Category: forest pathogens

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

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

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.

Nunez Chapa

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

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

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 20th 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

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

A New Year …Will there be a new priority on countering invasive species?

Alaska yellow cedar (Chamaecyparis nootkatensis); one of the species vulnerable to Phytophthora austrocedri; APHIS has determined it is too late to try to slow its spread. Photo by Nucatum amygdalarum via Wikimedia

On 30 December 2025, US Department of Agriculture Secretary Brooke L. Rollins issued a Secretary’s Memorandum setting five new priorities for research and development. One is to protect agriculture from invasive species. Another is to resolve longstanding trade barriers due to sanitary and phytosanitary concerns.

The Secretary’s intention is to strengthen US agriculture to benefit both farmers and consumers. He justifies the action by claiming that President Lincoln’s original purpose in establishing USDA was to acquire and diffuse useful information on subjects connected with agriculture. According to this interpretation, Lincoln recognized that working to improve agriculture and secure the nation’s food supply would benefit everyone. The emphasis on research and development was reiterated by the almost simultaneous adoption of the Morrill Act of 1862, which created the system of land-grant universities and development of the Cooperative Extension System via the Smith-Lever Act of 1914.

The memorandum specifies five priority areas of research to be pursued by all USDA agencies and offices – to the maximum extent permitted by law and in accordance with any applicable regulations and procedural requirements.

  1. Increasing Profitability of Farmers & Ranchers — especially reducing volatility in profitability. Goals include reducing inputs or increasing mechanization and automation.
  2. Expanding Markets for US agricultural products. Two approaches are mentioned: generating science and data to resolve longstanding sanitary and phytosanitary trade barriers; and expanding use of agricultural commodities in novel biobased products and bioenergy.
  3. Protecting the Integrity of American agriculture from Invasive Species. The memorandum lists four examples of current invasive pest and pathogen threats: new world screwworm in Mexico; continued westward expansion of spotted lanternfly; persistence of highly pathogenic avian influenza in poultry flocks; and citrus greening. It notes that invasive species threaten both agriculture and natural resources. The research is to focus on new and effective methods for preventing, detecting, controlling,and eradicating these threats.
  4. Promoting Soil Health to Regenerate Long-Term Productivity of Land. The research is to promote soil health practices, increase water-use efficiency, & reduce the need for inputs.
  5. Improving Human Health through Precision Nutrition and Food Quality. Research on “precision nutrition” is said to improve understanding of how healthy dietary patterns impact individuals. Research will also focus on increasing foods’ nutritional content and quality.
Vaccinium myrtillus (photo by Anneli Salo via WikiMedia); one of several species in genera shared with North America that are infected by Phytophthora spp in the Italian alps

The memorandum also instructs USDA’s Office of the Chief Scientist (that is, the Under Secretary for Research, Education, & Economics) to coordinate these priorities within USDA and among key partners in other federal agencies.

Does This Policy Mean Substantially Stronger USDA Efforts to Counter Bioinvasions?

Can we expect new energy in USDA’s programs aimed at managing non-native forest pests and invasive plants that damage forests, wetlands, grasslands, and other natural systems? The first paragraph of the memorandum states that it is USDA policy to reaffirm a focus on the Department’s original objectives of maximizing and promoting American agriculture; ensuring a safe, nutritious, and secure food supply; enhancing rural prosperity; and protecting our National Forests & Grasslands. That is promising.

The explicit recognition that invasive species pose severe threats to both agriculture and natural resources is also promising. I welcome the inclusion of two plant pests among the examples. Livestock diseases usually receive far more attention in USDA pronouncements.

I note three caveats:

  • The prominence of enhancing markets for US agricultural exports (# 2). In the past, this longstanding emphasis has led to undercutting phytosanitary agencies’ ability to counter suspected — but incompletely understood — pest risks. I discussed the impracticality of determining a newly detected species’ probable impacts in Chapter 3 of my report, Fading Forests II.
  • The memorandum makes no reference to implementing stronger sanitary or phytosanitary policies. In my view, the Animal and Plant Health Inspection Service has sufficient knowledge to support adoption of a more assertive regulatory stance with regard to both new introductions and spread within the country? Does the memorandum signal support for such a stance by high-ranking USDA officials?

These officials have often reminded APHIS that it is not a research agency.  However, its staff do “methods development” and it funds considerable research through the Plant Pest and Disease Management and Disaster Prevention Programs – Section 7721 of the Plant Protection Act and a matching program for animal diseases.

  • The US Forest Service does have a research division – although the Trump Administration proposed its virtual elimination in early 2025. The Congressional appropriators have provided funding for USFS R&D – but those bills have not yet been enacted into law. I have complained for years that USFS R&D allocates too few resources (about 1% of the total budget) to research on introduced pests and disease pathogens. Might this new directive help fix this problem?

I hope the emphasis on protecting National Forests & Grasslands does not result in narrowing the types of invasive pests addressed.

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

Welcome high-level attention to bioinvasions – although key issues remain unresolved

Japanese knotweed (Reynoutria japonica) – one of the worst invaders around globe. Photo by Will Parson, Chesapeake Bay Program via Flickr

On 23 October, Science published a five-page, data-packed analysis of bioinvasion impacts on terrestrial ecosystems!!! 

Thakur, Gu, van Kleunen, and Zhou (full citation at end of this blog) analyzed 775 studies with the goal of improving understanding of factors contributing to invasions’ impacts – as distinct from “invasibility” (ability to establish). This knowledge is essential to assessing the risk posed by introduced species and setting priorities for management. They analyzed five ecological contexts—diversity of native species and introduced species in the recipient systems, latitude, invader residence time, and invader traits.

They concluded that ecological factors commonly used to explain invasion success do not consistently translate into strong predictors of invasion impacts. Impacts vary in response to the context of the invasion.

[In January 2026, the authors announced changes in details of the article due to some errors in the database and their understanding of it. (Science 8 Jan 2026 Vol. 391 Issue 6781) They conclude that the corrected analysis did not alter the trends described or the overall conclusions.]

limber pine (Pinus flexilis) – one of the species killed by Cronartium ribicoli; photo by F.T. Campbell

Among the studies available for analysis, reports on plants dominated: 605 focused on plant invasions, 114 on animal invasions, and only 56 on microbial invasions. Among the animals were one study of Adelges tsugae (hemlock woolly adelgid), two studies of Agrilus planipennis (emerald ash borer) and one study each of Lymantria dispar (spongy moth), and Ips pini (North American pine engraver). Studies also addressed earthworms, ants, rats, and feral hogs. Microorganisms included Cronartium ribicoli (white pine blister rust) and several Phytophthora species, including P. agathidicida (kauri dieback), P. alni (affects alders), and P. ramorum (sudden oak death).

Thakur et al. note the skewed taxonomic coverage and say that the low number and narrow taxonomic/ecological variety in the animals and microorganisms probably limit their ability to reach robust conclusions about the impacts of such invasions.

The most consistent negative impact they found is reductions in native plant diversity. While this is not surprising given the studies analyzed, I think it is still important since it counters the widespread sense that plant invasions are somehow less deserving of a robust response.

The authors also detected some broader ecosystem impacts of plant invasions. Plant invasions increased soil organic carbon; soil nitrogen (ammonium and nitrate), and available phosphorus; soil moisture, litter biomass; and emissions of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). The changes in biogeochemical properties might reinforce impacts on native plant communities. The reported increase in greenhouse gas emissions might reflect a bias in the studies so Thakur et al. call for more research to solidify this finding.

High native plant species richness had only a weak overall effect on ecosystem-level impacts. While plant invasions often resulted in higher overall plant species richness, when considering only native community responses, the gain in species numbers did not necessarily indicate conservation benefits. Native plants’ biomass increased after invasion. This might reflect short-term increases in productivity in response to altered resource conditions or structural facilitation, rather than a long-term reversal of competitive exclusion. Finally, the longer the invasive [plant] species had been present, the greater the negative effects on native diversity. However, soil abiotic property impacts weakened over time. In fact, the initial increase in soil organic carbon and total nitrogen disappeared after 6 to 10 years. This development might reflect fertilization of ecosystems by long-established nitrogen-fixing invaders such as non-native legumes.

Traits of non-native plant species related to growth and resource acquisition were overall weak predictors of ecosystem impacts. Thakur et al. consider that this finding reflects the relatively narrow range of specific leaf area exhibited by the plant species studied most commonly.

Consequently, Thakur et al. urge managers to focus on containment and impact mitigation, and to prioritize persistent losses of native plant diversity. When considering abiotic responses that might lessen over time, managers should apply “adaptive monitoring” (which is not defined).

Thakur et al. had greater difficulty determining the impacts of animal and microorganism invasions because of the smaller number of studies. They could not determine the effect of native species richness. The observed decline in soil organic carbon they thought was attributable to the large proportion of studies (9 out of 114) that focused on introduced earthworms. Earthworms reduce organic matter by consuming litter. Mammals were also found to reduce soil organic carbon. Introduced insects had no significant ecosystem effects on soil organic carbon. Non-native animals also increased soil emissions of carbon dioxide and nitrous oxide. The microorganisms included in reviewed studies decreased soil ammonium and increased nitrate, consistent with elevated nitrification. While data on body size of invasive animals were sparse, the authors could determine that larger-bodied species tended to increase soil nitrate while reducing effects on total soil N.

Applying the Results

Thakur et al. report that residence time outperformed other factors as a predictor of invasion impacts. The authors regret the scarcity of long-term studies, especially in the Global South, that could increase our understanding of whether these impacts persist or shift under sustained invasion pressure.

How can scientists apply this information in risk assessments evaluating not-yet introduced species or in deciding what is the appropriate intensity of immediate response to newly detected incursions. Should they give greater weight to others’ studies that focus on long-established invasions by the species in question? Otherwise, this finding seems to largely duplicate the long-established “invasion curve”.

I hope scientists will note that observational studies generally showed stronger impacts than experimental ones, particularly in the case of plant invasions. Perhaps this is true because observational studies better incorporate environmental heterogeneity and longer time spans.

Agrostis stolonifera – one of the plants invading on Prince Edward Island, an Antarctic region island under South African jurisdiction. Photo by Stefan Iefnaer via Wikimedia

Thakur et al. note that one factor they analyzed, “latitude”, incorporates several ecological and anthropogenic components relevant to invasion impacts. One element is the greater native bioidiversity in warmer, lower-latitude, regions. According to the “biotic resistance” hypothesis, greater diversity might make these systems more resistant to bioinvasion. However, the situation is complicated by the fact that temperate regions have also often experienced longstanding and intensive land-use modifications — which are believed to facilitate invasive species establishment and spread. I regret that the authors make no attempt to separate the effects of factors that are anthropogenic from those arising from immutable conditions, e.g., latitude, topography, weather patterns, etc.

Thakur et al. call for more studies that cover a wider geographic range. In addition, the studies should include more experimental designs and explore the relationship between invaders’ traits and impacts — especially regarding animals and microbes.

SOURCE

Thakur, M.P., Z. Gu, M. van Kleunen, X. Zhou. 2025.  Invasion impacts in terrestrial ecosystems: Global patterns and predictors. Science 23 October 2025

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

Threats to Spring

Erythronium americanum dominating herb layer in woods owned by the Institute for Advanced Studies, Princeton, in the 1970s; photo by F.T. Campbell

I fell in love with spring ephemerals in the woods of the Institute for Advanced Studies in Princeton. While the degree I was pursuing had no relationship to birding in the swamp, I spent a lot of time enjoying the woods. At that time, more than 50 years ago, the herbaceous layer was dominated by spring beauties (Claytonia virginica), trout lilies (Erythronium americanum), and violets (Viola species).

Beyond the beauty that delights us (or at least, me!), spring ephemerals are important ecologically. They support specialist pollinators and reduce nutrient losses at a time of year when vegetation cover is low and leaching and runoff rates high.

In the decades since I left Princeton, scientists and nature lovers have observed declines in native understory plant communities. These are predicted to continue due to invasion by plants and worms, worm blogs herbivore pressure by deer, E NPS blog, Blossey blog land use changes, and climate change.

Where I live, in the suburbs of the District of Columbia, these forces are clear. The formerly glorious riparian forests where I walk are overrun by invasive plants. The herb layer is dominated by Japanese stiltgrass (Microstegium vimineum) and – increasingly — lesser celandine (Ficaria verna = Ranunculus ficaria). (I found it interesting that Ficaria began taking over floodplain forests only in the last decades of the 20th century, although it was introduced more than 100 years earlier.) Many invasive shrubs (Rosa multiflora, various Lonicera species. …) and vines (Ampelopsis sp, Orbiculatus, Lonicera japonica, Hedera helix …) compound the problem. While I am not sure whether most earthworms here are native or not, high deer populations certainly are a factor.

Ficaria invasion in Fairfax County, Virginia in 2023; photo by F.T. Campbell

So I rejoice that scientists are studying how one taxon of spring ephemerals, trout lilies – Erythronium species – are coping with individual and combined threats. Gutiérrez and Hovick (full citation at the end of this blog) investigated how two species of Erythronium performed in the absence of a leaf litter layer – with and without competition by Ficaria. They chose to manipulate leaf litter as a proxy for impacts from invasive earthworms and non-native shrubs, especially those with rapidly decomposing leaves.  They refer to others’ studies focused on different spring ephemerals.

Gutiérrez and Hovick found that the absence of leaf litter reduced asexual reproduction (corm biomass) in both Erythronium albidum and E. americanum species by 30%. That is, the absence of leaf litter alone reduced the native plants’ performance. This is alarming because persistent leaf litter has been reduced across much of the deciduous forests of eastern North America as a result of action by invasive earthworms and the rapid decomposition of the leaves of most invasive shrubs.

Trout lilies’ performance declined even more when litter absence was coupled with direct competition from Ficaria. Under those conditions, corm biomass declined by 50%. Impacts by lesser celandine occurred despite these plants’ being smaller than counterparts in nearby woodlands. The reduced size of Erythronium corms was sufficient, in their view, to reduce the likelihood that Erythronium would flower to nearly zero. This has clear implications for the long-term population viability of Erythronium andtheir specialist pollinators.

 Gutiérrez and Hovick conclude restoration of these floodplain forests’ herb layer must incorporate management strategies that not only reduce Ficaria’s presence but also restore leaf litter.

Erythronium albidum along Accotink Creek in Fairfax County, Virginia; photo by F.T. Campbell

Underlying Factors

Native spring ephemerals in eastern North America evolved to emerge through litter layers in early spring. The litter layers impose both costs and benefits. In response to shading by leaf litter, Erythronium produces larger petioles compared to same-sized leaves, thus reducing the proportion of resources allocated to building photosynthetic tissue. In these cases, the corms that both perpetuate the individual and carry out asexual reproduction are smaller.

On the other hand, leaf litter increases moisture retention and reduces frost damage by buffering soil temperatures. While these results were seen in their experiment, Gutiérrez and Hovick believe the benefits are greater in nature than demonstrated in the study using potted plants. Leaf litter also increases nutrient availability, directly by increasing supply and indirectly by facilitating fine root growth. In this context, they note that their experiment used litter composed of just two tree species — red oak (Quercus rubra) and red maple (Acer rubrum). This narrow sample probably failed to capture the varied properties of other tree species’ litter and associated microbial activity.

Erythronium americanum along Pohick Creek; photo by F.T. Campbelle

Plants in the Erythronium genus reproduce primarily asexually through producing runners that form corms. The parent corm and runners disintegrate before summer dormancy; the offspring corms persist. Some individuals do not reproduce asexually; they simply replenish their own corm.

The few previous studies give mixed results regarding lesser celandine’s impacts on co-occurring native herbaceous plants (see the summaries in Gutiérrez and Hovick). The authors do not explicitly say whether lesser celandine is usually associated with low litter levels, but that appears to be the implication. They do say that it is not clear whether lesser celandine drives leaf litter loss by altering soil physiochemistry and microbial activity. Or, rather, that it simply performs well when leaf litter is absent.

Where lesser celandine and Erythronium co-occur at high densities, the former’s biomass per square meter can be more than an order of magnitude higher than Erythronium. Gutiérrez and Hovick suggest that competition between the species is primarily belowground. They cite their finding that by the time Erythronium shoots matured, lesser celandine roots occupied most of the belowground pot volume. They expect belowground competition in forests to be even more pronounced because of accumulated lesser celandine root biomass.

Aboveground, the principal factor appears to be the necessity for trout lilies to grow longer petioles to raise their leaves above lesser celandine rosettes, perhaps starving leaf formation. Since leaves are the plant’s photosynthetic organ, this tradeoff could ultimately result in fewer resources returned to the corm for future growth and reproduction. Although Gutiérrez and Hovick also mention that lesser celandine competition might delay Erythronium emergence and flowering, they do not discuss that.

A factor not mentioned by Gutiérrez and Hovick is the probability that Ficaria verna is allelopathic. See the article by Kendra Cipollini listed as a source at the end if this blog.

one of the few floodplains in Fairfax County still dominated by native herbs – Pohick Creek in the Burke area of Fairfax County, Virginia. Note the prevalence of beech in the canopy and subcanopy! photo by F.T. Campbell

Details of Impaired Performance of Erythronium

At the time of senescence, Erythronium plants grown in pots with leaf litter were nearly twice as large as those grown in bare soil conditions. One-third of their offspring corms grew to be larger than the putative biomass threshold for flowering. Only 9% of corms of plants grown in bare soil and 2% (one individual) of those grown with lesser celandine did. As noted above, corms developed by Erythronium grown in the presence of Ficaria actually lost biomass. This is the basis for their conclusion that there would be almost no sexual reproduction the following year where litter was absent and lesser celandine present.

Gutiérrez and Hovick think the principle mechanisms by which leaf litter affects performance of Erythronium plants is by buffering temperature ranges and increasing moisture retention. Indeed, they found that daily temperature ranges and maxima of soil in pots with bare soil or lesser celandine plants were both higher than temperatures under leaf litter. Reducing temperature maxima could be especially important with the increasing frequency and intensity of late-spring heatwaves associated with climate change. Absence of leaf litter advanced trout lily’s shoot emergence, flower emergence, and petal opening by 14 or more days.

This change might expose the plants to increased risk of frost damage. These dynamics will be system-specific, especially with complications added by climate change. However, Therefore, Gutiérrez and Hovick encourage future research to explore species-specific litter effects on spring ephemerals.

Broader Implications

Their findings regarding these two species of spring ephemerals prompt Gutiérrez and Hovick to assert that negative impacts from invasive plant species might be especially underestimated in spring ephemeral communities due to the combination of their short period of annual aboveground activity and tendency towards long lives. Changes might be very subtle over short timeframes.

They add that it is important to learn the role different conditions might play in the futures of related species. The two species’ ranges largely overlap, but E. americanum extends into the extreme southeast and northeast, E. albidum into the prairie states. Although these species’ respond to loss of leaf litter and lesser celandine invasions in similar ways, the fact that E. albidum occurs in areas of higher soil moisture makes it more vulnerable to negative population-level impacts from lesser celandine invasions.

Note about additional threats

Most of the photos of Erythronium americanum in this blog were taken along a particular creek in Fairfax County, Virginia. Ficaria has just begun to invade this area (see photo above); deer are plentiful. These plants face another bioinvasion: beech leaf disease has arrived. Widespread mortality of the predominantly beech understory will presumably open areas to more light, probably spread of the extant invasive plants.

beech in Fairfax County, Virginia with symptoms of beech leaf disease; photo by F.T. Campbell

SOURCES

Cipollini, K. and K.D. Schradin. 2011. Guilty in the Court of Public Opinion: Testing Presumptive Impacts and Allelopathic Potential of Ranunculus ficaria” 

Gutiérrez, R.G. and S.M. Hovick. 2025. Compounding negative effects of leaf litter absence and belowground competition from an invasive spring ephemeral on native spring ephemeral growth and reproduction. Biol Invasions (2025) 27:213 https://doi.org/10.1007/s10530-025-03668-4

Actions USDA Could Take to Better Protect Our Forests

ohia trees killed by ROD near Pahoa, Hawai`i; with JB Friday; photo by F.T Campbell … APHIS has not applied NAPPRA to this pathogen

As I have documented numerous times in these blogs, [see here, here, here, here, here, here, here and here] forests throughout the world are being reshaped by rising numbers of introduced, non-native pathogens. Once established, these diseases are nearly impossible to contain, much less eradicate.

While the worst effect of such bioinvasions is widespread mortality of host species, even “lesser” results produce significant changes in the impacted ecosystems.

I believe that the international phytosanitary “system” adopted by the World Trade Organization (WTO) and amended by the International Plant Protection Convention (IPPC) in the mid-1990s impedes efforts to prevent introductions of pathogens. These rules require unattainable levels of certainty about an organism’s impacts before it can be restricted. Scientists such as Haoran Wu and Kenneth Raffa have called for phytosanitary approaches that will be more effective because they are realistic, reflect the true level of  threat, and the limits of current science. I agree and have repeated their calls.

How Well Is This “System” Keeping Pathogens At Bay?

  • If the world’s phytosanitary system worked well, we should be seeing fewer high-risk forest pathogens being introduced to new countries. Instead, examples abound of pests invading new ecosystems in the post-WTO/IPPC era: Austropuccinia psdii — detected in Hawai`i in 2005, Japan in 2009, Australia in 2010, China in 2011, New Caledonia and South Africa in 2013, Indonesia and Singapore in 2016, and New Zealand in 2017.
  • Phytophthora ramorum – 8 to 14 additional introductions to California after its initial detection.
  • Fusarium disease vectored by beetles in the Euwallaceae genus:
    • Euwallacea fornicatus s.s.— detected in southern California in 2003, Hawai`i in 2007, Israel in 2009, in South Africa in 2012, in Australia in 2021, and in Argentina and Uruguay in 2023 and 2024 . The haplotype detected in South America and several European greenhouses differs from that established elsewhere.
    • E. kuroshio detected in southern California in 2013; has spread to nearby Mexico  
    • E. interjectus detected in central California in 2024.
  • Boxwood blight fungus Calonectria pseudonaviculata — first detected in the Caucuses in 2010 and the US in 2011. Now established in at least 24 countries in three geographic areas: Europe and western Asia; New Zealand; and North America.  Boxwood blight has caused rapid and intensive defoliation of native stands of Buxus sempervirens. Although disease was detected in United Kingdom in the mid-1990s, the causal agent was not determined until 2002.
  • Beech leaf disease caused by the nematode Litylenchus crenatae subsp. mccannii — detected near Cleveland, Ohio, in 2012. Has since spread east to the Atlantic Ocean, south to Virginia, north into Ottawa.
  • Phytophthora austrocedrii — detected in nurseries in Ohio and Oregon in 2024. Previously known from Argentina and in England and Scotland. At the latter location it is causing mortality of native Juniperus and introduced Cupressaceae. See here and here.

Most of these pathogens were unknown at the time they were discovered – because they were causing disease in the invaded ecosystems.

beech leaf disease symptoms in northern Virginia; photo by F.T. Campbell

In the Face of International Failures, How Can USDA’s APHIS Succeed?

When countries choose to prioritize preventing bioinvasions, they can impose more restrictive controls than those implemented by the WTO/IPPC system.  

I urge USDA to more proactively use its authority to protect America’s plant resources. In particular, I urge USDA leaders to use the NAPPRA authority more effectively and quickly. This allows the agency to temporarily prohibit importation of plants that host potentially damaging pathogens. ). https://www.aphis.usda.gov/plant-imports/nappra

We Americans can’t protect our forests from pathogens without APHIS responding more promptly to recent detections of pathogens in North America and on Pacific islands. Recent events are not encouraging.

The agency did undertake an analysis of Phytophthora austrocedrii after it was detected in nurseries in two states. Unfortunately, in my view, APHIS and the states decided the pathogen was too widespread so they dropped any idea of regulating it. This was despite the apparent threat to junipers across the country. See here and here. P. austrocedri also attacks cypress trees, including Port-Orford cedar, Chamaecyparis lawsoniana. USFS scientists recently announced success in breeding POC trees resistant to a different pathogen.    

There are no indications that APHIS will respond to detection of a new pathogen causing wilt disease in elms (Plenodomus tracheiphilus) recently discovered in Alberta, Canada. The pathogen is spread primarily through movement of infected plant material, including on asymptomatic material. Current U.S. regulations do not prohibit importation of plants or cut greenery in the Ulmus genus from Canada. Beyond the risk associated with elm material, I think it is probable that this pathogen also survives on plants in additional taxa, since it was formerly known for causing disease on citrus trees.

Although APHIS has classified Leptosillia pistaciae as a federal quarantine pest, I have learned of no response to detection of the pathogen on the native California shrub, lemonade berry (Rhus integrifolia), in 2019.

Rhus integrifolia – host of Leptosillia pistaciae

Has APHIS Changed its Practices in Response to Recent Detections?

We’ve known about gaps and weaknesses in APHIS’ approach for a long time. Here are specifics.

Has APHIS upgraded its attention to nematodes – as should have been prompted by detection of the beech leaf disease nematode (above)  and as recommended by Kantor et al.?

Has APHIS changed any of its practices or policies in response to detection of plant and human pathogens associated with wooden handicrafts from countries other than China? Or wood pieces used for unanticipated purposes, e.g., to decorate aquaria? All 31 fungal taxa detected by one of these studies were viable despite having been subjected to various phytosanitary requirements.   

USDA has no authority to regulate organisms that pose a risk to non-plant hosts, like us humans! Has APHIS contacted officials at the relevant agency?

Does APHIS respond to detections abroad when pests attack congeners of North American trees? I have blogged about several — see here, here, here and here — detected in Europe or Asia that attack cypress, magnolia, dogwood, Persea, and oaks. PestLens — an alert system created by APHIS — reported these.             

How has APHIS incorporated the findings at various “sentinel garden” projects? And the wider implications of findings by Eliana Torres Bedoya and Enrico Bonello regarding findings on asymptomatic plants?  

How is APHIS applying the impact assessment tools developed (for insects) by Ashley Schulz and Angela Mech? Has APHIS incorporated Kenneth Raffa’s advice about the strengths and weaknesses of various prediction tools?

I wonder whether APHIS has responded in any way to the rash of woodborer introductions on the west coast, including three species in the invasive shot hole borer complex and the Mediterranean oak borer. Has the agency explored the threat that the spotted poplar borer (Agrilus fleischeri) – another wood-boring beetle native to northern Asia – might pose to North American Populus species? Canada has twice intercepted the species on solid wood packaging material .  

USDA APHIS is explicitly not a research agency. However, it claims that its decisions are science-based. In my view, this means APHIS has a responsibility to respond to scientific findings (such as those  above) and to bring about research aimed at answering pertinent questions, e.g., those related to risks of pest introduction and establishment, effective detection and management technologies, etc.

APHIS has occasionally done this:

  • It established the NORS-DUC research facility to study what aspects of nursery management facilitate establishment of Phytophthora ramorum.
  • It enabled and participated in several studies of wood-borer introduction via wood packaging, including those by Robert Haack and colleagues (see blogs on this website under the category “wood packaging”).
  • It enabled and participated in a study of introduction pathways that included plants-for-planting – relying on 2009 data. (Liebhold et al. 2012)  
  • Did APHIS support the study by Li et al. to evaluate the vulnerability of two oak and two pine species to 111 fungi associated with Old World bark and ambrosia beetles?

APHIS could do much more to determine whether North American trees are vulnerable to pathogens and arthropods detected on the congeners in trade partner countries. Opportunities include:

  • studying which North American species might be vulnerable to the growing number of the 38 new Phytophthora species detected overseas. This would be a monumental task:  216 species have been recognized in the genus. I have focused specifically on the 38 species detected by Jung, Brasier, and others in Vietnam and now the 18 Phytophthora species detected in the Alps.  (I have already noted that APHIS and the states dropped any idea of regulating one of those species, P. austrocedrii).
  • Regarding P. ramorum specifically, scientists now recognize 12 genetic strains; 8 are in Southeast Asia, a ninth (EU2) in Europe. How likely is it that some of these will be introduced to the U.S.? Three strains are known to be established in western North American forests – NA1, NA2, and EU1.

In addition, new hosts continue to be identified. APHIS has pledged to update the host list annually. In the past I have criticized APHIS for not accepting hosts identified in the United Kingdom.

While APHIS is not well-funded, it has largely escaped budget slashing by “DOGE,” other Trump Administration cuts, and congressional decreases. Scientific expertise at the USDA Forest Service has been shrinking for decades (see Chapter 6). Now, loss of expertise has reached crisis levels. The result will be less capacity to assist APHIS in evaluating pest risks and research needs.

Earlier, I noted the importance of APHIS using its full NAPPRA authority.  Unfortunately, the record is not encouraging here, either.

Since the agency gained this authority in 2011, it has adopted lists of species temporarily prohibited for importation only three times – in 2013, 2017, and 2021. I complained that the last action was tardy and provided insufficient protection to Hawai’i’s unique flora arising from multiple strains of the ‘ōhi‘a rust pathogen Austropuccinia psidii and here. Even worse, four years after promising to close the loophole that allowed continued imports of cut flowers and foliage – the most likely pathway by which the rust was introduced to Hawai`i, APHIS has not proposed the necessary rule.

Pathogens are more difficult to detect and manage than invasive insects. The “disease triangle” is complex! Numerous pathways are involved! But they also get less attention – and this reflects unwise decisions by agency leaders. I suggest that they should respond to this complexity by adding resources. Voglmayr et al. (full reference at the end of this blog) also called for more attention to pathogens. Kantor et al. noted that nematodes are also neglected.

Of course, I have repeatedly urged APHIS leadership to enhance enforcement of regulations governing imports of wood packaging. One suggestion is that it prohibit importation of Chinese wood packaging  because of its 25-year record of not complying with – first – U.S. and Canadian regulations and – later – the international regulation known as ISPM#15.

Information Gaps Impede APHIS’ Domestic Program

I have criticized APHIS’ failure to find answers to several questions important to managing the sudden oak death pathogen, Phytophthora ramorum. Like the many questions listed earlier, these also need priority attention.

APHIS has regulated interstate movement of nursery stock to contain P. ramorum for over 20 years. I appreciate its creation of NORS-DUC. But it is also responsible for protecting natural systems in regions not yet invaded, e.g, in the East. APHIS should have studied these issues years ago, given the frequency with which pests spread nationwide via the nursery trade.

Other pathogen systems also have genetic variation that might be important in determining pest-host relationships. As of 2022, scientists had identified 43 haplotypes (genetic variants) of E. fornicatus s.s. worldwide, with the greatest diversity in several Asian countries (P. Rugman-Jones, pers. comm). Other species of plant pathogens also have several haplotypes. 

Forests At Risk Outside of North America

North American forests are not alone in being besieged by non-native pathogens. Their numbers have been rising also in Europe and Oceania. The record is less clear in Africa, South America, and Asia.

Reports of tree pathogens in Europe began rising suddenly after the 1980s – admittedly 15 years before the WTO took effect. By 2012, more than half of infectious plant diseases in Europe were caused by introduction of previously unknown pathogens  https://www.nivemnic.us/?p=5164

Antonelli et al. (full citation at the end of this blog) report that three previously undetected species of Phytophthora have been detected in European nurseries since 2016. Voglmayr et al. reported that the number of alien fungi in Austria increased 4.6-fold over 20 years. Eighty percent were plant pathogens. The introductory pathway was unclear for the vast majority. They note that differences in research efforts probably explain some discrepancies.

The ash decline pathogen, Hymenoscyphus fraxineus, has apparently been present in eastern Europe since the 1980s, so its spread has probably not been facilitated by the downsides of the WTO/IPPC system.

Other sources report recent introductions of insects to Europe. Musolin et al. reported that 192 species of phytophagous non-native insects had been documented in European Russia as of 2011. They included the emerald ash borer detected in Moscow in 2003. Some of these insects were probably introduced to Europe (outside Russia) before the WTO/IPPC system came into effect. Examples are two insects from North America that were detected in 1999 and 2000, respectively –  the western coniferous seed bug, Leptoglossus occidentalis, which vectors a pathogenic fungus Sphaeropsis sapinea (=Diplodia pinea); and the oak lace bug, Corythucha arcuata.

Australia was slow to respond to detection of myrtle rust, Austropuccina psidii. Few federal resources were made available to study its impacts – although the Australian flora includes at least 1,500 species in the vulnerable plant family. Carnegie and Pegg said this experience demonstrated the need to integrate the work of agencies responsible for conservation of natural ecosystems with those determining and implementing phytosanitary policy. New Zealand initially responded more assertively, but also found little funding to support resistance breeding or even to track the rust’s spread. 

The record is less clear regarding Africa, South America, and Asia.

Africa

Sitzia et al. expressed concern that bark and ambrosia beetles threaten to cause significant damage to tropical forests. Several factors contribute to these threats: the long history of plant movement between tropical regions; conversion of tropical forests that disturbs canopies, understory plant communities, and soils; and, generally, regions with fewer resources to prevent or respond to invasions.

In Africa, Graziosi et al. reported on the cumulative economic impact of invasive species and the continent’s limited capacity to prevent or respond to introductions. They don’t discuss whether pests attacking plantations of non-native trees followed those trees from their point of origin. They found that some introduced insects pose significant threats to native tree species. They mentioned the Cypress aphid, Cinara cupressi, which was attacking both native African cedar, Juniperus procera, and exotic cypress plantations. All the examples appear to have been introduced before the WTO/IPPC system took effect. All the examples appear to have been introduced before the WTO/IPPC system took effect.

Cinara cupressi; photo by Blackman & Eastop via Wikimedia

Graziosi et al. point out that South Africa plays a central role because it imports significant volumes of goods that can transport pests. At most immediate risk is South Africa’s highly diverse and endemic flora. For example Phytophthora cinnamomi is attacking native Proteaceae, which are important components of the unique Cape Floral Kingdom.  Other pathogens are attacking native conifers in the Podocarpus genus, Ekebergia capensis (Meliaceae), and Syzygium trees. However, pests first introduced to South Africa often spread. Graziosi et al. name several insects and pathogens of Eucalyptus and the wood-boring pest of pine Sirex noctilio.

Pests in Asia

Available information about China is not definitive. The FAO reports that half of the most damaging forest pests are non-indigenous. They were estimated to occur over an area of 1.3 million ha and to kill over 10 million trees per year. However, the three tree-killing pests which receive the most attention are the pinewood nematode (Bursaphelenchus xylophilus), red turpentine beetle (Dendroctonus valens), and fall webworm (Hyphantria cunea). These were all introduced before the World Trade Organization was founded.

The FAO notes several non-native insects that attack native trees in India, but all were introduced decades before the World Trade Organization began. There is no discussion of tree pathogens.

Thu et al. report a growing number of pest outbreaks damaging plantations of non-indigenous trees in Vietnam. In most cases the pests are indigenous to the country. They report that almost nothing is known about pests that attack species in the highly diverse native forests.

The September 2025 meeting of the International Forest Quarantine Research Group (IFQRG) had a session devoted to the topic “Risk of international trade in plants for planting”. The specific presentations are titled

  • “Using molecular tools to elucidate the pathways of cryptic pests on plants for planting”
  • “Risk-based approach to the movement of germplasm into Australia: the luxury afforded to an affluent continent” (note my earlier blog criticizing Australian efforts re forest pests)
  • “Challenges in the validation of methods for detection of quarantine pathogen – P. ramorum”
  • “Challenges in surveillance and detection of quarantine fungal tree pathogens in European Union”
  • “Pathogens in trade and the risk of establishment – update”

I hope that some of these discussions begin to tackle the crucial questions I raised in this blog and earlier. Also, I hope IFQRG continues to explore these important questions.

As Wu and Raffa et al. have said, Earth’s forests cannot afford delay in finding solutions to the challenges posed by introductions of novel pathogens to naïve systems.

SOURCES

Antonelli, C.; Biscontri, M.; Tabet, D.; Vettraino, A.M. 2023. The Never-Ending Presence of

Phytoph Spp in Italian Nurseries. Pathogens 2023, 12, 15. https://doi.org/10.3390/pathogens12010015

Voglmayr, H., A. Schertler, F. Essl, I. Krisai-Greilhuber. 2023. Alien and cryptogenic fungi and oomycetes in Austria: an annotated checklist (2nd edition). Biol Invasions (2023) 25:27–38 https://doi.org/10.1007/s10530-022-02896-2 

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

How do we prevent their introduction?

healthy eastern hemlock in Shenandoah National Park; photo by F.T. Campbell

PestLens reports newly detected insects and pathogens that seem to pose a threat to North American forests.

  1. Insects on hemlock – Tsuga spp

a) Adelges lepsimon (Hemiptera: Adelgidae) – found infesting Tsuga dumosa (Himalayan hemlock) trees in Bhutan.

b) bark beetle Pityokteines spinidens (Coleoptera: Curculionidae) – infesting Tsuga canadensis trees in an arboretum in the Czech Republic. Affected trees showed branch dieback, entry holes, and internal galleries.

Eastern hemlock has already been greatly reduced by hemlock woolly adelgid.

loblolly pine; photo by dcrjsr via Flickr

2. Several fungi infesting loblolly pine – Pinus taeda

needle chlorosis and drying, canopy dieback, and root necrosis on loblolly pines in Brazil is caused by the fungi Ilyonectria leucospermi, I. protearum, I. robusta, and I. vredehoekensis (Sordariomycetes: Hypocreales).

PestLens is supposed to alert APHIS to threats; I hope the agency is paying attention!

The USFS Southern Research Station reports that it is investigating brown spot needle blight, caused by the fungal pathogen called Lecanosticta acicola. The report says the pathogen has been present in the U.S. for more than 100 years, but does not indicate an origin. Other sources show it as widespread in both North America and Europe. The USFS notes two recent significant outbreaks, one affecting more than a million acres of loblolly pine in the Southeast, the second on eastern white pine in the Northeast. The pathogen also infects other species. .

You can subscribe to PestLens and receive weekly alerts – go to the website.

Posted by Faith Campbell

Y’all Come! National Plant Board Will Meet in Virginia in July 2026

The National Plant Board (NPB) represents the state officials responsible for preventing the introduction, establishment, and spread of invasive species called “plant pests” – including insects and pathogens that attack our native flora and invasive plants. The NPB has just held its 2025 meeting, on which I report here.

Coming to the Mid-Atlantic: NPB 2026 Annual Meeting

The next annual meeting will be in Alexandria, Virginia at the end of July 2026.I have attended these annual meetings since 2006 and always find them worth my time. They provide a wonderful opportunity to interact with the state and federal officials responsible for managing invasive plants and plant pests, and to assess regulatory issues. Contact me for more information.

The agendas focus on practical topics, such as science and technology tools, changes in APHIS policies or practices, and progress in cooperation among relevant federal agencies (i.e., the U.S. Department of Agriculture and the Department of Homeland Security’s Bureau of Border Protection) and with the states. While agricultural pest issues are stressed, tree-killing pests also get attention. Sometimes invasive plants are also discussed. The Board’s state representatives seek ways to coordinate their efforts both at these meetings and throughout the year.

Issues in the host location are part of the focus. Next year, that will be the Mid-Atlantic. The meeting is being co-hosted by the departments of Agriculture of Virginia, Maryland, Washington, D.C., and Delaware.

I expect that there will be opportunities for presenting concerns of non-governmental organizations – at least through staffed display tables and possibly other activities. I hope the many conservation organizations that have a Washington, D.C., presence will consider participating.

In Honolulu: NPB 2025 Annual Meeting

NPB’s 2025 Annual Meeting in Honolulu focused to some extent on the unique aspects of agriculture and introduced pests on remote Pacific islands. (Guam was co-host.) This blog reports on current efforts by federal and state authorities to counter bioinvasions there and around the country.

I took advantage of the meeting to visit the “Big Island” of Hawai`i to see for myself the impact of rapid ‘ōhi‘a death and enjoy the native flora (for example, the hapu tree fern – below). I posted another blog reporting what I learned there.

native Hawaiian tree ferns & ʻōhiʻa; photo by F.T. Campbell

Federal

In an earlier blog, I outlined the Administration’s proposed cuts to staff of the U.S. Department of Agriculture (USDA) and contradictory actions by Congress in the annual appropriations bills.

As that blog makes clear, the work of USDA’s Animal and Plant Health Inspection Service (APHIS) is viewed much more positively by the Trump Administration than is the USDA Forest Service. While APHIS’ funding is much more secure, staff cuts and reorganization of the USDA still have caused setbacks. APHIS is expected to lose 15% of employees – 1,180 people. Four hundred APHIS employees accepted the Administration’s deferred resignation offer. These included the leadership of many programs – including the previous Deputy Administrator, Mark Davidson. Higher up, no one has been appointed to the position of Deputy Secretary for Marketing and Regulatory Affairs.

In his report to the meeting, APHIS Acting Deputy Administrator for Plant Protection and Quarantine Matthew Rhoads noted that the Administration’s Farm Security Plan, which emphasizes efforts to combat bioterrorism, includes APHIS’ safeguarding role. However, abrupt and incomplete leadership changes hamper efforts to replace those who have left and set agency priorities. While I am cheered by the reported priority for preventing pest introductions, I fear that the focus might be quite narrow, leaving out threats to natural resources such as native forest trees.

Rhoads announced that after years of effort, the Asian longhorned beetle has been declared eradicated on 12.3 square miles of the Massachusetts quarantine zone.

Much of the presentation by Matthew Rhoads and later ones by other APHIS staff updated attendees on progress on technologies important in pest detection and control, and specific projects being carried out jointly by APHIS and NPB members (that is, state regulatory officials chosen to represent the state phytosanitary agencies). I consider the collaborative projects — begun in February 2023 – to be very important. Twenty years ago, relations between APHIS and its state counterparts were characterized by an “us vs. them” attitude.

I will summarize progress on the projects of greatest interest to those of us focused on non-native insects and disease pathogens threatening tree species. Rhodes mentioned improvements in the plant pathogen diagnostic certification program and development of improved molecular diagnostics for 45 insects and plant pathogens, including several Phytophthora species.

Joint APHIS-NPB teams have completed many risk analyses: 18 datasheets, 20 assessments, and four pathway analyses. As usual, insects – especially beetles – are the most numerous taxa detected. Many were surprised that the majority of new detections occurred in the south. When he was asked about this, Rhoads speculated that this reflected the region’s more hospitable climate and Florida’s surveillance efforts. I noted that ports in the southeast – e.g., Savannah and Charleston – are receiving higher import volumes; and that there have been problems with dunnage in the port of Houston.  

Large container ship docked at Port of Savannah; photo by F.T. Campbell

Rhoads praised the federal-state strategic alliance’s project targetting illegal importation of plants purchased on-line. His example should concern us: importation of as many as 10,000 black pine seedlings to Georgia. The state stopped sale of these plants and APHIS’ investigatory unit began an investigation. This example illustrates the volume of plants that might be moving in this trade. Several states asked APHIS to offer more help in countering trafficking involving smaller numbers.  All agree that no one has yet figured out an effective way to control this pathway.

A second example of successful coordination between APHIS and the states was said to be the decision to not regulate Phytophthora austrocedri, a pathogen detected in several nurseries in Oregon in 2024. Possible hosts in the Pacific Northwest include the already-depleted Port Orford cedar, and here; Juniperus californica, J. grandis, J. occidentalis, and J. maritima. Federal and state plant health officials, in coordination with the nursery industry trade association (AmericanHort), reached this decision after determining that the pathogen has probably been present in Oregon for many years and been spread to other states on the large volumes of host plants shipped. Now it will be up to states and non-governmental conservation organizations to try to detect whether this pathogen has established and devise management strategies.

New Information (as of December 2025): someone has posted on the web a written explanation of this decision by APHIS to the National Plant Board. [Visit cdn.ymaws.com, search for “Phytopthora austro”]. APHIS estimated that delimitation surveys in just one nursery would cost more than $9 million. Because the pathogen cannot be detected by visual symptoms, even tracking spread requires expensive destructive sampling of large numbers of plants. Meanwhile, thousands of possibly infected plants have been shipped from at least two Oregon nurseries in recent years. APHIS concluded that a Federal survey program for P. austrocedri would not contribute to ultimately controlling the spread or eradication of this pathogen. The agency recommended instead that natural resource agencies adopt a “protective-style approach”, focused on actively managing highest-value natural sites.  

Are federal, state, and non-governmental managers of the many types of ecosystems inhabited by junipers and cypresses equipped to do this?

Ordinarily, the USFS Forest Health Protection program would be in a position to assist states which want to manage this pest (assuming its establishment). But considering the current uncertainty regarding USFS’ future, blog states cannot count on that help.

Sky Stevens (entomologist on the staff of USFS Forest Health Protection program) reported on the situation at the USFS. She noted that the Congressional appropriations bills continue funding for the agency’s research program and collaboration with non-federal entities managing forests. Still, the USFS lost 5,200 people through “voluntary” resignations and firings.

The program of greatest importance to us, Forest Health, was cut from 18 people to 8. Stevens replaced the long-time national entomologist. The comparable pathologist has retired. Stevens is struggling to make decisions regarding the pathology program, especially since diseases are inherently more difficult. While the USFS is doing lateral exchanges to fill high-need vacancies, FHP has not yet been asked what the program needs.

According to Stevens, in 2024 about 9 million acres were impacted by forest pests. The FHP program treated 1 million acres. As usual, the (European) spongy moth was the largest target based on acreage. Other non-native species targetted were emerald ash borer, goldspotted oak borer, sudden oak death, Asian longhorned beetle, hemlock woolly adelgid, and rapid ‘ōhi‘a death. See summaries of these pests’ impacts and status here.  

Continuation of these projects in 2025 often became trapped in the new Administration’s funding freezes; opportune times for effective actions were often missed. On-going projects include several targetting emerald ash borer and its hosts in Oregon and black ash swamps of the Midwest and Northeast; managing sudden oak death in Oregon and California; and delimitation surveys for rapid ‘ōhi‘a death.  The SOD program benefits from approximately $3 million earmarked by Congress (out of the total funding for the forest health program of $48 million).

Stevens noted that it is difficult to discuss the program’s future given the uncertainty. Program staff hope to continue issuing products that help people understand forest health in their region – not limited to federal lands.

I learned from the review of the following programs and technical tools that many were funded by the grant program under APHIS’ Plant Pest and Disease Management and Disaster Prevention program  (Plant Protection Act Section 7721). Clearly, America’s efforts to prevent and respond to invasions by plant pests (including invasive plants) would be far less robust without this grant program.

boxwood (box tree) garden at Gunston Hall – an 18th Century plantation near Alexandria, Virginia (site of the 2026 NPB meeting); Photo by Roger 4336 via Wikipedia

Wendy Jin, APHIS PPQ Associate Deputy Administrator, urged states to use pest forecast models developed under the SAFARIS program. These models incorporate information on weather; pest biology, environmental needs and impact; hosts; land cover; and relevant human activities. Fifty pests have been evaluated so far, apparently including Asian longhorned beetle, spongy moth, spotted lanternfly, and boxtree moth. (All but the last are described briefly under the “invasive species” tab here.) The goal is to provide managers information about the insect’s life stage at specific times in specific localities so that they can time their surveillance and management actions. However, I am somewhat worried because the models use current and historical weather data – which might not be pertinent as the climate warms. Worse, the modelers lack sufficiently detailed data to develop models for Alaska, Hawai`i, Puerto Rico, or Guam.

Dr. Carrie Harmon (Deputy Director, National Plant Diagnostic Network) described the resources available for states use from two diagnostics tools. Both were developed under grants which are now expiring. Therefore updates and further development will depend on renewal of the grants.  The National Plant Diagnostic Network (NPDN) provides accurate data and alerts about appearances of plant diseases. APHIS is said to be collaborating closely to ensure as much data as possible is shared. A separate body, the Diagnostic Assay Validation Network, is validating diagnostic assays.

A few years ago the NPB and APHIS formalized their new level of collaboration as the “Strategic Alliance, Strategic Initiative”. The Plant Board surveyed its members to gauge their feelings about several issues: 1) data-sharing issues that impede decision-making; 2) ways to strengthen coordination when dealing with on-line sales of plants or other vectors of plant pests (see the pine-Georgia example above); and 3) what structures and practices could make resolving these problems easier. 

One of the resulting initiatives is an analysis of implementation of the Federal Noxious Weed program in the absence of a line-item appropriation. However, the President’s “Department of Government Efficiency” (DOGE) prompted resignations and firings, including this project’s APHIS liaison. Without a replacement, it is unclear how the analysis can proceed.

Another speaker, representing Bob Baca, Assistant Director of APHIS Plant Protection and Quarantine, warned state officials about new pressure to phase out use of methyl bromide (MB) as a phytosanitary tool. Use of ozone-depleting chemicals – including MB – has been regulated since 1988 under the Montreal Protocol. Americans use more MB for this purpose than any other country. Already manufacturers are ending its production. After mentioning substitutes under development, the speaker urged state departments of Agriculture to meet with growers and develop a nation-wide plan to weather this impending change. She noted that APHIS has no authority to require companies to produce substitutes. 

The NPB leadership discussed turnover in the organization (several states are represented by officials new to their jobs); advocacy to APHIS for even better coordination and recognition of states’ need to act quickly; and efforts to expand its collaboration with other entities. A series of presentations tallied lessons learned during specific plant pest crises. These included the role of the public in pest detection; mobilizing initial responses to a new pest; and building higher-ups’ and legislators’ support for funding a “rapid response” capability before arrival of a new damaging pest.

In a separate blog I reviewed topics discussed that pertain particularly to Pacific island plant health issues.

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

Or

https://fadingforests.org

Status of Hawaiian species threatened by bioinvasion

stand of Miconia under albizia overstory on Big Island, Hawai`i; photo by F.T. Campbell

As I will describe in another blog, participants in the annual meeting of the National Plant Board link in Honolulu learned the basics about the uniqueness of agriculture and native species on remote Pacific islands. I want to complement this information by reminding you about other Hawaiian and Guamaian species at risk – although did not learn anything new.

As Martin and Andreozzi pointed out, the Pacific islands import nearly all their food and other consumables. Considerable interest in some quarters in Hawai`i to increase agricultural production. However, large swaths of land in the low-elevation area surrounding Pahoa on the Big Island is completely dominated by the albizia (Falcataria Molucca) [see photo above]. J.B. Friday says it is cost-prohibitive to remove these trees in order to restore agriculture in the area. Local people are concerned because in storms the trees fall onto houses and roads, causing considerable damage.

I saw numerous clumps of the notorious invasive plant Miconia calvescens. Dr. Friday told me that conservationists now focus on keeping this plant out of key areas, not trying to eradicate it completely.

area being restored by volunteers; photo by F.T. Campbell

Local people trying to restore disease-damaged forests by planting other native plants and hand-clearing invasive plants. Some of the ohia seedlings infected by Austropuccinia psidii.

ohia seedling with symptoms of ohia rust (Austropuccinia psdii); detected by J.B. Friday; photo by F.T. Campbell

Dr. Friday showed me many areas where ʻōhiʻa trees have been killed by rapid ʻōhiʻa death. Since this mortality occurred a decade or more ago, other plants have grown up. Pic  In many if not most cases, this jungle includes dense growths of guava Latin the most widespread invasive tree on the islands (Potter). ‘Ōhi‘a trees continue to thrive in Hawai`i Volcanoes National Park – also on the Big Island – because the NPS makes considerable efforts to protect them from wounding by feral pigs. Demonstrates importance of fencing and mammal eradication in efforts to protect this tree species.

healthy ʻōhiʻa tree on cinder cone created by eruption of Kilauea Iki in 1959; photo by F.T. Campbell

I also saw healthy koa (Acacia koa) in the park, especially at sites along the road to the trail climbing Mauna Loa.

Regarding the wiliwili tree, I was told that it remains extremely scarce on Oahu.

wiliwili tree in flower; photo by Forrest Starr

I heard nothing about the status of naio – another shrub native to the Big Island – but on the dry western side of the island.

I rejoice that scientists are making progress in protecting and restoring Hawaii’s endemic bird species. Specifically, they are at the early stages of controlling mosquitoes that transmit fatal diseases. All 17 species of endemic honeycreepers that have persisted through the 250 years since Europeans first landed on the Islands are now listed as endangered or threatened under the federal Endangered Spp Act. The “Birds, not Mosquitoes” project has developed lab-reared male mosquitoes that, when they mate with wild female, the resulting eggs are sterile. (Male mosquitoes don’t bite, so increasing their number does not affect either animals or people.) Over time, the invasive mosquito population will be reduced, giving vulnerable native bird populations the chance to recover. Scientists began releasing these modified mosquitoes in remote forests on Maui and Kaua‘i in November 2023. In spring 2025, they began testing releases using drones. Use of drones instead of helicopters reduces the danger associated with flying close to complicated mountain rides in regions with variable weather.   This project should be able to continue; the Senate Appropriations Committee report for FY26 allocates $5,250,000 for this project.

American Bird Conservancy is sponsoring a webinar about this program. It will be Wednesday, August 27, 2025 4:00 PM – 5:00 PM ET. Sign up for the webinar here

thicket of guava on the Big Island, Hawai`i; photo by F.T. Campbell

Finally, scientists are releasing a biocontrol agent targetting strawberry guava, Psidium cattleyanum, the most widespread invasive tree on the Islands (Potter et al. 2023). Distribution involves an interesting process. A stand of guava is cut down to stimulate rapid growth. The leaf-galling insect Tectococcus ovatus reproduces prolifically on the new foliage. Twigs bearing the eggs of these insects are collected and tied into small bundles. The bundles are then dropped from helicopters into the canopies of dense guava stands, where they establish and feed – damaging the unwanted host.  

brown tree snake; photo via Wikimedia

Guam

Guam’s endemic birds have famously been extinguished by the non-native brown tree snake. Dr. Aaron Collins, State Director, Guam and Western Pacific, USDA APHIS Wildlife Services, informed participants at the National Plant Board meeting about the extensive efforts to suppress snake populations in military housing on the island, reduce damage to the electric grid, and prevent snakes from hitchhiking to other environments, especially Hawai`i and the U.S. mainland.

The program began more than 30 years ago, in 1993. The program now employs 80 FTEs and has a budget of $4 million per year. It was initiated because live and dead snakes had been found in shipments and planes that landed in Hawai`i and the U.S. mainland. Avoiding the snake’s establishment on Hawai`i is estimated to save $500 million per year. The program is a coordinated effort by USDA, U.S. Fish and Wildlife Service, and the Department of Defense. Probably this estimate helped advocates reverse a decision by the “Department of Government Efficiency” to defund the program.

The program enjoys some advantages over vertebrate eradication programs on the mainland. For example, since Guam has no native snakes, it can use poison, e.g., in mouse-baited traps that can be dropped from planes. A recent innovation is auto-resetting traps baited with mammals; they can electrocute numerous snakes per night.

SOURCE

Potter, K.M., C. Giardina, R.F. Hughes, S. Cordell, O. Kuegler, A. Koch, E. Yuen. 2023. How invaded are Hawaiian forests? Non‑native understory tree dominance signals potential canopy replacement. Lands. Ecol. https://doi.org/10.1007/s10980-023-01662-6

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

Or

https://fadingforests.org