptus: A Worldwide Perspective. Annu. Rev. Entomol. 2011. 56:181-201

Payn, T., J-M. Carnus, P. Freer-Smith, M. Kimberley, W. Kollert, S. Liu, C. Orazio, L. Rodriguez, L. Neves Silva, M.J. Wingfield. 2015. Changes in planted forests & future global implications. Forest Ecology and Management 352 (2015)

Pérez, C.A., M.J. Wingfield, N.A. Altier, and R.A. Blanchette. 2009. Mycosphaerellaceae & Teratosphaeriaceae associated with Eucalyptus leaf diseases & stem cankers in Uruguay For. Path. 39 (2009) 349–360 doi: 10.1111/j.1439-0329.2009.00598.x www3.interscience.wiley.com

Pérez, C.A., M.J. Wingfield, N. Altier, and R.A. Blanchette. 2013. Species of Mycosphaerellaceae and Teratosphaeriaceae on native Myrtaceae in Uruguay: evidence of fungal host jumps. Fungal Biology Volume 117, Issue 2, February 2013.

Villacide, J. and A. Fuetealba. 2025. Pests in plantations: Challenging traditional productive paradigms in the Southern Cone of America. Forest Ecology and Management 597 (2025) 123127

Posted by Faith Campbell

https://fadingforests.org

Pest Threats to Eucalypts and Australia

*Chilecomadia valdiviana* – one of the South American moths that attack Eucalyptus; photo by Natural History Museum of London via Wikimedia

Fifteen years ago, Paine, Steinbauer, and Lawson (2011) worried that insects in South America, Africa, Asia, and Europe that adapt to attacking Eucayptus trees planted there might be introduced to Australasia and threaten the genus in its native range. Their analysis applies to species in all three genera considered to be “eucalypts” — Angophora, Corymbia and Eucalyptus.

Some insects native to those continents have made this host shift already. Paine, Steinbauer, and Lawson reported that such host switching was especially prevalent among lepidopterans. They name several from Brazil, the Chilean cossid moth, Chilecomadia valdiviana, and southern African Coryphodema tristis. In their view, Brazilian eucalypt plantations’ proximity to native vegetation facilitates host-switching. Still, at that time they thought that there were no established pathways for introduction of the South American moths to Australia.

Host-switching is exceptionally common in Asia. Paine, Steinbauer, and Lawson (2011) thought the risk was greatest from insects on native eucalypts in near-neighbors Papua New Guinea, Timor, and The Philippines. An earlier risk assessment evaluating 10 insect species from the region concluded that most are polyphagous and probably switched to eucalypts. Two woodborers – Agrilus opulentus and A. sexsignatus –seem to have coevolved with Eucalyptus deglupta in New Guinea and The Philippines.

According to the same authors, most of the insects that have switched hosts are either polyphagous or normally feed on other myrtaceous species native to these regions. Thus, the Brazilian moth Thyrinteina arnobia feeds on Psidium guajava and several other Myrtaceae. Sarsina violascens is also a pest of Psidium species, as well as species in the Asteraceae, and Oleaceae. And the foliar rust Austropuccinia psidii was first described from Psidium guajava in Brazil and boasts a wide host range in the Myrtaceae in South America. It has been introduced to many regions with plants in the Myrtaceae, notably Hawai`i, Australia, South Africa, New Caledonia, and New Zealand. At least 15 Myrtaceae species in Australia are threatened with extinction.

Still, few non-native insects were damaging eucalypts in Australia’s native forests or plantations as of 2011. Those few are highly polyphagous. Several, if not most, were introduced in the first half of the 20^th Century.

Why so few? Paine, Steinbauer, and Lawson (2011) suggest three possibilities: (a) Australia’s diverse endemic insects already occupy most niches, so they exclude new, foreign competitors; (b) most introduced insects were not previously exposed to Myrtaceae in their native range; and (c) Australia has strong quarantine procedures aiming to limit introductions of non-native herbivores.

The fact that none of the introduced insects has adapted to feed significantly on mature eucalypts’ above-ground tissues seems to me to point to protection provided by the adult trees’ phytochemicals and leaf structure. Paine, Steinbauer, and Lawson (2011) discuss some aspects of leaf structure and wax coatings.

As to Australia’s quarantine procedures, as I reported before, the country has been much less proactive regarding plant pests and diseases that threaten tree species rather than agricultural crops. Significant new programs were established only after 2000, when Plant Health Australia (PHA) was incorporated. The PHA is supposed to facilitate preparedness and response arrangements between governments and industry for plant pests (once an alien pest has become established, management becomes responsibility of the land manager). In 2005, federal, state, and territorial governments and plant industry bodies signed a legally-binding agreement — the Emergency Plant Pest Response Deed (EPPRD). As of 2022, 38 were engaged. It sets up a process to implement management and funding of agreed responses to the detection of exotic plant pests – including cost-sharing and owner reimbursement.

Still, studies documented significant gaps in post-border forest biosecurity systems and the country’s response to the anticipated introduction of the foliar rust Austropuccinia psidii was disappointing. This prompted yet another initiative: development of the National Forest Biosecurity Surveillance Strategy (NFBSS) in 2018. The strategy was; accompanied by an Implementation Plan and appointment of a National Forest Biosecurity Coordinator. The forest sector fund a significant proportion of the proposed activities for the first five years. Still, Drs. Carnegie and Nahrung thought that in-country forest pest surveillance was still too fragmented.

Paine, Steinbauer, and Lawson (2011) consider the Asian spongy moths Lymantria dispar and Orgyia thyellina to pose serious threats. Five eucalypt species were assessed to be at risk of attack as are two preferred host oaks in Europe, Quercus pubescens and Q. robur. They note high volumes of imports from East Asia of containers, vehicles, and machinery, which are known to transport spongy moth egg-masses. It is not known whether the numerous natural enemies of Australia’s diverse lymantriid fauna [which includes four in the genus Lymantria] might provide some protection. These experts also worried that the highly polyphagous Asian longhorned beetle (Anoplophora glabripennis) might arrive in Australia. Eucalypts are not recognized as hosts.

Australia has adopted an enhanced surveillance program for ships arriving from Asian and European Lymantria ranges during female flight periods. Described here. Nahrung and Carnegie (2021) though that the high priority assigned to Lepidoptera exceeded the actual risk; only two non-native species had established in Australia over 130 years.

Paine, Steinbauer, and Lawson (2011) suggest several research topics aimed at reducing the risk to eucalypts in Australia. These include interactions between these insects and mechanisms by which insects adapt to new hosts; host chemistry and resistance mechanisms), chemical ecology (including host selection), population and community dynamics, including possible biocontrol agents, and pathway and risk analysis.

On the other hand, Carnegie and Nahrung (2019) called for developing more effective methods of detection, especially of Hemiptera and pathogens. They also promoted national standardization of data collection. Finally, they advocated inclusion of technical experts from state governments, research organizations and industry in developing and implementing responses to pest incursions. They noted that surveillance and management programs must expect and be prepared to respond to introductions of unanticipated species. They had found that 85% of the pests detected over the last 20 years—and 75% of subsequently mid-to high-impact species established—were not on high-priority pest list.

SOURCES

Carnegie A.J. and H.F. Nahrung. 2019. Post-Border Forest Biosecurity in AU: Response to Recent Exotic Detections, Current Surveillance and Ongoing Needs. Forests 2019, 10, 336; doi:10.3390/f10040336 www.mdpi.com/journal/forests

Nahrung, H.F. and A.J. Carnegie. 2021. Border interceptions of forest insects established in Australia: intercepted invaders travel early and often. NeoBiota 64: 69–86. https://doi.org/10.3897/neobiota.64.60424

Paine, T.D., M.J. Steinbauer, and S.A. Lawson. 2011. Native & Exotic Pests of Eucalyptus: A Worldwide Perspective. Annu. Rev. Entomol. 2011. 56:181-201

Native & Exotic Pests of Eucalyptus: A Worldwide Perspective

Posted by Faith Campbell

https://fadingforests.org

Call for new approach to biological conservation – integrating bioinvasion

whitebark pine in Glacier National Park killed by white pine blister rust

The Kunming-Montreal Global Biodiversity Framework (KMGBF) is a major global policy driver around the world for more effective action to preserve biodiversity from current and future threats. (However, the United States has not joined the underlying treaty, the Convention on Biological Diversity (CBD). So its importance is probably less in the United States than in countries that take part.) This relatively new Framework was adopted at the 15^th Conference of the Parties (COP) of the CBD in December 2022 after four years of negotiations. However, cynics note that the 196 countries that are parties to the CBD have rarely met previous ambitious goals set at earlier COP.

Hulme et al. have just published a paper [full reference at the end of this blog] addressing how invasive species and this Framework’s target may interact. They note that conserving biodiversity costs money. Many of the countries hosting diverse and relatively intact ecosystems lack sufficient resources, capability, or robust governance structures for this conservation.

The Kunming-Montreal Global Biodiversity Framework sets out ambitious global targets to reduce biodiversity loss by 2030 so as to maintain the integrity of ecosystems and their constituent species. Of the 23 targets, one – Target 6 – addresses bioinvasion. Countries endorsing the CBD have committed to eliminating, minimizing, reducing and/or mitigating invasive species’ impacts on biodiversity and ecosystem services. This is to be accomplished by identifying and managing introduction pathways; preventing introduction and establishment of priority invasive species; reducing rates of introduction and establishment of known or potential invasive species by at least 50% by 2030; and eradicating or controlling invasive species, especially in priority sites.

I rejoice that the CBD parties have recognized invasive species as a major driver of biodiversity loss in terrestrial and marine ecosystems. I wish conservation organizations’ and funders’ activities clearly reflect this finding.

This is the challenge raised by Hulme et al.: countries must integrate efforts to counter bioinvasions into overall conservation programs. Success in curbing bioinvasion depends upon achieving almost all other KMGBF targets. And this is a two-way street: the more holistic approach offers greater likelihood of successful biodiversity conservation.

The same authors point out that some of the 22 other targets address rapidly evolving introductory pathways e.g.,

Target 15 – increasing international and domestic tourism;
Target 12 – encroachment of urban areas near protected areas;
Target 10 – development of intensive agriculture or aquaculture systems near protected areas;
Target 7 – species rafting on plastic marine pollutants; and
Target 8 – growing risk from species shifting ranges in response to climate change.

pallet graveyard behind camp store & snack bar art Lake MacDonald, Glacier National Park; photo by F.T. Campbell

Other targets relate to management of established invasive species, e.g.,

Target 1 – planning and priority-setting for allocation of limited resources among the various threats to biodiversity;
Identifying factors that pose risks to highly-valued species, e.g., threatened species (Target 4) and species that provide important ecosystem services (Target 11);
Target 19—obtaining necessary financial resources.

A final group of targets are intended to guide all conservation efforts. These goals include integrating biodiversity concerns in decision-making at every level (Target 14); reducing harmful economic incentives and promoting positive incentives (Target 18); and several targets addressing issues of equity, benefit sharing, and access to information. Hulme et al. assert that the threat posed by bioinvasions must be incorporated into policies, regulations, planning and development processes and environmental impact assessments across all levels of government.

Hulme et al. decry an imbalance as to which KMGBF targets have been the focus of attention from governments, conservation organizations, and media. These stakeholders have concentrated on

Target 3, which calls for extending legal protection to 30% of lands and waters by 2030;
Target 4, which promotes maintaining genetic diversity within and among populations of all species;
Target 7, which encourages reducing harmful pollution;
Target 15, which urges businesses to decrease biodiversity risks arising from their operations; and
Target 21, which advocates ensuring equitable and effective biodiversity decision-making.

Even when stakeholders have looked at Target 6, they have focused primarily on how to quantify the numbers of species being introduced to novel ecosystems. Hulme et al. argue that conservationists should instead concentrate on the challenge of achieving the target. They note that bioinvasion is worsening despite implementation of many long-term management programs. As they note, numbers of introduced species globally have increased, these species are occupying larger geographic areas, and the species’ measured impacts have risen to astounding levels (see my previous blog about new cost estimates). This same point was made two years ago by Fenn-Moltu et al. (2023) [full citation at the end of this blog]; they found that the number of invasive species-related legislation and treaties to which a country adheres did not relate to either the number of insect species detected at that country’s border or the number of insect species that had established in that country’s ecosystems.

As conservationists, Hulme et al. remind us that not all damages are monetary: invasive species threaten more than half of all UNESCO World Heritage Sites.

Hulme et al. say achieving Target 6 presents several scientific challenges – most of which have been discussed by numerous other authors. Introduction pathways are changing rapidly. There is great uncertainty regarding current and especially future propagule pressures associated with various pathways. Information about particular species’ impacts and where they are most likely to be introduced is insufficient. Management costs are routinely underestimated. Perhaps most challenging is the need to judge programs’ effectiveness based not simply on outputs (e.g., number of acres cleared of weeds) but on outcomes in relation to reducing the subsequent impact on biodiversity and ecosystem services.

I note that several environmental organizations endorsed a “platform” that discussed this last point a decade ago. [I have rescued the NECIS document from a non-secure website; if you wish to obtain a copy, contact me directly through the “comment” option or my email.] Unfortunately, the coalition that prepared this document no longer exists. Even when conservation organizations have invasive species efforts, they are no longer attempting to coordinate their work.

I greatly regret that Hulme et al. continue a long-standing misrepresentation of international border biosecurity controls as consisting primarily of inspections — of imported commodities, travellers, and associated transport conveyances. I have argued for decades that inspections are not effective in preventing introductions. See Fading Forests II Chapter 3 (published in 2003); Fading Forests III Chapter 5 (published in 2014); “briefs” describing pathways of introduction prepared for the Continental Dialogue on Non-Native Forest Insects and Diseases – in 2014 and in 2018.

The weaknesses of visual inspection are especially glaring when trying to prevent introductions via wood packaging material and living plants — also here.

Hulme et al. propose a politically astute approach to finding the resources to strengthen countries’ efforts to curtail invasive species’ spread within their borders. Recognizing that no country has unlimited resources to allocate to managing invasive species, they suggest concentrating slow-the-spread efforts on preventing damage to legally protected areas. Furthermore, authorities should avoid designating as new “protected areas” places that are already heavily invaded – or at risk of soon becoming so. As they note, programs aimed at protecting these areas often engage conservation stakeholders, decision-makers, even potential non-governmental donors. In other words, there is a foundation on which to build.

To buttress their argument, Hulme et al. cite evidence that bioinvasions threaten these areas’ integrity. For example, Cadotte et al. (2024) found that bioinvasion is one of most frequently identified threats identified in a survey of 230 World Heritage sites; and that they pose a greater degree of concern than other threats to biodiversity. They reiterate that managing invasive species is one of the most effective interventions aimed at protecting biodiversity.

The task remains complex. Hulme et al. note that accurate information about pressure caused by invasive species is not easily quantified using remote sensing. It requires expensive on-the-ground data collection. Even current methods for ranking invasive species have crucial gaps regarding species’ potential impact and the feasibility of their control. Choosing management strategies also requires assessing potential unintended effects on biodiversity and other GBF Targets, e.g., pollution from pesticides (Target 7).

Still, the context remains: successful management of bioinvasions to support the integrity of protected areas depends on the integrative approach described above.

Hulme et al. note a contradiction within the Kunming-Montreal Global Biodiversity Framework: Target 10 calls for the agriculture, aquaculture, and forestry industries to adopt sustainable practices, but doesn’t raise the issue of these sectors’ role in the introduction and spread of invasive species. They say guidelines have been developed for sustainable forestry production. These guidelines recommend that commercial plantation forests not plant non-native tree species within 10 km of a protected area. Hulme et al. also suggest applying a “polluter pays” fine or bond to forestry businesses that use invasive species without sufficient safeguards to prevent escape. These funds could be accessed to support invasive species management in protected areas, particularly surveillance. (Target 19 mandates obtaining more funds for this purpose). They add that these aquaculture, agriculture, horticulture and forestry sectors should take action to prevent the local feralization of alien crops and livestock.

Target 8 calls for minimizing the impacts of climate change on biodiversity. Hulme et al. note numerous scientific challenges here, including understanding how specific ecosystems’ and native species’ are vulnerable to altered climates, along with how specific invasive species’ are responding to an altered climate regime.

These same authors provide specific recommendations to the global conservation community to put in place a more holistic perspective. Some recommendations deal with data integration. Others call for major undertakings: i.e., developing a protected area management toolkit at a global scale. This action will require significant investment in capacity-building of protected area managers plus international cooperation and technology transfer (Target 20). Hulme et al. suggest funding this effort should be a priority for any resources leveraged from international finance (Target 19).

Hulme et al. also propose changes in the conservation approaches advocated by the CBD and IUCN. Specifically, they call for more explicit consideration of current and future impacts of bioinvasions and their management — on protected areas. The needed activities fall into six areas:

(1) reduce risks associated with various pathways;

(2) plan for range-shifting invasive species;

(3) mitigate invasive species’ impacts on biodiversity and (4) on ecosystem services;

(5) ensure new protected areas (including urban green spaces and infrastructure corridors) are largely free of established (“legacy”) invasive species; and

(6) provide managers sufficient resources to take effective action.

SOURCES

Fenn-Moltu, G., S. Ollier, O.K. Bates, A.M. Liebhold, H.F. Nahrung, D.S. Pureswaran, T. Yamanaka, C. Bertelsmeier. 2023. Global flows of insect transport & establishment: The role of biogeography, trade & regulations. Diversity & Distributions DOI: 10.1111/ddi.13772

Hulme, P.E., Lieurance, D., Richardson, D.M., Robinson, T.B. 2025 Multiple targets of Global Biodiversity Framework must be addressed to manage invasive species in protected areas. NeoBiota 99: 149–170. https://doi.org/10.3897/neobiota.99.152680

Posted by Faith Campbell

https://fadingforests.org

Sentinel Gardens – useful tool if microbes scrutinized sufficiently

Northern red oak – one of the species planted in Europe & China as part of sentinel garden project; photo by F.T. Campbell

During the USDA Interagency Forum on Invasive Species, Dr. Eliana Torres Bedoya, from the Bonello lab at Ohio State, provided insights gained from a sentinel garden project operating for the last five years.

The gardens were established in six locations: two in China in the Nanjing area, one each in Italy, Sweden, Ohio, and New Hampshire. The network required collaboration among scientists in several countries, a difficult task in itself. (Jiri Hulcr of the University of Florida has also stressed the importance of mutually beneficial collaborations.)

The focus was on detecting and identifying novel fungal pathogens abroad before they ever enter a country, in an approach called ex patria sentinel plantings. Altogether, 32 tree species were planted in at least one location. For example, Chinese and European tree species were planted in the U.S. to identify potential threats to China and Europe. Conversely, North American species were planted in Europe and China to detect potential threats to the U.S. As noted, the reciprocity is crucial to establishing and maintaining a long-term relationship.

Key information gained to date:

While the scientists isolated several potential pathogens from symptomatic plants, analysis of all plants’ leaf microbiomes showed that asymptomatic plants harbored many more potential pathogens that had not been isolated.

Healthy plants tend to harbor larger and often more diverse microbial communities. This study found that asymptomatic plants supported a significantly more abundant, richer, and taxonomically diverse leaf-associated fungal community than symptomatic plants. Importantly, this pattern pertains also to the subset of taxa classified as potential plant pathogens.

Detection of the full range of fungal pathogens requires that samples must be collected both early and mid-to-late in the growing season because microbes present differ.
Core leaf microbiomes were associated with specific tree species, no matter where they were planted. However, the constituents of the core microbiome were outnumbered by other organisms driven primarily by the location of the planting. This had been expected.

Other contributing factors – in declining order – were geographic location, tree species, season, and host health status. In other words, the phylogenetic relationship.

The drivers of fungal community composition interact in complex ways. For instance, the effect of the plant’s health on pathogenic fungal communities might depend on the host species. This relationship can be further modulated by seasonal variation and geographic context.

European & Asian trees planted in Ohio as part of the sentinel garden program; photo by P (E) Bonello

Implications:

Sentinel gardens can facilitate identification of novel host-pathogen interactions in symptomatic and asymptomatic plants, so they should be adopted / supported by governmental and regional phytosanitary agencies.
The findings demonstrate the need to expand surveillance beyond symptomatic plants – at both sentinel gardens and plant health border inspection stations. Phytosanitary agencies should employ both full microbial community molecular characterization to detect threats in asymptomatic plants and traditional symptom-based approaches. These modern approaches are described in Munck and Bonello 2018 (full reference at end of the blog).
Enrico Bonello (pers. comm.) thinks it is likely that similar context-dependent interactions among host and fungus species, season, and geography also drive disease infection and virulence.

Eliana Torres Bedoya (pers. comm.) clarifies that the leaf microbiome is the community of microorganisms living on and within tree leaves. These microbes can contribute to protecting trees against pathogens, enhance tolerance to environmental stressors such as drought or pollution, and influence how trees interact with their surroundings. Because the composition of the leaf microbiome responds to changes in climate, location, and tree species, it also serves as a valuable indicator of forest health and environmental change.

There are several approaches to studying microbial communities in leaves. One is the traditional, culture-based method, which relies on isolating and cultivating microorganisms on nutrient media. While this approach is effective for recovering fast-growing and easily culturable taxa, it has a major limitation: the vast majority of environmental microbes are not readily culturable under standard laboratory conditions. As a result, full understanding requires use of culture-independent methods. One technique widely used is metabarcoding. This technique involves extracting total DNA from leaf tissue and amplifying a phylogenetically informative genetic marker specific to the microbial group of interest (for example, the internal transcribed spacer (ITS) region for fungi or the 16S rRNA gene for bacteria). The amplified regions are then sequenced using high-throughput sequencing platforms. After a series of processing steps, the sequences are clustered into Amplicon Sequence Variants (ASVs), which represent unique DNA sequences that can be used as proxies for microbial taxa present in the sample. Torres Bedoya and Bonello used the ASVs for comparative analysis.

*Tilia cordata* (linden) via Picaryl (seed wings make a great tea!)

In her presentation, Torres Bedoya provided examples of the complexities arising when trying to detect fungi associated with trees. Eleven potentially pathogenic fungal genera were found to be more abundant in asymptomatic Northern red oak (Quercus rubra) trees (a North American species) planted in both Europe and China. Five ASVs were more abundant in asymptomatic Fraxinus mandshurica trees (an Asian species) planted in Sweden. In this case, the season when the leaves were sampled explained a higher proportion of the variance in the community composition than did the health status of the host. Molecular methods detected 10 genera not revealed through isolation from little-leaf linden species (Tilia cordata) trees (a European species) planted in China and the US.

This “proof of concept” study considered only fungi associated with leaves. As shown above, learning the true plant health risk associated with any tree taxon’s leaves is already complicated and resource-demanding. To fully exploit the power of the ex patria sentinel plantings approach, phytosanitary officials must provide additional resources (land, people, equipment, money) to enable screening of all plant parts, above and below-ground, and all potentially pathogenic taxa, including nematodes, phytoplasmas, and viruses. These systems must be maintained over years.

Reference

Munck, I.A., Bonello, P. 2018. Modern approaches for early detection of forest pathogens are sorely needed in the United States. Forest Pathology 48 (5). doi:10.1111/efp.1445

Posted by Faith Campbell

www.fadingforests.org

Non-Native Moths in England: Ever Upward

*Platyperigea kadenii* — one of the moth species that feeds on native plant species introduced recently to Great Britain. Photo by Tony Morris via Flickr

Will phytosanitary agencies and the international system respond to continuing introductions of non-native species?

A new study confirms that introductions of insects continue apace, links this pattern to the horticultural trade, and examines the role of climate change in facilitating introductions. This study focuses on moths introduced to the United Kingdom (Hordley et al.; full citation at the end of the blog). The study sought to detect any trends in numbers of species establishing and the relative importance of natural dispersal vs. those assisted – intentionally or inadvertently – by human activities.

The authors determined that moths continue to be introduced by both processes; there is no sign of “saturation”. This finding agrees with that of Seebens and 44 others (2017; citation below), which analyzed establishments of all types of non-native species globally. The British scientists found that rapidly increasing global trade is the probable driver of the recent acceleration of human-assisted introductions. They emphasize the horticultural trade’s role specifically. Climate change might play a role in facilitating establishment of species entering the UK via human activities.

Hordley et al. found that long-term changes in climate, not recent rapid anthropogenic warming, was important in facilitating introductions of even those moth species that arrived without human assistance. As they note, temperatures in Great Britain have been rising since the 17^th Century. These changes in temperature have probably made the British climate more suitable for a large number of Lepidoptera. The data show that the rate of natural establishments began rising in the 1930s, 60 years before anthropogenic changes in temperatures became evident. Hordley et al. point out that an earlier study that posited a more significant role for climate change did not distinguish between insect species which have colonized naturally and those benefitting from human assistance.

The authors expect introductions to continue, spurred by ongoing environmental and economic changes. Fortunately, very few of the introduced moths had any direct or indirect negative impacts. (The box-tree moth (Cydalima perspectalis) is the exception. [Box-tree moth is also killing plants in North America.]

boxtree moth; photo by Tony Morris via Flickr

Still, they consider that introductions pose an ongoing potential risk to native biodiversity and related human interests. Therefore, they advocate enhanced biosecurity. Specifically, they urge improved monitoring of natural colonizations and regulation of the horticultural trade.

Hordley et al. estimated the rate of establishment during the period 1900 – 2019 for (i) all moth species; (ii) immigrants (i.e., those introduced without any human assistance); (iii) immigrants which feed on native hosts; (iv) immigrants which feed on non-native hosts; (v) adventives (i.e., species introduced with human assistance); (vi) adventives which feed on native hosts; and (vii) adventives which feed on NIS hosts.

Their analysis used data on 116 moth species that have become established in Great Britain since 1900. Nearly two-thirds of these species – 63% – feed on plant species native to Great Britain; 34% on plant species that have been imported – intentionally or not. Data were lacking on the hosts of 3 species.

Considering the mode of introduction, the authors found that 67% arrived through natural colonization; 33% via human assistance. Sixty-nine percent of the 78 species that were introduced through natural processes (54 species) feed on plant species native to Great Britain; 31% (24 species) feed on non-native plants. Among the 38 species whose introduction was assisted by human activities, one-half (19 species) feed on native plant species; 42% (16 species) feed on introduced hosts.

Regarding trends, they found that when considering all moth species over the full period, 21.5% more species established in each decade than in the previous decade. This average somewhat obscured the startling acceleration of introductions over time: one species was reported as established in the first decade (1900–1909) compared to 18 species in the final decade (2010–2019).

The rate of introduction for all immigrant (naturally introduced) species was 22% increase per decade. Considering immigrant species that feed on native plants, the rate of establishment was nearly the same – 23% increase per decade – when averaged over the 120-year period. However, a more detailed analysis demonstrated that these introductions proceeded at a steady rate until 1935, then accelerated by 11% per decade thereafter. In contrast, immigrants that feed on non-native plants have maintained a steady rate of increasing establishments – 13% per decade since 1900.

Adventive species (those introduced via human assistance) increased by 26% per decade. The data showed no signs of saturation. The rates of introduction were similar for adventives that feed on both native plants (22%) and non-native hosts (26%). Again, additional analysis demonstrated a break in rates for adventives that feed on native hosts. The rate was steady until the 1970s, then significantly increased during the years up to 2010. (The scientists dropped data from the final decade since lags in detection might artificially suppress that number.)

In summary, Hordley et al. found no significant differences in trends between

the number of species that established naturally (20%) vs. adventives (26%).
immigrant or adventive species that feed on native vs. non-native hosts.

The authors discuss the role of climate change facilitating bioinvasion by spurring natural dispersal, changing propagule pressure in source habitats, changing the suitability of receiving habitat, and changing in pathways for natural spread, e.g., altered wind and ocean currents. They recognize that the two modes of colonization – adventives and immigrants – can interact. They stress, however, that the two colonization modes require different interventions.

Although their findings don’t support the premise that a surge of natural colonizers has been prompted by anthropogenic warming, Hordley et al. assert that climate clearly links to increased moth immigration to Britain and increased probability of establishment. They note that even so assisted, colonists still must overcome both the natural barrier of the English Channel and find habitats that are so configured as to facilitate breeding success. They report that source pools do not appear to be depleted — moth species richness of neighboring European countries greatly exceeds that in Great Britain.

I would have liked to learn what factors they think might explain the acceleration in both natural and human-assisted introductions of species that feed on plant species native to Great Britain. In 2023 I noted that scientists have found that numbers of established non-native insect species are driven primarily by diversity of plants – both native and non-indigenous.

Hordley et al. assert that Great Britain has advantages as a study location because as a large island separated from continental Europe by the sea – a natural barrier – colonization events are relatively easy to detect. However the English Channel is only 32 km across at its narrowest point. I wonder, whether this relatively narrow natural barrier might lead to a misleadingly large proportion of introduced species being natural immigrants. I do agree with the authors that moths are an appropriate focal taxon because they are sensitive to climate and can be introduced by international trade. Furthermore, Britain has a long tradition of citizen scientists recording moth sightings, so trends can be assessed over a long period.

Hordley et al. stress that they measured only the temporal rate of new species’ establishments, not colonization pressure or establishment success rate. They had no access to systematic data regarding species that arrived but failed to establish. Therefore, they could not deduce whether the observed increase in establishment rates are due to:

(1) more species arriving—due either to climate-driven changes in dispersal or to accessibility of source pools; or

(2) higher establishment success due to improved habitat and resource availability; or

(3) both.

Hordley et al. noted two limitations to their study. First, they concede that there is unavoidably some subjectivity in classifying each species as colonizing naturally or with human assistance. They tried to minimize this factor by consulting two experts independently and including in the analysis only those species on which there was consensus.

Second, increases in detection effort and effectiveness might explain the recent increases in establishment rates. They agree that more people have become “citizen scientists” since 1970. Also, sampling techniques and resources for species identification have improved considerably. They note, however, that Seebens et al. (2018) tested these factors in their global assessment and found little effect on trends.

Hordley et al. believe that they have addressed a third possible limitation – the lag between introduction and detection – by running their analyses both with and without data from final decade (2010-2019). The results were very similar qualitatively.

SOURCE

Hordley, L.A., E.B. Dennis, R. Fox, M.S. Parsons, T.M. Davis, N.A.D. Bourn. 2024. Increasing rate of moth species establishment over 120 years shows no deceleration. Insect Conserv. Divers. 2024;1–10. DOI: 10.1111/icad.12783

Seebens, H. et al. 2017. No saturation in the accumulation of alien species worldwide. Nature Communications. January 2017. DOI: 10.1038/ncomms14435

Seebens, H. et al. 2018. Global rise in emerging IAS results from increased accessibility of new source pools. Proceedings of the National Academy of Sciences. www.pnas.org/cgi/doi/10.1073/pnas.1719429115

Posted by Faith Campbell

www.fadingforests.org

A newly detected pathogen on elms

I learned at the beginning of August that Canadian scientists have discovered a new pathogen causing wilt disease on American elms (Ulmus americana). The pathogen is Plenodomus tracheiphilus, which is known primarily for causing serious disease in citrus.

P. tracheiphilus is described as common on Alberta’s elm trees, especially in the Edmonton area. It was found on 116 of 200 trees which were sampled – see map. The wilting had previously been blamed on Dothiorella ulmi. I have been unable to find a source for the geographic origin of Dothiorella ulmi; perhaps it is native to North America. It is reported to be present at least from Alberta to Texas. (Presumably if Plenodomus tracheiphilus were in Texas it would have caused obvious symptoms on that state’s citrus crops.)

poster prepared by Alberta Plant Health Lab, Alberta Agriculture & Irrigation, and Society to Prevent Dutch Elm Disease

I am unaware of any North American forest pathologists studying whether this pathogen is also established in the United States, or its possible effects. The discovery in Alberta is the first time this organisms has been associated with disease on elms; I have asked European and North American forest pathologists whether they are looking into possible disease on any of the European or North American elm species. So far, no one reports that s/he has been.

In the meantime, the California Department of Food and Agriculture has begun the process of assigning Plenodomus tracheiphilus the highest pest risk designation for the state. CDFA is worried primarily about damage to the state’s $2.2 billion citrus industry. CDFA is seeking comments on its proposed action; go here .

CDFA points out that despite awareness of the disease on economically important citrus since at least 1900 and efforts by phytosanitary agencies, it has spread to most citrus-growing countries around the Mediterranean and Black seas and parts of the Middle East. The primary mode of spread is movement of infected plant material, e.g., rootstocks, grafted plants, scions, budwood, and even fruit peduncles and leaves. Transmission is possible from latently infected, asymptomatic material. Once established at a site, the conidia produced on diseased plant parts can be spread over relatively short distances by rain-splash, overhead irrigation, water surface flow, or wind-driven rain. Transport by birds and insects is also suspected. The pathogen can survive on pruned material or in soil containing infected plant debris for up to four month.

The report from Canada does not speculate on how a disease associated with plants in a Mediterranean climate was transported to Alberta, which has a cold continental climate. Nor is there any information on the possible presence of the disease on elms in warmer parts of Canada.

U.S. elms appear to be at high risk because phytosanitary restrictions leave dangerous gaps.

First, under the Not Authorized for Importation Pending Pest Risk assessment (NAPPRA) program, USDA APHIS has prohibited importation of plants in the Ulmus genus from all countries except Canada. Second, importation of cut greenery is allowed from all countries – and the CDFA analysis indicates that the pathogen can be transported on leaves. Third, it appears to me that it is probable that this pathogen survives on plants in additional taxa.

See this profile for a description of other threats to North American elms.

SOURCES

Poster prepared by Alberta Plant Health Lab, Alberta Agriculture & Irrigation, and Society to Prevent Dutch Elm Disease https://www.alberta.ca/system/files/agi-plenodomus-poster.pdf

Yang, Y., H. Fu, K. Zahr, S. Xue, J. Calpas, K. Demilliano, et al. 2024. Plenodomus tracheiphilus, but not Dothiorella ulmi, causes wilt disease on elm trees in Alberta, Canada. European Journal of Plant Pathology 169(2):409-420. Last accessed August 1, 2024, from https://link.springer.com/article/10.1007/s10658-024-02836-x

Posted by Faith Campbell

www.fadingforests.org

What I learned at the NPB meeting

The National Plant Board’s members are the lead plant health officials of the states and territories. Many federal officials also attend – from APHIS and DHS Bureau of Customs and Border Protection. Representatives of other North American phytosanitary entities participate – i.e., Canada, Mexico, and the North American Plant Protection Organization (NAPPO). Some stakeholder groups participate, especially the nursery industry. I have attended these meetings for over a decade because they provide an overview of pest issues and programs plus an unparalleled opportunity to network. The Nature Conservancy’s Leigh Greenwood also attends. We are the only representatives of the species conservation community to attend – others are missing great opportunities.

Here, I’ve listed 10 items that are among the most important the group discussed.

1) The funding situation for APHIS is worse than I realized

APHIS Administrator Mike Watson and Deputy Administrator (for plants) Mark Davidson both spoke about the need to cut programs to stay within the limits set by congressional appropriations. Funding for APHIS, as a whole, was cut only 1% for the current year (Fiscal Year 2024), cost-of-living salary increases mean less money for programs. (I believe Dr. Watson said $41 million less for FY24). If FY25 funding is the same, Congressionally mandated additional payraises will mean an another $20 million decrease in program funding.

Dr. Davidson said that the plant programs (Plant Protection and Quarantine) had been cut by 5% in FY24. However, Congress did not finalize the funding levels until about half-way through the fiscal year – so staying within the limits required even more severe cuts to programs in the remainder of FY24. To stay within these limits, APHIS cut several programs, among them a $3.6 million cut from the “tree and wood pest” program. This meant loss of funds to manage the polyphagous and Kuroshio shot hole borers, smaller cuts for programs managing Asian longhorned beetle and emerald ash borer, and perhaps the Asian flighted spongy moth. They anticipate additional cuts in these programs in FY25. The one bright light is the Section 7721 Plant Pest & Disease Management & Disaster Prevention Program. It provides steady funding for a range of plant health programs. The House version of the still-pending Farm Bill calls for increasing funding for this program by $15 million each year.

Nearly 100% ash trees in Oregon wetland — exposed to spreading EAB. Photo by Wyatt Williams, Oregon Department of Forestry

Remember this when I ask you to lobby for appropriations! If we don’t advocate for funding the programs dealing with “our” pests, they will shrink.

Watkins and Davidson also worry that whoever is the next secretary of USDA might not support the agency when it seeks to withdraw funds to cover emergencies from the Commodity Credit Corporation – as Secretary Vilsack has.

APHIS and the DHS Customs and Border Protection (CBP) both praised a recent regulatory action that increases user fees for importers having goods cleared at ports. Kevin Harriger, CPB official in charge of agriculture programs, said the new funds would allow CBP to hire 700 new agricultural inspectors (currently there are 2,800 agricultural officials). That sounds great, but … when trade and passenger volumes crashed early in the COVID pandemic, things looked dicey for a while. Plus – as I have argued repeatedly – real protection against pest introductions will come from stronger policies, not ramped-up inspections.

Pathologist Bruce Moltzan reported on the USFS Forest Health Protection program. He pointed out that the USFS has a very limited toolbox. In this fiscal year, the program has about $48 million, after salaries, to support its activities. Projects targetting insects receive 70% of the funding; those targetting pathogens 15%.

2) Invasive hornets

Washington State has not found any new nests of the Northern (formerly Asian) giant hornet (Vespa mandarinia). Miraculous!

However, Georgia detected another species, the yellow-legged hornet (Vespa velutina), near Savannah in August 2023. The Georgia Department of Agriculture, APHIS, and the University of Georgia are working to find nests – which are located at the top of tall pine trees in residential areas. Five nests were found in 2023; another four so far in 2024. Georgia hopes to place traps 100 miles out from each detection site. Like the northern hornet, V. velutina preys on honey bees. It was probably transported by ship or with its cargo.

A third species, V. tropica, has been introduced on Guam.

3) Better Federal-State Cooperation — Sometimes

APHIS and the state phytosanitary officials have set up structures – e.g., Strategic Alliance/Strategic Initiative, or SASI – to work together more closely. CBP joins the coordinating meetings. One program described at the meeting is the effort to contain spread of the box tree moth (Cydalima perspectalis). This effort came out of discussions at last year’s Plant Board meeting, with follow-up gatherings of APHIS, the states, and the nursery industry. The moth is known to be present in New York, Massachusetts, Michigan, Ohio, and now Delaware – plus several Canadian provinces.

A second project concerns how much data to share about state detections of pests – which are recorded in the National Plant diagnostic Network database. These data have accrued over 20 years … and are sought by both other states and academic researchers. States are often reluctant to allow public review of detection data because they fear it will cause other states or private parties to avoid buying plants or other goods from the infested area. While the project team has not yet decided how to deal with these conflicts, they said they were more inclined to share “nonconsequential data” – meaning data on a pest everyone already knows is present, not a pest under regulation or a new detection. In other words, “consequential” seems to pertain to industry profits, not damage to agricultural or natural resources.

EAB-killed ash along Mattawoman Creek, Maryland. Photo by Leslie A. Brice

4) Update: 20 years of tackling the emerald ash borer

Craig Kellogg, APHIS’ chief plant health representative in Michigan, reviewed 20 years of dealing with the emerald ash borer (EAB). He is optimistic about the impact of the biocontrol agents that have now been released in 32 states and four provinces. The larval parasitoids are dispersing and EAB densities are coming down. He conceded that over-story and mature ash are still dying, but says ash in long-infested areas are regenerating well. Scientists agree (see Wilson et al. 2024; full citation at end of the blog). Woodpeckers are still the most effective biocontrol agent of EAB for over-story ash, especially in locations where introduced parasitoids are not established. So far, the growing numbers of biocontrol agents are still parasitizing too few EAB larvae to prevent decline of over-story ash trees.

5) Flighted Spongy Moths

APHIS reported on recent detections of flighted spongy moth from Asia on ships coming to U.S. ports. The program covers four closely related species of Lymantria. All have much broader host ranges than Lymantria dispar, plus the females are capable of sustained flight, so they spread more rapidly.

The principal strategy to prevent their introduction is to require ships that call at ports along the Pacific coast in Russia, China, Japan, and North and South Korea to ensure that the ships’ superstructures and cargo are clean. Before arriving at U.S. ports, the ship’s captain must inform CBP where it has called over the last 24 months. Then, CBP conducts an inspection. If CBP inspectors find a small number of egg masses, they remove the eggs and spray pesticide. If the inspectors detect a large number of egg masses, the ship is ordered to leave port, clean itself, and undergo re-inspection before it can return.

Four countries in the Americas – the U.S., Canada, Chile, and Argentina – and also New Zealand have very similar programs.

Detections follow natural changes in population levels in the exporting regions. APHIS’ program leader, Ingrid Asmundsson, reported on an unfortunate coincidence in 2014. A huge moth population outbreak occurred simultaneously with very low fuel prices in Russia. The latter attracted many ships to call there. An even bigger population surge occurred in 2019. Asmundsson expects another high-moth period this year.

flighted spongy moths infesting a ship superstructure

APHIS is working on putting this program on a regulatory foundation; this would allow the agency to be more specific in its requirements and to impose penalties (other than expulsions from ports). I’ll let you know when the proposed rule is published for comment.

6) Regional Reports: Old Pests, New Pests

Representatives of the regional plant boards informed us of their “new pest” or other concerns.

Gary Fish, president of the Eastern Plant Board, mentioned

the need for additional research on management of beech leaf disease
concern about impact of box tree moth and vascular streak dieback on the nursery industry (the latter is a threat to dogwood and redbud)
spread of elm zig-zag sawfly in Vermont and Connecticut
awareness that laurel wilt is moving into Virginia and maybe farther north.

elm zig-zag sawfly; photo by Gyorgy Csoka *via* Bugwood

There was a more general discussion of beech leaf disease. What can be done, given that the disease is so widespread that no one is regulating movement of beech. Gary Fish advised outreach and efforts to reach agreement on management approaches. Chris Benemann, of Oregon, suggested informing other states so that they can decide whether to take regulatory action. A representative of CBP urged engaging stakeholders by asking for their help.

Chris Benemann, President of the Western Plant Board, expressed concern about APHIS’ reduced funding for spongy moth detection and control efforts. She also worries about the recently detected population of Phytophthora austrocedrii in an Oregon nursery. The western states are also focused on several longstanding pest problems – grasshoppers, Japanese beetle; and a new beetle from Australia that is attacking almonds, pistachios, and walnuts.

tree infested by hemlock woolly adelgid; photo by F.T. Campbell

Megan Abraham of Indiana reported that members of the Central Plant Board are concerned about

funding decrease for APHIS and USFS efforts to slow the spread of spongy moth and manage Asian longhorned beetle and emerald ash borer;
Invaders associated with Christmas decorations, e.g., hemlock woolly adelgid, elongate hemlock scale, and balsam woolly adelgid
spotted lanternfly finding new ways to travel;
invasion by beech leaf disease and possibly by sudden oak death;
elm zig-zag sawfly entering the region;
boxwood blight, potato pests, honeybee pests, and invasive plants – e.g., Hydrilla.

She noted that nursery stock is increasingly coming from more distant – and cheaper – producers, raising the risk of new pests being introduced.

Finally, Abraham expressed concern about decreased funding at the same time as the need is growing – and asked with whom states should collaborate in order to reverse this trend.

Kenny Naylor of Oklahoma, Vice President of the Southern Plant Board, concurred that funding levels are a major concern. He mentioned specifically the spongy moth Slow the Spread program and eradication of the Asian longhorned beetle outbreak in South Carolina. Another concern is the Georgia hornet outbreak.

7) Phasing Out Post-Entry Quarantine

APHIS and the NPB have agreed to phase out the post-entry quarantine (PEQ) program. A program review revealed several problems, some of which astound me. When examining plants in quarantine the scientists still relying on visual inspection! And they are looking for pests identified 45 years ago (1980)! While I think PEQ programs can be valuable in preventing introduction of disease agents, as implemented in recent decades it does not. Twenty years ago, citrus longhorned beetles escaped from a “quarantine” area in a commercial nursery in Washington state. These Cerambycids are more than an inch long!

citrus longhorned beetle; photo by Art Wagner, USDA *via* Bugwood

Part of this phase-out is to transfer plant species harboring pests of concern to the Not Authorized for Importation Pending Pest Risk Assessment (NAPPRA). While the APHIS speaker said that NAPPRA allows the agency to act quickly when it detects evidence of pest risk, I have found lengthy delays. The third round of proposals was published in December 2019! The fourth round of species proposed for NAPPRA listing should be published soon; a fifth round is now in draft inside the agency.

8) Christmas Greens – Spreading Pests

Officials from Oregon, Maine, and Illinois described their concerns about pests being spread by shipments of various forest or plant products, especially Christmas greens. Mentioned were spongy moths, link hemlock woolly adelgid, link elongate hemlock scale, balsam woolly adelgid, link and box wood moth. Part of the challenge is that the vectoring items are often sold by unregulated outlets – multiple stores, Christmas tree lots – and through on-line or catalog outlets. There are also extreme demands on the regulatory enforcement staff during the brief holiday sales season. Several states are unsure whether they have authority over decorative products – although others pointed out that they are regulating the pest, regardless of the object for sale or type of store.

9) Pests in Firewood

Leigh Greenwood of The Nature Conservancy noted that the state agencies that issue firewood regulations – often the plant protection organization (state department of agriculture) — do a good job alerting the public about the risks and rules. However, the public looks first to state parks agencies for information about camping – and those agencies have less robust educational efforts. It is important to put the message where the public can find it when they don’t know it exists – before they include firewood from home in their camping gear.

10) Projects of the North American Plant Protection Organization

The North American Plant Protection Organization (NAPPO) is working on several projects of interest to those of us concerned about tree-killing pests. One project is evaluating risks associated with wood products, especially how well one international regulation, ISPM#15 is working for dunnage. Another projects is testing the efficacy of the heat treatment specified by ISPM#15 (50^o C for 30 minutes). A third project — almost completed – is evaluating fumigants that can be alternatives to methyl bromide.

In conclusion, each annual meeting of the National Plant Board is packed with new information, updates on current pests, and comments on by the state agencies who suggest new approached to APHIS and hold the agency to account. It is well worth attending. Information about upcoming meetings of both the national and four regional plant boards is posted on the NPB website, https://www.nationalplantboard.org/

Signatories to the APHIS-NPB strategic alliance

SOURCE

Wilson, C.J., T.R. Petrice, T.M. Poland, and D.G. McCullough. 2024. Tree species richness and ash density have variable effects on emerald ash borer biological control by woodpeckers & parasitoid wasps in post-invasion white ash stands. Environmental Entomology.

Posted by Faith Campbell