plants as pest vectors – Page 3 – Center for Invasive Species Prevention

Integrating Invasion & Phytosanitary Sciences & Practice

vegetation killed by *Phytophthora cinnamomi* in West Australia

Some invasive species practitioners have been trying to develop a standardized framework for describing bioinvasions. Their goal is to overcome disparities in approaches developed by scientists working with various taxonomic groups in hopes of improving understanding of, and communication about, bioinvasions. Prominent among these efforts is the “Unified Framework for Bioinvasion” published by Blackburn et al. in 2011 (full citation at end of blog).

Now several forest pathologists (Paap et al; full citation at end of blog) say that this framework does not adequately integrate forest pathogens. This omission is particularly unfortunate given the prominence of forest pathogens as damaging invaders – e.g., chestnut blight in Europe and North America; white pine blister rust in North America; sudden oak death in North America and Great Britain; myrtle rust and Phytophthora cinnamomi in Australia. (See profiles of all these pathogens here; I note additional examples in North America, such as laurel wilt disease.)

Paap et al think that this omission impedes understanding of both forest pests and invasive species in general. Also, they say that integrating microorganisms into the broader Blackburn framework would help forest pathologists better understand how and why invasions occur, where they occur, and how they can be stopped or mitigated.

Furthermore, they note the importance of integrating the diverging terminologies used by invasive species practitioners and plant pathologists and their separate regulatory bodies – the Convention on the Conservation of Biological Diversity (CBD) and the International Plant Protection Convention (IPPC). I concur, since nations’ programs regulating plant diseases and their vectors operate under the IPPC rubric.

Figure 2 and Table 1 lay out Paap et al.’s proposed modification of Blackburn’s framework, and detail strategies linked to management goals appropriate for the stages of plant disease development.

Tanoak mortality in southern Oregon caused by *P. ramorum* – a pathogen completely unknown until it was introduced to North America and Europe; photo by Oregon Department of Forestry

However, such integration will be impeded by many difficulties (I have re-ordered these points):

1) The first – which underlies all others — is the paucity of data on microbial taxa, which undermines the pest risk analyses and other systems developed for assessing and managing other types of invasive species. That is,

Many of the vast number of microbial taxa have not yet been described.
Even species that have been describe often cannot be ascribed to a specific geographic origin. This information gap undercuts efforts to determine whether a disease outbreak is caused by an “introduced” organism.

2) Microbial species are usually detected only when disease impacts become obvious. However, an outbreak might not signal a new or spreading “introduction”. While invasive species must—by definition—cross a geographic boundary (through the assistance of human actions), pathogens can cause disease outbreaks through breaching a wider range of boundaries, including ecological and evolutionary ones. Thus, the disease outbreak doesn’t always fit the definition of “invasive species”.

3) Substantial differences exist in training and goals between fields. Forest pathologists are usually trained in plant pathology (often focused on crops) rather than in forestry or ecology. Their goal is to manage the pathogen. Invasion scientists tend to focus on natural ecosystems, study animal and plant invasions, and seek understanding of the invasion process.

4) A related issue is that the two fields operate under separate regulatory bodies that have different emphases and aims. Paap et al. note that while the IPPC ostensibly includes impacts on natural environments, its members’ priority is plants of economic importance. The World Trade Organization’s Agreement on the Application of Sanitary and Phytosanitary Measures (WTO SPS) seeks primarily to minimize disruption of trade resulting from plant health regulation. On the other hand, the CBD explicitly considers invasive species’ impact to the natural environment (Aichi Biodiversity Target 9). [To read my critique of the WTO SPS and IPPC, read the Fading Forests reports (link at end of this blog), especially FF II.]

They note that in 2004, the IPPC and CBD secretariats established a Memorandum of Cooperation to promote synergy and to avoid duplication. Paap et al. appear disappointed that despite development of joint work plans, phytosanitary programs are still focused largely on crop pathogens.

Disease development – a complex set of circumstances that makes risk assessment less reliable

Since I am not a pathologist (or even a biologist), I learned a lot about the complexities of plant pathology from Paap et al.

While I am certainly familiar with the “disease triangle” concept, I had not thought about certain implications. For example, pathogens can cause severe disease outbreaks by evading any one of three types of barriers: geographic, environmental, or evolutionary. Transport of the micro-organism to a new ecosystem (leaping the geographic barrier and meeting the definition of an “introduction” in invasive species terminology) certainly can facilitate disease outbreaks. However, evolutionary and environmental barriers might also be overcome in other ways.

The result is that a plant disease can develop under multiple scenarios following the introduction of an alien pathogen. These scenarios are:

disease on a coevolved host growing as an alien species in the new environment, for example plantations of trees grown for timber (pathogen reunion);
disease on a naïve host that is itself alien to the geographic region in question (host jump);
disease on an alien host (naïve or coevolved) which supports disease on a host native to the new geographic area that could not be sustained in the absence of the alien host;
disease on alien and native hosts; and
disease on a host native to the new geographic area but not on an alien host.

Countries’ efforts to conduct pest risk analyses are unlikely to be straightforward – or even possible – with so many disease scenarios

Paap et al. proceed to compare introductory pathways under the CBD categorization and plant pathology. In doing so they point out several aspects of introduction, establishment, and spread that are specific to pathogens. For example, trees’ long life spans and inability to adapt as rapidly as the micro-organism increase their vulnerability to devastating disease outbreaks following the arrival of a novel pathogen.

Participants in the Montesclaros meeting that drafted an early critique of international phytosanitary procedures

Paap et al. reinforce points made by other critics of current phytosanitary programs. (See my earlier blogs under the category “plants as pest vectors”.) In particular, they point out the weakness of visual inspection and note that new molecular assays can detect only known microorganisms. An additional complication is that DNA can persist in soil and plant tissue after death of the organism, leading to false positives. RNA is cannot yet be used as a viability marker.

Paap et al. provide three case studies to illustrate in greater depth several major challenges encountered when managing invasive forest pathogens. Most of these weaknesses are well known to forest pathologists.

1. The inconspicuous nature of microorganisms

As noted by Paap et al. and other authors, the difficulty detecting microbes is exacerbated by the huge volumes of goods, especially live plants, in international trade; the small proportion of those plants that can be inspected; the weakness of visual examination; application of fungicides and fertilizers before export that suppress symptoms. The chosen example is the oomycete genus Phytophthora, specifically P. ramorum.

2. Cryptic status of many species

Current biosecurity programs rely on naming the organism and its place of origin. This is actually impossible for many microorganisms. The tardy response to ash dieback (Hymenoscyphus fraxineus) in Europe illustrates the delay in determining the causal agent and its geographic origin. During this nearly two-decade period the possibility of preventing spread was lost.

3. Rapid evolution

Rapid evolution of the introduced pathogen can overcome resistance in a host. The example described is Cronartium ribicola (causal agent of white pine blister rust) on Western white pine (Pinus monticola) and sugar pine (P. lambertiana). They also mention the threat from hybridization between previously isolated populations, specifically Phytophthora x alni causing a devastating decline of black alder in Europe.

Sugar pine in Sequoia National Park; photo by S. Rae via Flickr

Paap et al. call for increased research to increase our knowledge of microbial diversity, especially in taxonomically rich and poorly studied ecosystems. They praise sentinel plantings as a powerful tool for early warning of pathogen threats.

SOURCES

Blackburn, T.M., P. Pysek, S. Bacher, J.T. Carlton, R.P. Duncan, V. Jarosik, et al. A proposed unified framework for biological invasions. Trends Ecol Evol. 2011; 26(7):333-9.

Paap, T., M.J. Wingfield, T.I. Burgess, J.R.U. Wilson, D.M. Richardson, A. Santini. 2022. Invasion Frameworks: a Forest Pathogen Perspective. FOREST PATHOLOGY https://doi.org/10.1007/s40725-021-00157-4

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

British & Irish Efforts to Prevent or Combat Pathogens

I often blog about the forest pest situation in the UK because its scientists provide lots of easily accessible information. This blog has new information on Britain and – I am pleased to add – on Ireland!

European ash trees alongside the Malham Cove path in Yorkshire; KA via geograph

UK Overview

British woodlands cover just 13% of total land area (just over one-third of the European average of 37%). Their value is increasingly recognized—especially their role in combating climate change through carbon sequestration, flood mitigation and urban cooling. Realization of these benefits is driving new policy to increase woodland cover. In 2019–2020, 13,700 ha of new woodland was created in the United Kingdom (Green et al. 2021). The U.K. government has pledged to plant 30,000 ha of broadleaf and coniferous woodland every year as part of its climate change mitigation strategy (Donald et al. 2021). One example, the ‘northern forest’ scheme, involves planting 50 million native trees over 25 years (Green et al. 2021).

Risks Associated with Conservation Plantings or Translocations

On-going conservation planting efforts plus these ambitious new plans prompted Donald et al. (2021) to assess risk that pathogens might be introduced into the environment as a result of putting native plants in natural habitats. The focus of their study is the planting of common juniper (Juniperus communis)in habitats throughout England, Scotland, and Wales.

Juniper killed by *Phytophthora austrocedri*; photo from British Forest Research

Juniper is one of three native conifers in the UK. It has been in decline for decades, which conservationists hope to reverse. Now, though, juniper populations are experiencing significant mortality from disease. In 2012, the causal agent was determined to be the non-native pathogen Phytophthora austrocedri. The presence of a single genotype in ~60 geographically separate locations across Scotland and England lends support to idea that the pathogen is being introduced to these sites through some human mechanism. Phytophthora austrocedri has not [yet] been detected in Northern Ireland.

British and European nurseries have contained many Phytophthora pathogens. Hence Donald et al. (2021) sought to determine whether the pathogen is being introduced through use of nursery stock in these well-intentioned plantings. (I have blogged about a similar problem in California restoration plantings.)

The authors found that 19% of P. austrocedri detections are within 2 km of a known planting. The more frequently junipers were planted at a site, and the more cuttings planted during each planting effort, the higher the likelihood that nearby junipers would be infested by P. austrocedri. They conclude that transplanting material is a significant risk pathway for the introduction of disease. The key factor appeared to be the origin of the material. A higher percentage of stock at sites with P. austrocedri outbreaks for which data were available had been raised in a central location by the organization doing the planting or obtained from commercial nurseries. No P. austrocedri was detected in Wales. There, unlike in Scotland or England, the majority of plants were sourced from a commercial nursery that only grew juniper collected from Welsh populations and did not trade with other retailers.

Planting juniper has risen rapidly since the mid-1990s. The highest percentage of planting events co-occurring with disease outbreaks were conducted in 2000–2009. It is likely that there is a time lag between planting and disease detectability. If so, the even larger planting effort since 2010 probably will produce many more P. austrocedri outbreaks that will become visible in the future. And that might not be the end. Planting guidelines have been revised based on pathogen detection. However, the entities doing the planting have not changed their approach, especially regarding site selection.

Donald et al. (2021) also found serious data gaps in these programs beyond the health of propagules. They found:

1) very incomplete knowledge of which organizations are doing the planting;

2) poor attention to traceability of source material; and

3) very little follow-up to check the success of planting projects.

The authors concluded that planting projects have had mixed success in restoring juniper populations. They called for changes in planting strategy to reduce the risks of pathogen introduction.

They also note that efforts to slow the spread of P. austrocedri – for which there is no treatment – are more expensive and less likely to succeed than measures aimed at ensuring that nurseries are free of Phytophthoras. California native plant nurseries have shown that nurseries can maintain Phytophthora-free stock.

Risk of Nursery-spread Pathogens & Willingness of UK Nurseries to Adopt BMPs

Great Britain has experienced an accelerating series of Phytophthora outbreaks and disease epidemics affecting British trees. Introductions detected just since early 2000s include P. ramorum, P. kernoviae, P. lateralis, P. austrocedri and P. pseudosyringae. In all the above cases, imported planting material either is confirmed or strongly implicated as the likely route of intro (Green et al. 2021).

To address this threat – and with massive planting projects proposed – in 2016 the British forest research entity initiated the multidisciplinary ”Phyto-threats” project. Its goal was to understand the drivers of rising Phytophthora infestations and opportunities for mitigating them. The project:

(i) examined Phytophthora distribution and diversity in different nursery management systems;

(ii) assessed the social and economic feasibility of a nursery accreditation programs to curb the risk; and

(iii) identified Phytophthora risks by modelling introduction, establishment and spread of species in relation to biological characteristics, environmental factors and trade flows.

The assessment of Phytophthora presence in nurseries involved collecting 3,624 water and root samples from 163 host genera growing in plant nurseries across the U.K. over a three-year period. Sampling was not random but targetted to facilities thought to harbor Phytophthora. About half of the samples tested positive. They identified 63 species of Phytophthora. Among the most commonly detected species are several that are considered pathogenic — P. cinnamomi, P. cryptogea/pseudocryptogea, P. syringae, P. cactorum, P. cambivora, P. plurivora and P. nicotianae. P. ramorum was found in 12 samples; P. lateralis and P. austrocedri were each found in 10 samples. Several Phytophthora species are potential new records for the U.K. (i.e., P. castanetorum, P. palmivora, P. pseudotsugae,P. tentaculata,P. terminalis, P. uliginosa).

They also saw evidence for Phytophthora root infections in newly arrived plants imported from the European Union.

Their finding raised question about whether Phytophthora can be transported in peat-free potting media, that is, coconut fiber or coir.

The widespread presence and the diversity of Phytophthora found in nurseries was linked to high-risk management practices. These included: careless disposal of culled plants, the near presence of trees along nursery boundaries, and, especially, open water sources. [These factors are essentially identical to infection-facilitating factors found by researchers in California, Oregon, and Washington State. See advisory issued by Oregon State University Extension.]

The project also assessed the feasibility of nursery accreditation programs. The authors consulted widely with nursery owners and customers and conducted a cost-benefit analysis. Regarding nursery practices, owners claimed they were already addressing issues related to water storage in enclosed tanks, clean/covered storage of growing media, installation of drains or free-draining gravel beds, raised benches, and tool disinfestation stations. Therefore the new analysis focused on seven other topics: water testing for pathogens; water treatment s; quarantine holding areas for imported plants; composting or incineration of culled plants; boot and vehicle washing stations; and purchase from only trusted or accredited UK suppliers.

The study found that nurseries would support an accreditation program. However, their support required that costs not be “prohibitive”, actions required not be “unreasonable”, the scheme provide a safety net; and that measures exist to deter non-compliance. Nursery staff wanted to see evidence of consumer demand – a willingness to drive farther to buy “clean” plants, or to pay higher prices for them. The cost-benefit analysis reached a worrying conclusion: nurseries would benefit financially from introducing best practices only when the program would prevent introduction of a wider range of pests and pathogens, not only Phytophthoras. Green et al. (2021) note that the overall net benefit to society from nurseries adopting best practices would be much more substantial. That is, healthy trees are important in meeting carbon sequestration goals. They did not explore whether society should subsidize nurseries’ participation in BMP accreditation programs.

Ireland and Northern Ireland

The island of Ireland (Ireland and Northern Ireland) is thought to have fewer plant pests than other European countries due to its island status and because of its national and international phytosanitary regulations. O’Hanlon et al. (2022) do not mention another possible factor: the likelihood that import volumes to Ireland were probably much lower until the recent vitalization of the Republic’s economy.

O’Hanlon et al. (2022) sought to establish baseline information so scientists can track changes as trade increases and the climate changes. Their search of the literature and unpublished sources identified 396 forest pests on the island, including 11 bacteria, 20 oomycetes, 150 fungi and 215 arthropods. They believe these figures are all probably underestimates. At least 44 of the pests or pathogens are probably non-native to Ireland. (Determining original ranges is difficult, especially for pathogens.)

The Republic of Ireland is one of the least forested countries in Europe. Forests cover ~ 11% of the land area. In Northern Ireland, it is even less: ~ 8%. These forests are predominantly plantations of exotic species. In the Republic, Picea sitchensis makes up 51% of the forest area, Pinus contorta another 10%. Other exotic species planted are Picea abies (4%) and Larix kaempferi. In Northern Ireland, ~ 62% of the forest area is composed of conifer mixtures. Planting of P. sitchensis has accelerated recently, probably as a result of removal of ash and larch because of their vulnerability to pests already established on the island.

Sitka spruce plantation in U.K. Adam Ward, Geograph.org.uk

O’Hanlon et al. (2022) note the great vulnerability of these monocultures to pests. They found 51 pests native to Ireland that are associated with non-indigenous tree genera. They are also concerned about pests introduced from other parts of Europe. For example, green spruce aphid (Elatobium abietinum, native to Central and Eastern Europe) is already attacking Sitka spruce. A second pest of spruce, Ips typographus, which is native to much of Europe but not the British/Irish isles, is not yet established on the island. Northern Ireland imports bark and wood from Europe for processing. Ips typographus has been associated with at least one such shipment.

Non-native forest pests and pathogens also threaten tree species native to Ireland. These include:

Dutch elm disease caused by fungi from the genus Ophiostoma vectored by bark beetles of the genus Scolytus. The second outbreak, caused by the more aggressive pathogen 0. novo-ulmi, was detected in Britain in 1965 and in Ireland in 1977. It caused considerable mortality of elms in Northern Ireland throughout 1970s.

Phytophthora ramorum was recognized as a threat to forests in Europe only in 2010, when extensive mortality of Japanese larch was detected in Britain. The Republic of Ireland has only the EU1 lineage of the species. Northern Ireland has both the EU1 and EU2 lineages – the former only in nurseries.

Phytophthora disease of alder (caused by several Phytophthora species) was confirmed in Ireland in 2001. However, symptoms of the disease were noted as far back as 1995. It is likely that there are many other Phytophthora species present but not yet recorded.

Ash dieback disease (causal agent Hymenoscyphus fraxineus) on European ash (Fraxinus excelsior) has spread across Europe from Poland beginning in the 1990s. It was confirmed on the Irish island in 2012. Authorities made significant attempts to eradicate the disease, but were not successful. It is now recorded in every county in both Northern Ireland and Ireland. Damage to the economy, environment, and society are expected to be large. The Irish government had helped plant more than 13,000 ha of ash between 1992 and 2012. An estimated 2.9 million ash trees are in Northern Irish hedgerows. British scientists say more than 1,000 fauna species are associated with ash trees.

A second pest on ash — ash sawfly (Tomostethus nigritus) — was detected in Northern Ireland in 2016; it has defoliated hundreds of trees in Belfast.

In recent years, forest pest incursions have increased at a relatively steady rate, comparable to other countries, including Britain. In the 1970s, 26 species were reported; in the 1980s, 27; in the 1990s, 16; in the 2000s, 37; between 2010 and 2017, 28. See the graph in Fig. 2

There is a strong link between pest and pathogen findings in Britain and Ireland. O’Hanlon et al. (2021) list 16 insects and pathogens detected in Britain after 1960 which were later detected in Ireland. The list includes H. fraxineus, 0. novo-ulmi, Phytophthora ramorum, and Phytophthora lateralis. The average delay was 10 years. The authors note that the two islands share similar ecological conditions and hosts, are nearby, plus there is substantial travel and exchange of goods between them. For example, in 2018 an estimated 30,000 metric tonnes of conifer roundwood was sent from Scotland to Northern Ireland for processing.

There are very limited physical checks on plants or plant products moving between Ireland and Northern Ireland. The exception is conifer wood that is not bark-free. European Union regulations require that such shipments be accompanied by a plant passport that certifies that the wood has been inspected by a professional operator authorized by the NPPO of the exporting country. What rules will apply now, after BREXIT, remains unclear. Because of concerns about re-igniting sectarian conflict, most political figures want the border on the island to be almost invisible.

The Europhyt database for the period February 2006 – November 2016 documented interception of numerous high-risk pests at the British and Irish borders, including Anoplophora chinensis and A. glabripennis; I. typographus; Monochamus alternatus; H. fraxineus; and P. ramorum O’Hanlon et al. (2021). believe many more go undetected. O’Hanlon et al. (2021) report specifically on detections on commodities from China, especially on wood packaging. One detection on imported plants of interest to me is that of Discula destructiva (dogwood anthracnose). The article does not mention the origin of the shipment. The native British dogwood, Cornus sanguinea, would presumably be vulnerable to this Asian fungus, which has already caused widespread mortality of woodland dogwoods in North America.

*Cornus sanguinea*; photo by Hans Hillewaert

In addition to reviewing the current situation, O’Hanlon et al. (2021) note pertinent facts about current policy and future science. First, while the two political units on the island have a history of plant pathology expertise, there has recently been a reduction in the number of practicing forest pathologists, mycologists and entomologists. (I and others have complained about the same deterioration in expertise in the United States.)

Second, they describe the years of delay before official recognition that the pathogen Gremmeniella abietina was present in Northern Ireland. This delay resulted from officials refused to accept data from molecular detection tools.

O’Hanlon et al. (2021) add their voice to others criticizing the international phytosanitary system (they cite six major publications: Brasier 2008; Liebhold el. al. 2012; Santini et al. 2012; Eschen et al. 2015; Jung et al. 2016; Meurisse et al. 2019). The failures are (i) visual inspections can miss asymptomatic infections, (ii) limited resources mean only a small proportion of commodities can be inspected, (iii) allowing the use of fungicides masks disease symptoms on plants, (iv) list-based regulations don’t address undescribed organisms and (v) countries vary in how aggressively they carry out the required phytosanitary procedures. O’Hanlon et al. (2021) conclude that “Until these issues are addressed it is likely further increases in the numbers of non-native pests and pathogens of trees will increase.”

The authors note that Eschen et al. (2018) suggested that risk analysis should focus on the commodity (commodity risk assessment) rather than on an individual pest. I have made a similar suggestion, although less clearly worded.

Finally, O’Hanlon et al. (2021) note that climate change is expected to increase the island’s vulnerability to tree-killing pests and pathogens due to fewer frost days, more rain in winter, increased chance of drought in summer, increased average annual temperatures, and more frequent weather extremes. These changes are likely to affect the amount of damage caused by both native and introduced pests organisms. Range shifts in both pests and pathogens and their natural enemies; physiological or behavioral responses in the pests; phenological changes in the hosts; and increased stress on the trees will combine to affect damage.

SOURCES

Donald, F.; Purse, B.V.; Green, S. 2021. Investigating the Role of Restoration Plantings in Introducing Disease—A Case Study Using Phytophthora [UK] Forests 2021, 12, 764

Green, S., D.E.L. Cooke, M. Dunn, L. Barwell, B. Purse, D.S. Chapman, G. Valatin, A. Schlenzig, J. Barbrook, T. Pettitt, C. Price, A. Pérez-Sierra, D. Frederickson-Matika, L. Pritchard, P. Thorpe, P.J.A. Cock, E. Randall, B. Keillor and M. Marzano. 2021. PHYTO-THREATS: Addressing Threats to UK Forests and Woodlands from Phytophthora; Identifying Risks of Spread in Trade and Methods for Mitigation. Forests 2021, 12, 1617 https://doi.org/10.3390/f12121617ý

O’Hanlon, R., Ryan, C., Choiseul, J., Murchie, A.K. and Williams, C. D. 2021 Catalogue of P&P of trees on the island of Ireland. Biology and Enviro

Proceedings of the Royal Irish Academy 2021. Vol. 121, No. 1.12-45 DOI: 10.3318/ BIOE.2021.02

Posted by Faith Campbell

Forest Pests: What’s Improved, What’s Still to Do

sassafras – vulnerable to the rapidly spreading laurel wilt disease; photo by F.T. Campbell

In summer 2019 I posted several blogs summarizing my analysis of forest pest issues after 30 years’ engagement. I reported the continuing introductions of tree-killing insects and pathogens; their relentless spread and exacerbated impacts. I noted the continued low priority given these issues in agencies tasked with preventing and solving these problems. Also, Congress provides not only insufficiently protective policies but also way too little funding. I decried the impediments created by several Administrations; anti-regulatory ideology and USDA’s emphasis on “collaborating” with “clients” rather than imposing requirements.

In my blogs, I called for renewed effort to find more effective strategies – as I had earlier advocated in my “Fading Forests” reports (link provided at the end of this blog), previous blogs, and Lovett et al. 2016

Areas of Progress

Now two years have passed. I see five areas of progress – which give me some hope.

1) Important Activities Are Better Funded than I had realized

a) The US Forest Service is putting significant effort into breeding trees resistant to the relevant pests, more than I had realized. Examples include elms and several conifer species in the West – here and here.

b) USDA has provided at least $110 million since FY2009 to fund forest pest research, control, and outreach under the auspices of the Plant Pest and Disease Disaster Prevention Program (§10201 of the Farm Bill). This total does not include additional funding for the spotted lanternfly. Funded projects, inter alia: explored biocontrol agents for Asian longhorned beetle and emerald ash borer; supported research at NORS-DUC on sudden oak death; monitored and managed red palm weevil and coconut rhinoceros beetle; and detected Asian defoliators. Clearly, many of these projects have increased scientific understanding and promoted public compliance and assistance in pest detection and management.

This section of the Farm Bill also provided $3.9 million to counter cactus pests – $2.7 million over 10 years targetting the Cactoblastis moth & here and $1.2 million over four years targetting the Harissia cactus mealybug and here.

flat-padded *Opuntia* cactus – vulnerable to the *Cactoblastis* moth; National Park Service photo

2) Additional publications have documented pests’ impacts – although I remain doubtful that they have increased decision-makers’ willingness to prioritize forest pests. Among these publications are the huge overview of invasive species published last spring (Poland et al.) and the regional overview of pests and invasive plants in the West (Barrett et al.).

3) There have been new efforts to improve prediction of various pests’ probable virulence (see recent blogs and here.

4) Attention is growing to the importance of protecting forest health as a vital tool in combatting climate change — see Fei et al., Quirion et al., and IUCN. We will have to wait to see whether this approach will succeed in raising the priority given to non-native pests by decision-makers and influential stakeholders.

5) Some politicians are responding to forest pest crises – In the US House, Peter Welch (D-VT) is the lead sponsor of H.R. 1389. He has been joined – so far – by eight cosponsors — Rep. Kuster (D-NH), Pappas (D-NH), Stefanik (R-NY), Fitzpatrick (R-PA), Thompson (D-CA), Ross (D-NC), Pingree (D-ME), and Delgado (D-NY). This bill would fund research into, and application of, host resistance! Also, it would make APHIS’ access to emergency funds easier. Furthermore, it calls for a study of ways to raise forest pests’ priority – thus partially responding to the proposal by me and others (Bonello et al. 2020; full reference at end of blog) to create federal Centers for Forest Pest Control and Prevention.

This year the Congress will begin work on the next Farm Bill – might these ideas be incorporated into that legislation?

What Else Must Be Done

My work is guided by three premises:

1) Robust federal leadership is crucial:

The Constitution gives primacy to federal agencies in managing imports and interstate trade.
Only a consistent approach can protect trees (and other plants) from non-native pests that spread across state lines.
Federal agencies have more resources than state agencies individually or in likely collective efforts – even after decades of budget and staffing cuts.

2) Success depends on a continuing, long-term effort founded on institutional and financial commitments commensurate with the scale of the threat. This requires stable funding; guidance by research and expert staff; and engagement by non-governmental players and stakeholders. Unfortunately, as I discuss below, funding has been neither adequate nor stable.

3) Programs’ effectiveness needs to be measured. Measurement must focus on outcomes, not just effort (see National Environmental Coalition on Invasive Species’ vision document).

Preventing New Introductions – Challenges and Solutions

We cannot prevent damaging new introductions without addressing two specific challenges.

1) Wood packaging continues to pose a threat despite past international and national efforts. As documented in my recent blogs, the numbers of shipping containers – presumably with wood packaging – are rising. Since 2010, CBP has detected nearly 33,000 shipments in violation of ISPM#15. The numbers of violations are down in the most recent years. However, a high proportion of pest-infested wood continues to bear the ISPM#15 mark. So, ISPM#15 is not as effective as it needs to be.

We at CISP hope that by mid-2022, a new analysis of the current proportion of wood packaging harboring pests will be available. Plus there are at least two collaborative efforts aimed at increasing industry efforts to find solutions – The Nature Conservancy with the National Wooden Pallet and Container Association; and the Cary Institute with an informal consortium of importers using wooden dunnage.

2) Imports of living plants (“plants for planting”) are less well studied so the situation is difficult to assess. However, we know this is a pathway that has often spread pests into and within the US. There have been significant declines in overall numbers of incoming shipments, but available information doesn’t tell us which types of plants – woody vs. herbaceous, plant vs. tissue culture, etc. – have decreased.

APHIS said, in a report to Congress (reference at end of blog), that introductions have been curbed – but neither that report nor other data shows me that is true.

Scientists are making efforts to improve risk assessments by reducing the number of organisms for which no information is available on their probable impacts (the “unknown unknowns”).

Solving Issues of Prevention

While I have repeatedly proposed radical revisions to the international phytosanitary agreements (WTO SPS & IPPC) that preclude prevention of unknown unknowns (see Fading Forests II and blog), I have also endorsed measures aimed at achieving incremental improvements in preventing introductions, curtailing spread, and promoting recovery of the affected host species.

citrus longhorned beetle exit hole in bonsai tree; USDA APHIS photo

The more radical suggestions focus on: 1) revising the US Plant Protection Act to give higher priority to preventing pests introductions than to facilitating free trade (FF II Chapter 3); 2) APHIS explicitly stating that its goal is to achieve a specific, high level of protection (FF II Chapter 3); 3) APHIS using its authority under the NAPPRA program to prohibit imports of all plants belonging to the 150 genera of “woody” plants that North America shares with Europe or Asia; 4) APHIS prohibiting use of packaging made from solid wood by countries and exporters that have a record of frequent violations of ISPM#15 in the 16 years since its implementation.

Another action leading to stronger programs would be for APHIS to facilitate outside analysis of its programs and policies to ensure the agency is applying the most effective strategies (Lovett et al. 2016). The pending Haack report is an encouraging example.

I have also suggested that APHIS broaden its risk assessments so that they cover wider categories of risk, such as all pests that might be associated with bare-root woody plants from a particular region. Such an approach could speed up analyses of the many pathways of introduction and prompt their regulation.

Also, APHIS could use certain existing programs more aggressively. I have in mind pre-clearance partnerships and Critical Control Point integrated pest management programs. APHIS should also clarify the extent to which these programs are being applied to the shipments most likely to transport pests that threaten our mainland forests, i.e. imports of woody plants belonging to genera from temperate climates. APHIS should promote more sentinel plant programs. Regarding wood packaging, APHIS could follow the lead of CBP by penalizing importers for each shipment containing noncompliant SWPM.

Getting APHIS to prioritize pest prevention over free trade in general, or in current trade agreements, is a heavy lift. At the very least, the agency should ensure that the U.S. prioritize invasive species prevention in negotiations with trading partners and in developing international trade-related agreements. I borrow here from the recent report on Canadian invasive species efforts. (I complained about APHIS’ failure to even raise invasive species issues during negotiation of a recent agricultural trade agreement with China.)

Solving Issues of Spreading Pests

The absence of an effective system to prevent a pest’s spread within the U.S. is the most glaring gap in the so-called federal “safeguarding system”. Yet this gap is rarely discussed by anyone – officials or stakeholders. APHIS quarantines are the best answer – although they are not always as efficacious as needed – witness the spread of EAB and persistence of nursery outbreaks of the SOD pathogen.

APHIS and the states continue to avoid establishing official programs targetting bioinvaders expected to be difficult to control or that don’t affect agricultural interests. Example include laurel wilt, and two boring beetles in southern California – goldspotted oak borer, Kuroshio shot hole borer and polyphagous shot hole borer and their associated fungi.

One step toward limiting pests’ spread would come from strengthening APHIS’ mandate in legislation, as suggested above. A second, complementary action would be for states to adopt quarantines and regulations more aggressively. For this to happen, APHIS would need to revise its policies on the “special needs exemption” [7 U.S.C. 7756]. Then states could adopt more stringent regulations to prevent introduction of APHIS-designated quarantine pests (Fading Forests III Chapt 3).

Finally, APHIS should not drop regulating difficult-to-control species – e.g., EAB. There are repercussions.

APHIS’ dropping EAB has not only reduced efforts to prevent the beetle’s spread to vulnerable parts of the West. It has also left states to come up with a coherent approach to regulating firewood; they are struggling to do so.

Considering interstate movement of pests via the nursery trade, the Systems Approach to Nursery Certification (SANC) program) is voluntary and was never intended to include all nurseries. Twenty-five nurseries were listed on the program’s website as of March 2020. It is not clear how many nurseries are participating now. The program ended its “pilot” phase and “went live” in January 2021. Furthermore, the program has been more than 20 years in development, so it cannot be considered a rapid response to a pressing problem.

Solving Issues of Recovery and Restoration via Resistance Breeding

I endorse the findings of two USFS scientists, Sniezko and Koch citations. They have documented the success of breeding programs when they are supported by expert staff and reliable funding, and have access to appropriate facilities. The principle example of such a facility is the Dorena Genetic Resource Center in Oregon. Regional consortia, e.g., Great Lakes Basin Forest Health Collaborative and Whitebark Pine Ecosystem Foundation are trying to overcome gaps in the system. I applaud the growing engagement of stakeholders, academic experts, and consortia. Questions remain, though, about how to ensure that these programs’ approaches and results are integrated into government programs.

resistant and vulnerable ash seedlings; photo courtesy of Jennifer Koch, USFS

In Bonello et al., I and others call for initiating resistance breeding programs early in an invasion. Often other management approaches, e.g., targetting the damaging pest or manipulating the environment, will not succeed. Therefore the most promising point of intervention is often with by breeding new or better resistance in the host. This proposal differs slightly from my suggestion in the “30 years – solutions” blog, when I suggested that USFS convene a workshop to develop consensus on breeding program’s priorities and structure early after a pest’s introduction.

Funding Shortfalls

I have complained regularly in my publications (Fading Forests reports) and blogs about inadequate funding for APHIS Plant Protection program and USFS Forest Health Protection and Research programs. Clearly the USDA Plant Pest and Disease Management and Disaster Program has supported much useful work. However, its short-term grants cannot substitute for stable, long-term funding. In recent years, APHIS has held back $14 – $15 million each year from this program to respond to plant health emergencies. (See APHIS program reports for FYs 20 and 21.) This decision might be the best solution we are likely to get to resolve APHIS’ need for emergency funds. If we think it is, we might drop §2 of H.R. 1389.

Expanding Engagement of Stakeholders

Americans expect a broad set of actors to protect our forests. However, these groups have not pressed decision-makers to fix the widely acknowledged problems: inadequate resources – especially for long-term solutions — and weak and tardy phytosanitary measures. Employees of federal and state agencies understand these issues but are restricted from outright advocacy. Where are the professional and scientific associations, representatives of the wood products industry, forest landowners, environmental NGOs and their funders, plus urban tree advocates – who could each play an important role? The Entomological Society’s new “Challenge” is a welcome development and one that others could copy.

SOURCES

Bonello, P., Campbell, F.T., Cipollini, D., Conrad, A.O., Farinas, C., Gandhi, K.J.K., Hain, F.P., Parry, D., Showalter, D.N, Villari, C. and Wallin, K.F. (2020) Invasive Tree Pests Devastate Ecosystems—A Proposed New Response Framework. Front. For. Glob. Change 3:2. doi: 10.3389/ffgc.2020.00002

Krishnankutty, S., H. Nadel, A.M. Taylor, M.C. Wiemann, Y. Wu, S.W. Lingafelter, S.W. Myers, and A.M. Ray. 2020. Identification of Tree Genera Used in the Construction of Solid Wood-Packaging Materials That Arrived at U.S. Ports Infested With Live Wood-Boring Insects. Journal of Economic Entomology 2020, 1 – 12

Liebhold, A.M., E.G. Brockerhoff, L.J. Garrett, J.L. Parke, and K.O. Britton. 2012. Live plant imports: the major pathway for forest insect and pathogen invasions of the US. Front. Ecol. Environ. 2012; 10(3):135-143

Lovett, G.M., M. Weiss, A.M. Liebhold, T.P. Holmes, B. Leung, K.F. Lambert, D.A. Orwig, F.T. Campbell, J. Rosenthal, D.G. McCullough, R. Wildova, M.P. Ayres, C.D. Canham, D.R. Foster, SL. Ladeau, and T. Weldy. 2016. NIS forest insects and pathogens in the US: Impacts and policy options. Ecological Applications, 26(5), 2016, pp. 1437–1455

Mech, A.M., K.A. Thomas, T.D. Marsico, D.A. Herms, C.R. Allen, M.P. Ayres, K.J. K. Gandhi, J. Gurevitch, N.P. Havill, R.A. Hufbauer, A.M. Liebhold, K.F. Raffa, A.N. Schulz, D.R. Uden, & P.C. Tobin. 2019. Evolutionary history predicts high-impact invasions by herbivorous insects. Ecol Evol. 2019 Nov; 9(21): 12216–12230.

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

Roy, B.A., H.M Alexander, J. Davidson, F.T Campbell, J.J Burdon, R. Sniezko, and C. Brasier. 2014. Increasing forest loss worldwide from invasive pests requires new trade regulations. Front Ecol Environ 2014; 12(8): 457–465

Schulz, A.N., A.M. Mech, M.P. Ayres, K. J. K. Gandhi, N.P. Havill, D.A. Herms, A.M. Hoover, R.A. Hufbauer, A.M. Liebhold, T.D. Marsico, K.F. Raffa, P.C. Tobin, D.R. Uden, K.A. Thomas. 2021. Predicting non-native insect impact: focusing on the trees to see the forest. Biological Invasions.

United States Department of Agriculture Animal and Plant Health Inspection Service. Report on the Arrival in the US of Forest Pests Through Restrictions on the Importation of Certain Plants for Planting. https://www.caryinstitute.org/sites/default/files/public/downloads/usda_forest_pest_report_2021.pdf

Posted by Faith Campbell

New Study on Forest Carbon and Pests: The Picture is Ugly

lodgepole pines killed by mountain pine beetle in British Columbia; photo courtesy of Wikipedia

Natural systems, especially forests, could provide as much as 37% of the near-term mitigation necessary to meet Paris global climate goals. In the US, conservation, restoration, and improved land management could provide carbon sequestration equivalent to an estimated 21% of current net annual emissions.

However, the current U.S. forest carbon sink, which includes soils and standing and downed wood as well as live trees, might be in jeopardy due to increasing levels of disturbance, conversion, and/or declining sequestration rates in old growth stands.

Insects and plant diseases are one such disturbance agent. Acting alone or in combination with other forest stressors, they can damage or kill large numbers of trees in short periods of time, thereby reducing carbon sequestration and increasing emissions of stored carbon through decomposition of wood in dead or injured trees.

Historically, native and introduced insects and diseases have impacted an estimated 15% of the total U.S. forest cover annually. This impact is likely to increase. One study (Fei et al., 2019) found that an estimated 41% of the live forest biomass in the contiguous U.S. could be impacted by the 15 most damaging introduced pests already established in the U.S. Continuing introductions of new pests and exacerbated effects of native pests associated with climate change portend worsening losses of live trees. These rising impact of pests, combined with more frequent and severe fires and other forest disturbances, are likely to negate efforts to improve forests’ carbon sequestration capacity.

Sources of information about introduced pests’ impacts is available from, inter alia Campbell and Schlarbaum Fading Forests II and III, Lovett et al 2016, Poland et al. 2021, many blogs on this site, and pests’ profiles posed here under “invasive species” tab. Chapter 4 of Poland et al. (2021) provides a summary of what is known about interactions between invasive species and climate change – both climate impacts on bioinvaders and bioinvaders’ effect on carbon sequestration.

The United States and other major polluting countries have certain advantages. Their strong economies have the scientific and financial resources needed to implement effective invasive species prevention and forest management strategies. At the same time, many of them receive the most new forest pests – because they are major importers. These introduced pests pose the most serious and urgent near-term ecological threat to their forests and all the ecosystem services forests provide.

So, reducing insect and disease impacts to forests can simultaneously serve several goals—carbon sequestration, biodiversity conservation, and protecting the myriad economic and societal benefits of forests. See the recent IUCN report on threatened tree species.

A Major New Study

A new study by Quirion et al. (2021) takes another step in quantifying the threat to U.S. forests’ ability to sequester carbon by analyzing data from National Forest Inventory plots. Unfortunately, the re-measurement data for the period 2001 – 2019 are not available in the NFI for the Rocky Mountain states, which represents a critical data gap in the NFI program. This gap might not have had a significant impact on the national findings, however, because while the insect damage level (measured by an earlier inventory round) was quite severe in the Rocky Mountain States, the relatively slow growth of trees in that region means carbon sequestration rates are low.

Forest stand productivity – and carbon sequestration — will typically decline immediately after pest outbreaks, then recover or even increase beyond pre-outbreak levels depending on the productivity and maximum achieved biomass of replacement plant species and related soil characteristics. However, when prevalence of the disturbance increases, by, for example, more frequent pest outbreaks, carbon stocks in standing trees and sequestration rates can be reduced for extended periods.

Findings

Nationally, insects and diseases have decreased carbon sequestration by live trees on forest land by 12.83 teragrams carbon per year. This equals ~ 9% of the contiguous states’ total annual forest carbon sequestration and equivalent to the CO₂ emissions from over 10 million passenger vehicles driven for one year.
This estimate includes the impacts of both native and introduced insects and diseases, because the NFI database does not distinguish between them.
Insect-caused mortality had a larger impact than disease-caused mortality (see below). Forest plots recently impacted by insect disturbance sequestered on average 69% less carbon in live trees than plots with no recent disturbance. Plots recently impacted by disease disturbance sequestered on average 28% less carbon in live trees than plots with no recent disturbance.
Ecoprovinces in which the greatest annual reductions in live tree carbon sequestration due to pests were the Southern Rocky Mountain Steppe, Cascade Mixed Forest, Midwest Broadleaf Forest, and Laurentian Mixed Forest. (Ecoprovinces are outlined – but not named – in Quirion et al. 2021; more complete information is provided in the supplementary material.)

If this study had been carried out in the 1920’s, when chestnut blight and white pine blister rust were spreading across vast areas and killing large trees, the impact of diseases would have been much higher. Today, the most widespread impacts of diseases are on either small trees (e.g., redbay succumbing to laurel wilt) or slow-growing, high-elevation trees (e.g., whitebark and limber pine to white pine blister rust). As long as no equivalents of those earlier diseases are introduced, insects will probably continue to have the larger impacts.

western white pine killed by blister rust; photo from National Archives

Quirion et al. 2021 note that their estimates should be considered conservative. The USFS’s inventory records only major disturbances. That is, when mortality or damage is equal to or exceeds 25% of trees or 50% of an individual tree species’ count on an area of at least 0.4 ha. This criterion largely excludes less severe pest disturbances, including those from which trees recover but which might have temporary negative effects on carbon sequestration.

The study’s authors note that their work has important limitations. The dearth of data from the Rocky Mountain states is one. Other factors not considered include transfers of carbon from live biomass to dead organic matter, soils, and salvaged or preemptively harvested wood products. As trees die from pests or diseases, their carbon becomes dead wood and decays slowly, producing a lag in the carbon emissions to the atmosphere. A small fraction of the carbon in dead wood might be incorporated into soil organic matter, further delaying the emissions. A full accounting of the carbon consequences of pests and diseases would require assessment of these lags, probably through a modeling study.

affects of mountan pine beetle on lodgepole pine in Rocky Mountain National Park, Colorado photo from Wikimedia

Actions to Maintain Carbon Sequestration

Quirion et al. (2021) outline several actions that would help protect the ability of America’s forests to sequester carbon. These suggestions address both native and introduced pests, since both contribute to the threatened reduction in capacity.

Concerning native pests, the authors call for improved forest management, but warn that measures must be tailored to species and environmental context.

Concerning introduced insects and pathogens, Quirion et al. (2021) call for strengthening international trade policies and phytosanitary standards, as well as their enforcement. The focus should be on the principal pathways: wood packaging (click on “wood packaging” category for on this blog site) and imported plants (click on “plants as vectors” category for on this blog site). Specific steps to reduce the rate of introduction of wood-boring insects include enforcement to increase compliance with the international treatment standard (ISPM#15), requiring trade partners – especially those which have repeatedly shipped infested packaging – to switch to packaging made from alternative materials. Introductions via the plant trade could be reduced by requiring foreign shippers to employ integrated management and critical control point systems (per criteria set by the U.S.) and using emergency powers (e.g., NAPPRA) to further restrict imports of the plants associated with the highest pest risk, especially plant species that are congeneric with native woody plants in North America. See Lovett et al 2016; Fading Forests II & III

As backup, since even the most stringent prevention and enforcement will not eliminate all risk, the authors urge increased funding for and research into improved inspection, early detection of new outbreaks, and strategic rapid response to newly detected incursions.

To reduce impacts of pests established on the continent – both recently and years ago – they recommend increasing and stabilizing dedicated funding for classical biocontrol, research into technologies such as sterile-insect release and gene drive, and host resistance breeding.

Thinning is useful in reducing damage by native bark beetles to conifers. However, it has not been successful in controlling introduced pests for which trees do not have an evolved resistance. Indeed, preemptive harvesting of susceptible species can harm forest ecosystems directly through impacts of the harvesting operation and indirectly as individual trees that may exhibit resistance are removed, reducing the species’ ability to develop resistance over time.

Further research is needed to clarify several more issues, including whether introduced pests’ impacts are additive to, or interact with, those of native species and/or other forest stressors.

SOURCE

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

SOURCES of additional information

Campbell, F.T. and S.E. Schlarbaum. Fading Forest reports at http://treeimprovement.utk.edu/FadingForests.htm

Lovett, G.M., M. Weiss, A.M. Liebhold, T.P. Holmes, B. Leung, K.F. Lambert, D.A. Orwig, F.T. Campbell, J. Rosenthal, D.G. McCullough, R. Wildova, M.P. Ayres, C.D. Canham, D.R. Foster, S.L. Ladeau, and T. Weldy. 2016. Nonnative forest insects and pathogens in the United States: Impacts and policy options. Ecological Applications, 26(5), 2016, pp. 1437-1455

Poland, T.M., Patel-Weynand, T., Finch, D., Miniat, C. F., and Lopez, V. (Eds) (2019), Invasive Species in Forests and Grasslands of the United States: A Comprehensive Science Synthesis for the United States Forest Sector. Springer Verlag. Available for download at no cost at https://www.fs.usda.gov/treesearch/pubs/61982

Posted by Faith Campbell

Tuning in to the News – Mostly Depressing

In late July I participated in the annual meeting of the National Plant Board (NPB) – the organization representing the states’ phytosanitary agencies. USDA’s APHIS, DHS’ Bureau of Customs and Border Protection (CBP), and various industry associations also participated in the meeting. As usual, I learned lots of depressing developments.

A. Old problems continue to vex:

rhododendron plant infested by P. ramorum; photo by Jennifer Parke, Oregon State University

1) Sudden Oak Death in the Nursery Trade – Again!!!

As you might remember, spring 2019 saw an alarming number of plants infested by the sudden oak death pathogen (Phytophthora ramorum) shipped from west coast nurseries to nurseries in 18 states. Another major incident occurred in 2021. The California Oak Mortality Task Force (COMTF) newsletter for June 2021 reports that one nursery in Oregon shipped plants exposed to P. ramorum to big-box stores in 36 states — twice the number of states that received pathogen-exposed plants in 2019.

The first such incident was in 2004 – 17 years ago! Officials of the states that receive these infested plants are angry that every few years they must divert their resources from other duties to inspect nurseries in their states that have been exposed to the pathogen. They note that these “trace-forward” projects cost state governments money and prevent their carrying out other duties; they also impose significant costs on the in-state nurseries due to holds on sales. When infested plants are found, all these costs rise substantially.

The plant health official from Alabama noted that a single west coast nursery that had repeatedly been found to have infected plants shipped 29 lots of host plants to her state in spring 2021. As is clear from the COMTF article, other states also received thousands of plants that had been exposed to the pathogen. The Alabama official questioned why APHIS tilts so far toward a regulatory system that makes it possible for the “exporting” nurseries to ship. The result – too often – is that an infection at one small business can (repeatedly) impose high costs on hundreds of receiving nurseries and states. [I wonder whether anyone has considered a lawsuit against the source nurseries claiming damages? Would that be successful if the regulatory agencies approved the shipments because – at that time – their inspections had failed to detect the problem?]

Officials from the three west coast states, however, want to support their own nurseries’ efforts to relax regulations and maintain or open markets in the central and eastern states. They point to their own considerable efforts to inspect and certify the pest-free status of nurseries in their states.

Because of the different points of view among the states, the National Plant Board per se has never taken a position on the issue.

However, many states – and even APHIS Deputy Administrator El-Lissy – agree that something is not working. So APHIS is in the midst of reviewing its program, with input from NPB members. Such program reviews have been undertaken several times over the past 18 years. So far, they have never produced a program that effectively stops sales of pathogen-infested plants.

2) Contaminated Wood Packaging

Kevin Harriger of CBP reported that over the nine-month period October 2020 – June 2021, CBP intercepted 1,563 shipments that were in violation of ISPM#15, the international rule that requires that wood packaging be treated to kill pests. Most, or 1,148 shipments (73%), lacked the required mark certifying treatment. Four hundred fifteen (26%) of the total number of shipments had a live pest present. Nearly three quarters of the non-compliant shipments transported miscellaneous cargo. This is not a surprise: all of these characteristics are in keeping with past experience.

Meanwhile, APHIS Deputy Director El-Lissy said APHIS was working with importers, exporting countries’ departments of agriculture, and others to improve compliance. Apparently there were two high-profile incidents when shipments of car components were rejected because of ISPM#15 issues. I am trying to learn more about these incidents.

I recently blogged about the pest risk associated with incoming shipping containers and dunnage.

3) Asian ~~Gypsy~~ Moths (Tussock moths) Still Infesting Ships

Harriger also said that the period 2019-2020 saw the largest number of ships infested by Asian tussock moth eggs since the program began in 2012. [I am aware that the Entomological Society is searching for a new name for this group of insects.] On average, 12 of 100 approaching vessels was infested. CBP is using sophisticated models to identify regions within Asian ports where conditions exacerbate the risk of moth contamination. CBP can match individual ships’ loading records to this information to pinpoint which are most likely to be infested.

Oregon and Washington continue to find both Asian and European tussock moths in traps along the Columbia River. Such detections prompt eradication programs of varying expense and disruption.

[In April, I blogged about a report evaluating the risk posed by several Asian tussock moths; the report was prepared by experts under the auspices of the North American Plant Protection Organization.]

B. In addition to the arrival of new pests, there is an alarming spread of established ones:

1) Beech leaf disease

State phytosanitary officials reported detections of beech leaf disease (BLD) in Maine and Virginia. The devastating impact of BLD on this hard mast tree species is described here. BLD has now spread through much of southern New England (Connecticut, Rhode Island, Massachusetts) and up the coast to Maine. Connecticut reports that trees of all sizes are affected. Maine reports that the disease is widespread in the central coastal region.

beech trees in Prince William Forest Park

Virginia reported that the disease has been detected in Prince William Forest Park, a forested area south of Washington, D.C., managed by the National Park Service. This detection is too recent to say how widespread it is.

2) Laurel wilt

Kentucky’s plant health officer reported that laurel wilt disease has been detected on sassafras trees in Louisville, at the northern tip of the state and across the river from Ohio. He noted that a second host plant, spice bush, is in the nursery trade. While laurel wilt is not regulated, officials are concerned about its impact in natural forests. Neighboring states are concerned.

sassafras in northern Virginia; photo by F.T. Campbell

I learned by looking at the map that laurel wilt has also been detected in Sullivan County, Tennessee, on the Virginia border.

3) Spotted Lanternfly

This pest of grapes, tree fruits, and a wide variety of native trees is spreading in Pennsylvania, Delaware, New Jersey, and Maryland. It has also been found in Ithaca, NY, and in Connecticut. The populations in Virginia and West Virginia also continue to spread; a disjunct outbreak has been detected in Prince William County, VA. (south of D.C.). Most alarming are disjunct populations in Ohio on the West Virginia border and in Indiana on the Ohio River border with northern Kentucky. See map here.

The Indiana population has been present for several years. The affected woodland is close to RV parks and other facilities that make further spread likely.

California has established an external quarantine targetting the spotted lanternfly .

C. Wrestling with Continuing Issues:

1) States try to compensate for APHIS’ end of regulating the emerald ash borer and firewood

The members of the NPB have spent years discussing the pros and cons of continuing to regulate ash wood to contain the emerald ash borer (EAB). As I blogged earlier, APHIS has ended its regulatory program. One state – Minnesota – is seeking to use an APHIS procedure to get APHIS’ continued protection from importation of EAB-infested wood (presumably from Canada). Under the Federally Recognized State Managed Phytosanitary Program (FRSMP), a state petitions APHIS to recognize its program for a specific pest. If APHIS grants that recognition, the agency will support the state by continuing to regulate imports of that pest or commodities that might transport the pest when they are destined for the regulating state.

The states have also tried to formulate a system to maintain regulation of firewood (nearly all states’ firewood regulations were based on the federal regulation of all hardwoods to prevent transport of the EAB). As part of this process, the NPB developed guidelines for adoption of regulations by the individual states (available here). The NPB members are just beginning to explore whether states might set up third-party certification system(s). Among the challenges to any harmonization are states’ differing legal authorities and disagreement on what threat levels should be applied, and for how long.

2) New information about the Asian longhorned beetle in South Carolina

ALB in South Carolina; photo by R. Brad Thompson, APHIS

South Carolina authorities reported that dendrological studies indicated Asian longhorned beetle (ALB) had been present near Charleston, S.C. since 2012, and possibly earlier. The population has the same genetic makeup as the outbreak in Ohio. This might be explained by either transport of infested wood from Clermont County, Ohio, or that wood packaging entering Charleston harbor came from the same part of China. (Charleston is an important port.) In South Carolina, ALB attacks primarily red maple – as is true at the other infestation sites. However, maple densities are much lower in the swamps of South Carolina and scientists don’t know whether the ALB will fly farther or intensify attacks on other host species. Other questions raised by differences between South Carolina and other, more northern, outbreak sites include possible changes in the beetle’s life cycle and flight periods.

Authorities noted the extremely difficult conditions, which impede survey and control efforts – which I described in an earlier blog.

One innovation was sharing of resources: staff from the North Carolina and Tennessee departments of agriculture went to South Carolina to help with surveys. The Resource Sharing Initiative was started a few years ago as a collaborative effort of APHIS and the NPB. This was the first time states tried it. There were several issues that had to be worked out. One issue was the long time it takes to train people to recognize ALB symptoms. All three states’ officials said the project was worthwhile.

black walnut in Fairfax County, VA — in an area where thousand cankers disease has been present for more than a decade; photo by FT Campbell

3) Recinding quarantines of thousand cankers disease of walnut

States which adopted quarantines targetting this insect/pathogen complex a decade ago now think that it poses little risk to black walnut (Juglans nigra) growing in its native range (as distinct from trees planted in the West). Several are in the process of rescinding their quarantines. I think these states have considered the science carefully and are taking the appropriate action.

4) Nursery self-certification – System Set Up; Will Nurseries Participate? Will Customers Support the Process?

Craig Regelbrugge of AmericanHort noted that the SANC program has now been officially launched – it has graduated from being a pilot program. [SANC stands for Systems Approach to Nursery Certification] Participants are exploring incentives to recruit wider participation by nurseries that produce plants and how to get support from plant retailers. SANC is conceived as an elite program for the best nurseries and marketplace leaders. It was never intended to be a remedial program to clean up problem issues such as the P. ramorum debacle. To work, it seems to me, SANC will need to find a way to persuade customers to want to pay more for quality plants. Hence the critical importance of getting retailers involved.

Posted by Faith Campbell

On the Rise: US Imports & the Risks of Tree-killing Pests

containers at Port of Long Beach; photo courtesy of Bob Kanter, Port of Long Beach

Here I update information on two of the major pathways by which tree-killing pests enter the United States: wood packaging and living plants (plant for planting).

Wood Packaging

Looking at wood packaging material, we find rising volumes for both shipping containers – and their accompanying crates and pallets; and dunnage.

Crates and pallets – Angell (2021; full citation at the end of the blog) provides data on North American maritime imports in 2020. The total number of TEUs [a standardized measure for containerized shipment; defined as the equivalent of a 20-foot long container] entering North America was 30,778,446.U.S. ports received 79.6% of these incoming containers, or 24,510,990 TEUs. Four Canadian ports handled 11.4% of the total volume (3,517,464 TEUs; four Mexican ports 8.9% (2,749, 992 TEU). Angell provides data for each of the top 25 ports, including those in Canada and Mexico.

To evaluate the pest risk associated with the containerized cargo, I rely on a pair of two decade-old studies. Haack et al. (2014) determined that approximately 0.1% (one out of a thousand) shipments with wood packaging probably harbor a tree-killing pest. Meissner et al. (2009) found that about 75% of maritime shipments contain wood packaging. Applying these calculations, we estimate that 21,000 of the containers arriving at U.S. and Canadian ports in 2020 might have harbored tree-killing pests.

While the opportunity for pests to arrive is obviously greatest at the ports receiving the highest volumes of containers with wood packaging, the ranking (below) does not tell the full story. The type of import is significant. For example, while Houston ranks sixth for containerized imports, it ranks first for imports of break-bulk (non-containerized) cargo that is often braced by wooden dunnage (see below). Consequently, Houston poses a higher risk than its ranking by containerized shipment might indicate.

Also, Halifax Nova Scotia ranks 22^nd for the number of incoming containerized shipments (258,185 containers arriving). However, three tree-killing pests are known to have been introduced there: beech bark disease (in the 1890s), brown spruce longhorned beetle (in the 1990s), and European leaf-mining weevil (before 2012) [Sweeney, Annapolis 2018]

The top ten ports receiving containerized cargo in 2020 were

Port 2020 market share 2020 TEU volume

Los Angeles 15.6% 4,652,549

Long Beach 13% 3,986,991

New York/New Jersey 12.8% 3,925,469

Savannah 7.5% 2,294,392

Vancouver BC 5.8% 1,797,582

Houston 4.2% 1,288,128

Manzanillo, MX 4.1% 1,275,409

Seattle/Tacoma 4.1% 1,266,839

Virginia ports 4.1% 1,246,609

Charleston 3.3% 1,024,059

Import volumes continue to increase since these imports were recorded. U.S. imports rose substantially in the first half of 2021, especially from Asia. Imports from that content reached 9,523,959 TEUs, up 24.5% from the 7,649,095 TEUs imported in the first half of 2019. The number of containers imported in June was the highest number ever (Mongelluzzo July 12, 2021).

Applying the calculations from Haack et al. (2014) and Meissner et al. (2009) to the 2021 import data, we find that approximately 7,100 containers from Asia probably harbored tree-killing pests in the first six months of the year. (The article unfortunately reports data only for Asia.) Industry representatives quoted by Mongelluzzo expect high import volumes to continue through the summer. This figure also does not consider shipments from other source regions.

Dunnage on the pier at Port of Houston; photo by Port of Houston

Infested dunnage – Looking at dunnage, imports of break-bulk (non-containerized) cargo to Houston – the U.S. port which receives the most – are also on the upswing. Imports in April were up 21% above the pandemic-repressed 2020 levels.

Importers at the port complain that too often the wooden dunnage is infested by pests, despite having been stamped as in compliance with ISPM#15. CBP spokesman John Sagle confirms that CBP inspectors at Houston and other ports are finding higher numbers of infested shipments. CBP does not release those data, so we cannot provide exact numbers (Nodar, July 19, 2021).

The Houston importers’ suspicion has been confirmed by data previously provided by CBP to the Continental Dialogue on Non-Native Insects and Diseases. From Fiscal Year 2010 through Fiscal Year 2015, on average 97% of the wood packaging (all types) found to be infested bore the stamp. CBP no longer provides data that touch on this issue.

Detection of pests in the dunnage leads to severe problems. Importers can face fines up to the full value of the associated cargo. Often, the cargo is re-exported, causing disruption of supply chains and additional financial losses (Nodar, July 19, 2021).

In 2019 importers and shippers from the Houston area formed an informal coalition with the Cary Institute of Ecosystem Studies to try to find a solution to this problem. The chosen approach is for company employees to be trained in CBP’s inspection techniques, then apply those methods at the source of shipments to identify – and reject – suspect dunnage before the shipment is loaded. In addition, the coalition hopes that international inspection companies, which already inspect cargo for other reasons at the loading port will also be trained to inspect for pests. Steps to set up such a training program were interrupted by the COVID-19 pandemic, but are expected to resume soon (Nodar, July 19, 2021).

Meanwhile, the persistence of pests in “treated” wood demands answers to the question of “why”. Is the cause fraud – deliberate misrepresentations that the wood has been treated when it has not? Or is the cause a failure of the treatments – either because they were applied incorrectly or they are inadequate per se?

ISPM#15 is not working adequately. I have said so. Gary Lovett of the Cary Institute has said so (Nodar July 19, 2021). Neither importers nor regulators can rely on the mark to separate pest-free wood packaging from packaging that is infested.

APHIS is the agency responsible for determining U.S. phytosanitary policies. APHIS has so far not accepted its responsibility for determining the cause of this continuing issue and acting to resolve it. Preferably, such detection efforts should be carried out in cooperation with other countries and such international entities as the International Plant Protection Convention (IPPC) and International Union of Forest Research Organizations (IUFRO). However, APHIS should undertake such studies alone, if necessary.

In the meantime, APHIS and CBP should assist importers who are trying to comply by facilitating access to information about which suppliers often supply wood packaging infested by pests. The marks on the wood packaging includes a code identifying the facility that carried out the treatment, so this information is readily available to U.S. authorities.

Plants for Planting

A second major pathway of pest introduction is imports of plants for planting. Data on this pathway are too poor to assess the risk – although a decade ago it was found that the percentage of incoming shipments of plants infested by a pest was 12% – more than ten times higher than the proportion for wood packaging (Liebhold et al. 2012).

According to APHIS’ annual report, in 2020 APHIS and its foreign collaborators inspected 1.05 billion plants in the 23 countries where APHIS has a pre-clearance program. In other words, these plants were inspected before they were shipped to the U.S. At U.S. borders, APHIS inspected and cleared another 1.8 billion “plant units” (cuttings, rooted plants, tissue culture, etc.) and nearly 723,000 kilograms of seeds. Obviously, the various plant types carry very different risks of pest introduction, so lumping them together obscures the pathway’s risk. The report does not indicate whether the total volume of plant imports rose or fell in 2020 compared to earlier years.

SOURCES

Angell, M. 2021. JOC Rankings: Largest North American ports gained marke share in 2020. June 18, 2021. https://www.joc.com/port-news/us-ports/joc-rankings-largest-north-american-ports-gained-market-share-2020_20210618.html?utm_campaign=CL_JOC%20Port%206%2F23%2F21%20%20_PC00000_e-production_E-103506_TF_0623_0900&utm_medium=email&utm_source=Eloqua

Haack R.A., Britton K.O., Brockerhoff, E.G., Cavey, J.F., Garrett, L.J., et al. (2014) Effectiveness of the International Phytosanitary Standard ISPM No. 15 on Reducing Wood Borer Infestation Rates in Wood Packaging Material Entering the United States. PLoS ONE 9(5): e96611. doi:10.1371/journal.pone.0096611

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

Meissner, H., A. Lemay, C. Bertone, K. Schwartzburg, L. Ferguson, L. Newton. 2009. Evaluation of Pathways for Exotic Plant Pest Movement into and within the Greater Caribbean Region. A slightly different version of this report is posted at 45^th Annual Meeting of the Caribbean Food Crops Society https://econpapers.repec.org/paper/agscfcs09/256354.htm

Mogelluzzo, B. July 12, 2021. Strong US imports from Asia in June point to a larger summer surge.

Nodar, J. July 19, 2021. https:www.joc.com/breakbulk/project-cargo/breakbult-volume-recovery-triggers-cbp-invasive-pest-violations_20210719.htm

Posted by Faith Campbell

International Phytosanitary System Impedes Prevention

*Eugenia koolauensis* (endangered) damaged by ohia rust; photo courtesy of the U.S. Army Natural Resources Program, Oahu

I have written often about failings of the international phytosanitary systems – starting with my report Fading Forests II in 2004, and continuing in many blogs. As the International Year of Plant Health comes to an end, I do so again. I begin with a key recommendation.

Australia’s experience dealing with myrtle rust (Austropuccina psidii) demonstrates the need to integrate agencies responsible for conservation of natural ecosystems into the determination and implementation of phytosanitary policy.

These environmental agencies should be active participants in setting up surveillance and diagnostics protocols and on-the-ground surveillance, and should be directly involved in emergency response. Federal agricultural agencies have technical expertise in biosecurity but lack expertise in key elements of environmental management. In the Australian context, this recommendation is made by several studies cited by Carnegie and Pegg (2018) – full citation at the end of this blog. I strongly endorse the recommendation for the United States. In the U.S., the appropriate agencies would include USDA’s Forest Service and the Department of Interior’s Fish and Wildlife Service.

While the USDA Forest Service is (apparently) more involved in US phytosanitary efforts than its Australian counterpart, its voice in setting USDA phytosanitary policy is limited to the most narrow details, e.g., treatment protocols for wood packaging.

Carnegie and Pegg note a second common problem: the ongoing decline in forest entomology and pathology capacity in government agencies. This decline has long been decried by U.S. natural resource experts as depriving agencies of needed expertise – but we have not yet managed to raise agency budgets so as to reverse it.

The forests of Australia, New Zealand, nearby islands, and South Africa formed during the period of the supercontinent Gondwana – 300 million years ago. While the threat to these unique forests from non-native pests is severe, so far it arises from a limited number of organisms. These are Phytophthora cinnamomi, Austropuccinia psidii, polyphagous shot hole borer and Fusarium fungus (in South Africa), and – in the future, laurel wilt disease. All these organisms threaten multiple hosts. In contrast, the threat to America’s forests comes from more than 100 highly damaging non-native insects, pathogens, and nematodes already here. Some threaten multiple hosts. Plus there is the constant risk of new introductions. Surely our federal conservation agencies have important resources to defend and expertise to contribute to the effort.

Flaws in the System

The international phytosanitary rules adopted by both the World Trade Organization’s Agreement on the Application of Sanitary and Phytosanitary Measures [WTO SPS Agreement] and the International Plant Protection Convention [IPPC] are fundamentally flawed. That is, they require regulatory officials to be unrealistically certain about an organism’s “pest” potential before regulating it. Yet uncertainty is likely to be at its highest at two critical times: before invasion or at its earliest stage. These times are precisely when phytosanitary actions are likely to be most effective.

The effect of this demand for certainty is exacerbated by decision-makers’ caution when confronted with the potential that their action might harm an economic interest. The vast majority won’t impose a regulation until they are sure that the organism under consideration poses a major threat to plant health.

Yet at the same time, most phytosanitary officials rarely carry out the scientific studies that might answer such questions about the risk.

For example, USDA APHIS has created its own Catch 22. It has not funded laboratory tests to get preliminary information on how vulnerable North American tree genera are to the 38 new Phytophthora species detected in Southeast Asia [see earlier blog]. European scientists are doing this testing; it is unclear whether their work is supported by European governments. American scientists could build on the Europeans’ work since our continents share many plant genera – but since vulnerability might vary at the species level, we still must assess North American species separately. At the same time as APHIS is not sponsoring such tests, it refuses to propose acting under its NAPPRA authority link to temporarily prohibit imports of Asian hosts of the Phytophthoras because it lacks information demonstrating the risk they pose to North American plants!

Sometimes, other agencies step in to fill the gap. Thus, the USDA Forest Service funded research to demonstrate that strains of the ‘ōhi‘a rust pathogen not yet introduced to the U.S. posed a risk to native plants in Hawai`i. (See the linked description and additional information later in this blog.) The Forest Service has also funded “sentinel gardens” – plantings inside the U.S. and abroad that are closely monitored to detect new pests.

British forest pathologist Clive Brasier (white hair) searching for *Phytophthora* species in Vietnam

Three pathogens illustrate the problems clearly:

1) brown alga in the Phytophthora genus;

2) myrtle (or ohia or eucalyptus) rust Austropuccinia psidii; and

3) the ophiostomatoid laurel wilt fungus Raffaelea lauricola.

These organisms present a variety of challenges to various countries. Individually and together, these pathogens threaten to transforms forest floras around the world.

Spread: the first two are spread internationally by movement of plants for planting but also spread locally by rain or wind. The third, laurel wilt fungus, arrived in the U.S. when its insect vector, the redbay ambrosia beetle Xyleborus glabratus, hitched a ride in solid wood packaging material.

How countries prepared for pathogen invasion – not always successfully

Numerous plant pathogens in the Phytophthora genus have long had the attention of phytosanitary officials. However, the species that causes sudden oak death (P. ramorum) was unknown when it was introduced to North America and Europe in the late 1980s or early 1990s. The established phytosanitary measures on two continents failed to detect and prevent its introduction.

areas of Australia vulnerable to myrtle rust; Australian Department of Agriculture and Water Resources

The myrtle rust pathogen was already recognized by phytosanitary officials in Australia, New Zealand, and New Caledonia as a severe potential threat, especially to Eucalyptus in both natural forests and plantations. Its appearance in Hawai`i in 2005 raised the level of concern. However, that awareness neither prevented its entry to Australia (probably, although not certainly, on imported plants or foliage) nor prompted its detection early enough for eradication. New Zealand and New Caledonia became infested by wind transport of the pathogen from Australia. [For a thorough discussion of the Australia’s extensive preparations for possible introduction of this pathogen, see Carnegie and Pegg 2018, full citation at the end of this blog.]

The laurel wilt fungus was unknown before it was detected in Georgia, U.S.A. Phytosanitary officials were certainly aware of the pest risk associated with wood packaging material (see Fading Forests II, chapter 3) but at the time the invasion was detected – 2003 – U.S. regulations required that the wood be debarked only, not treated to kill pests.

redbay tree killed by laurel wilt in Georgia

Pathogens are more difficult to detect and manage than insects. They also get less attention. I can think of three possible reasons: 1) Usually we can’t see a pathogen – we literally can’t put a face on the “enemy”. 2) Disease intensity can vary depending on ecological factors, so it is more difficult to understand than an insect feeding on a plant. 3) In recent decades, many invading insects have been linked to a singlepathway of introduction — wood packaging — while pathogens enter through association with a myriad of imports, especially a variety of imported plants. A single pathway is a concept that is easier to understand and address. Because pathogens get little attention, it is more difficult to obtain data quantifying their risks.

The rapid spread and high mortality of laurel wilt in one host – redbay trees (Persea borbonia) – and threat to a second—sassafras (Sassafras albidum) – have alerted scientists to this threat. The pathogen apparently threatens trees and shrubs in the Lauraceae family that are native to regions other than Southeast Asia. These areas include the tropical Americas, Australia, Madagascar, and islands in the eastern Atlantic (Azores, Canary Islands, and Madeira). I understand that Australian phytosanitary officials are aware of this risk, but I don’t know about officials in the other regions. For example, laurel wilt is not listed among the pathogens thought to pose the greatest risk in Europe, i.e., the A1 list of the European and Mediterranean Plant Protection Organization (EPPO)

Why do some organisms suddenly disperse widely? Who is figuring out why?

The myrtle rust pathogen Austropuccinia psidii experienced a burst of introductions after 2000: it was 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. It is believed to have been carried to Hawai`i on cut vegetation for the floral trade; to New Caledonia and New Zealand by wind from Australia across the Tasman Sea. The introduction pathway to Australia has never been determined, although it first was detected in a nursery. I don’t have information on how it was introduced to Japan or China. Has anyone tried to figure out what triggered this expansion? Was it some fad in horticulture or floriculture? Would it not be useful to learn what happened so we can try to prevent a repetition?

Similar sudden dispersals occurred during roughly the same period for Phytophthora ramorum and the erythrina gall wasp (Quadrastichus erythrinae). The latter spread across the Indian and Pacific oceans within a dozen years of its discovery. Again, was there some fad that prompted international trade in host material? Or did the insect suddenly start utilizing transport facilities such as aircraft interiors or holds? Has anyone tried to figure this out? I doubt anyone is even searching for and recording the presence of the gall wasp now that it is so widespread.

Is the fungal genus Ceratocystis experiencing a similar dispersal burst now? Australian authorities (Carnegie and Pegg 2018) have noted Ceratocystis wilts threatening Acacia and Eucalyptus, as well as Metrosideros.

Efforts often wane at the management and restoration stages.

In the cases of all three pathogens, governments have reduced their efforts once they determined that they could not eradicate the pest.

In North America, USDA APHIS regulates movement of nursery stock with the goal of preventing spread of P. ramorum to the East. The agency has reduced the stringency of its regulations several times over the 18 years it has been regulated. These changes have been made at the urging of the nursery industry in California and Oregon, which are where the pathogen is present. Two years ago, a major regulatory failure resulted in infected plants being shipped to more than 100 retailers in more than a dozen states. This had huge costs to dozens, if not hundreds, of nurseries and state regulatory agencies. Yet APHIS has neither published a straightforward and complete analysis of what went wrong, nor promised to correct any weaknesses revealed by such an analysis. Another apparent regulatory failure is the appearance of the EU1 strain of P. ramorum in the country; this seems to indicate that introductions to North America have occurred more recently than the initial introduction in the late 1980s or early 1990s.

In Hawai`i, concern about the potential impact of myrtle rust on the Islands’ dominant native tree species, ‘ōhi‘a (Metrosideros polymorpha), spurred action. Although myrtle rust spread to all the islands within months, the state imposed an emergency rule prohibiting importation to the state of Myrtaceae plants or cut foliage in 2008. This action was relatively rapid, although it was three years after detection of the pathogen. The rule aimed to prevent introduction of possibly more virulent strains. However, it expired in 2009 (emergency rules are effective for only one year).

Concerned about the possible impacts of various strains, the USDA Forest Service sponsored studies in Brazil. Based on their findings, Hawai`i adopted a new permanent rule in 2020. It prohibited importation of plants or foliage of all Myrtaceae species.

Also, APHIS proposed in November 2019 a federal regulation to support the state’s action through its NAPPRA authority. However, it took seven years to resolve regulators’ concerns about the possible presence and virulence of various strains. During this time importation of high-risk materials was not prohibited. As of this writing, it has been 18 months since APHIS proposed the NAPPRA listing, so federal rules still allow imports of high-risk material.

a surprisingly bad outbreak of rust on ‘ōhi‘a in 2016; cause unclear but possibly related to extremely wet weather; photo by J.B. Friday

Meanwhile, the focus of on-the-ground conservation and restoration efforts in Hawai`i has shifted to different pathogens, those causing rapid ‘ōhi‘a death dontmovefirwood.org

In Australia and New Zealand, federal officials determined within months of detection that myrtle rust was too widespread to be eradicated. They now focus on trying to prevent introduction of additional strains. Within the country, Australia prohibits movement of Myrtaceae (hosts of myrtle rust) to the two states so far free of the pathogen (South and West Australia). However, some scientists believe enforcement of these regulations is too lax. In New Zealand, nurseries are reported to be very careful to produce plants free of the pathogen. Is this sufficient?

The Australian government also funds seed collection and other ex situ conservation efforts. But little funding has been available even for impact studies. In Australia, funding from both state (New South Wales) and federal authorities became available only after designation of three plant species as endangered. The federal government also has not designated myrtle rust as a “key threatening process,” which would have opened access to significant funds and possibly prompted more vigorous regulatory efforts. The rust is included as part of the process “novel biota threat to biodiversity”, but scientists and activists consider this to be insufficient. A conservation strategy https://www.anpc.asn.au/myrtle-rust/ was developed by a coalition of non-governmental organizations and state experts. While never adopted by the federal government, this plan became the basis for a state strategy adopted by New South Wales in 2018 – eight years after the pathogen was first detected. For a thorough discussion of weaknesses in the Australian phytosanitary system’s response to the myrtle rust introduction, see Carnegie and Pegg 2018, full citation at the end of this blog.

In June 2021, the Australian Center for Invasive Species Solutions (CISS) and the office of the Chief Environmental Biosecurity Officer (CEBO) released a revised National Environment and Community Biosecurity RD&E Strategy. The sponsors sought feedback on the strategy from biosecurity and biodiversity researchers, investors, practitioners, the community, government and industry. Comments are due by 16 July 2021. The strategy is posted at https://haveyoursay.awe.gov.au/necbrdes

In New Zealand, the science plan for myrtle rust was described as advisory. The little funding available precludes resistance breeding and seed collection. There is not even a national program to track the rust’s spread.

Difficulties in Assessing Impact

Myrtle rust affects largely new growth of host plants, including flowers and seedlings and root sprouts. Thus, in many – but not all – host species the threat is primarily to reproduction rather than immediate mortality of mature plants. This delay in impacts complicates assessments of the threat posed by the rust.

NGO Action in Australia

After several years’ effort to build a broader coalition to support implementation of the NGO Action Plan, the Plant Biosecurity Science Foundation sponsored an international workshop in March 2021. The goal was to increase understanding of the rust and its impact and who is doing what. Time was devoted to discussions on how coordinate efforts to both raise awareness and spur government action. State and federal officials played prominent roles in both preparation of the Action Plan and the workshop – and did not shy away from criticizing Australia’s handling of the threat. The descriptions of myrtle rust’s impacts presented at the conference were much more dire than those of a few years ago. Information on impacts has accumulated slowly due to the few scientists doing the work. See https://www.apbsf.org.au/myrtle-rust/

Greater alarm about this pathogen is warranted.

Australia – Evidence of Disaster

According to speakers at the workshop, myrtle rust is causing an expanding disaster in Australia, where the flora is dominated by Myrtaceae. As of spring 2021, myrtle rust is widespread and well established in several native ecosystems in the eastern mainland states of New South Wales and Queensland and part of the Northern Territory. The disease has been detected in Victoria and Tasmania but impact is limited to urban gardens. It has not yet been detected in South or Western Australia. At this time, 382 of Australia’s Myrtaceae species – in 57 genera – are known to host the rust. Three species have been officially listed as critically endangered. Rhodamnia rubescens and Rhodomyrtus psidioides are formerly widespread understory trees in rainforests. Lenwebbia sp. is narrowly endemic, growing in stunted cloud forests on clifftops in a single mountain range. However, experts predict extinction of 16 rainforest species within a generation. (For comparison, only 12 plant species in Australia have become extinct since arrival of the first Europeans 200 years ago.) Several speakers at the conference stressed the speed at which rust is putting plant taxa in peril. Wetlands dominated by Melaleuca are apparently under immediate threat.

[For a thorough discussion of the rust’s impact on plant communities, see Carnegie and Pegg 2018, full citation at the end of this blog.]

New Zealand The vulnerability of each of the 27 – 30 native plant species remains unclear three years after the rust’s introduction.

New Caledonia The highly endemic flora of this small island group appears to be at great risk.

In Hawai`i, the rust has devastated one endangered plant species (Eugenia koolauensis) and damaged a non-endangered congener, E. reinwardtiana. The strain currently on the Islands does not threaten the dominant native tree species, ‘ōhi‘a (Metrosideros polymorpha).

Southern Africa

*Syzygium cordatum* South African plant in the Myrtaceae; photo courtesy of Bram van Wyk

South Africa has 24 native plant species in the Myrtaceae. I have been unable to learn the vulnerability of these species to the rust. South Africa relies heavily on plantation of Eucalyptus, some species of which might be vulnerable to the rust. The variant of the rust detected in South Africa 2013 is unique.

*Hetropyxis* sp. – South African plant in the Myrtacae; photo by Daniel L. Nikrent

Posted by Faith Campbell

SOURCES

Angus J. Carnegie, A.J. and G.S. Pegg. 2018. Lessons from the Incursion of Myrtle Rust in Australia. Annual Review of Phytopathology · August 2018

Jung, T.; Horta Jung, M.; Webber, J.F.; Kageyama, K.; Hieno, A.; Masuya, H.; Uematsu, S.; Pérez-Sierra, A.; Harris, A.R.; Forster, J.; et al.. The Destructive Tree Pathogen Phytophthora ramorum Originates from the Laurosilva Forests of East Asia. J. Fungi 2021, 7, 226. https://doi.org/10.3390/ open access!

Sudden Oak Death – two informative articles

I am alerting you to two publications about our “favorite” tree-killing pathogen, Phytopthora ramorum (sudden oak death).

SOD-infected rhododendron in a nursery in Indiana; photo by Indiana Department of Natural Resources

The Role of Nurseries in Spreading SOD

The first article informs the general public and raises important questions: “The Diseased Rhododendrons That Triggered a Federal Plant Hunt” by Ellie Shechet in The New Republic.

Ellie reviews the 2019 episode in which P. ramorum-infected rhododendron plants were shipped to retailers in the East and Midwest. Her article is based on interviews with state plant health and APHIS officials, several scientists and advocates (including me), and the executive director of the Oregon Association of Nurseries (OAN). Ellie notes that infected plants were found at more than 100 locations across 16 states.

Ellie notes that despite the risk to native plants in the eastern deciduous forest and the financial cost of implementing control actions (14 million plants were inspected in Washington State alone), plants have a “green” reputation; they are not recognized as potentially causing environmental harm.

The politics of the situation also are reviewed. She writes that the OAN representative has testified that he helped write the more relaxed regulatory approach that APHIS adopted by “federal order” in 2014 and formalized in changes to the regulations in 2019. APHIS denies this. [The article does not include the information that during this period, state regulatory officials detected P. ramorum-infected plants in between four and ten Oregon nurseries each year.] Ellie notes that individual consumers buying plants have few tools to try to ensure that plants they buy are not infected by SOD or other pathogens.

The fact is that the climate in the coastal areas of California, Oregon, Washington, and British Columbia is conducive to SOD, so the risk of diseased plants being produced there and sold is constant. The current APHIS regulations do not adequately address this, in my view!

Science: High Risk of Phytophthora Introductions from Southeast Asia

The second article reports results of intense scientific effort: Thomas Jung, Joan Webber, Clive Brasier, and other European plant pathologists report more completely on searches for P. ramorum and other Phytophthora species in East Asia. See the full citation at the end of this blog. [I blogged about their preliminary report a little over a year ago.] Jung et al. conclude that P. ramorum probably originates from the laurosilva forests growing in an arc from eastern Myanmar, across northern Laos, Vietnam, and southwestern China (Yunnan) to Shikoku & Kyushu islands in southwest Japan. The article notes that two other Phytophtoras – P. lateralis (cause of fatal disease on Port-Orford cedar) and P. foliorum – appear to be from the same area. Field science by this team has found 38 previously unknown Phytophthora species in these same forests – and expect that more are present.

Clive Brasier in Vietnam; UK Forestry Research

They warn that the lack of information about potential pathogens in many developing countries presents a high risk of introduction to naïve environments through burgeoning horticultural trade – especially since the World Trade Organization requires that a species be named and identified as posing a specific threat before phytosanitary regulations can be applied. [I addressed the issue of international phytosanitary rules in Fading Forests II; see the link at the end of the blog.]

Other Pathogen Risks from the Region

Phytophthoras transported on imported plants are not the only pathogens that could come from Asia. The vectors and associated pathogens causing laurel wilt disease across the Southeast and Fusarium disease in California are believed also to originate in the same region of Asia. Unlike the Phytophthoras, which are transported primarily through the trade in plants for planting, these fungi travel with the vector beetles in wood packaging material. U.S. imports of goods from Asia – often packaged in wooden crates or pallets – have skyrocketed since July 2020. The ports of Los Angeles-Long Beach, which receive 50% of U.S. imports from Asia, handled 6.3 million TEU (twenty-foot equivalent containers) from Asia during the period July 2020 through February 2021. The average of close to 800,000 TEU per month for eight consecutive months is unprecedented. Other ports also saw increased import volumes from Asia during this period. [I discussed these shifts in my blog in January.] Imports from Asia in 2020 accounted for 67.4% of total US imports from the world. Imports from China specifically accounted for 42.1% of total US imports. [Data on import volumes is from several reports posted by the Journal of Commerce at its website: https://www.joc.com/maritime-news/]

SOURCE

Posted by Faith Campbell

Decision!! California Department of Food & Agriculture Upgrades Ranking of Phytophthora occultans

In January 2021, the California Department of Food and Agriculture announced the pest rating for Phytophthora occultans, one of two species of Phytophthora it was reviewing. (Once at the website, click on “comment” – next to name Heather Sheck.)

I blogged about this action in December.

Five people or organizations submitted comments. The most comprehensive comments were submitted by Elizabeth Bernhardt, Ph. D. and Tedmund Swiecki Ph.D. of Phytosphere Research. Another scientist was Tyler Bourret, who had been the first to detect P. occultans in California when working as a student in 2015-16. The third scientist was Jennifer Parke, a plant pathologist at Oregon State University who has worked with Phytophthora species in agriculture and wildland settings for 36 years. Additional comments were submitted by the Phytophthoras in Native Habitats Work Group and me.

All commenters raised some issues. First was the lack of information on the true distribution of P. occultans in California. CDFA restated that it that relies on official records and survey information, and that those records support a “low” rating.

Several issues relate to the definitions that CDFA applies in assigning ranks. They are so restrictive that – in my view – they result in underestimates of pathogens’ potential impacts.

One example is how CDFA recognizes first detections of a pathogen. As Bernhardt and Swiecki point out, CDFA’s consideration of only “official” samples prevents timely action to protect California’s agriculture and native vegetation. In the case of P. occultans, CDFA took no action for two years after the pathogen was first reported in the state. This detection had been confirmed by a CDFA laboratory.

A second example is host range. CDFA says it assigns a host range rating of “wide” (rating of “3”) only to pathogens that have host ranges of hundreds of species. This means that pathogens with dozens of known hosts across several plant families are given a ranking of “moderate” (2). Furthermore, the agency considers only “official” samples in defining hosts. This approach precludes consideration of the high probability that additional hosts would be found in future, including federally listed species in the genera Ceanothus and Arctostaphylos. Bernhardt and Swiecki named two additional hosts based on field work. CDFA responded to the second point by adding a reference to the likely expansion of the host range in the “Uncertainty” section of the document.

Similarly, CDFA gives a reproductive potential rating of “3” only to pathogens spread by a vector or that infect seeds.

CDFA staffers who manage specific pests lack authority to change these too stringent ranking criteria. The agency leadership need to adopt more realistic criteria.

CDFA responded by accepting many of the additional factors raised primarily by Bernhardt and Swiecki. This resulted in raising the overall score from 11 to 14, and changing the ranking from “C” to “B”.

Posted by Faith Campbell

Let’s shape the Biden Administration’s & New Congress’ Policies on Non-Native Forest Pests!

We have a great opportunity to shape future efforts to counter non-native forest pests and diseases. Administration officials are most open to new ideas when they first take office. The same is true of new Congressional leadership.

So now is the time to suggest needed changes!

The USDA Secretary-designate is Tom Vilsack. Of course, he was USDA Secretary during the Obama Administration … so he is not entirely “new” to the issues. However, perspectives and priorities have changed, so now is a good time to urge him to consider new approaches. Furthermore, the Senate Agriculture Committee will hold confirmation hearings for him; we can ask the Senators to advocate for our views during this proceeding.

The House Agriculture Committee has a new Chair, David Scott – from the suburbs of Atlanta, Georgia. Again, this provides an opportunity to suggest new approaches and topics for hearings.

I assume you all are knowledgeable about the numbers and impacts of non-native forest insects and pathogens in the United States, and of the pathways by which they are introduced and spread. If you are not, peruse my blogs about wood packaging or plants as vectors (click on the appropriate “categories” listed at the bottom of the archive of blogs). Or read Fading Forests III (see the link at the end of this blog) and the article I coauthored early this year on improving forest pest management programs.

On the basis of my long experience, I suggest that you encourage USDA Secretary-designate Vilsack, Senators on the Agriculture Committee, and House Agriculture Committee Chair David Scott to consider the following recommendations:

Actions Congress could take

Congress could amend the Plant Protection Act [7 U.S.C. §7701, et seq. (2000)] to prioritize the protection of natural and agricultural resources over the facilitation of trade. This might be done by amending the “findings” section of the statute to give higher priority to pest prevention.
The Agriculture Committees of both the House and Senate could hold hearings on the importation of forest pests. They could determine if the USDA is doing an adequate job protecting the country from insect pests and diseases, and how our defenses could be strengthened. One component of the hearings could focus on whether current funding levels and mechanisms are adequate to support vigorous responses to new pest incursions.
Congress could commission a study of the feasibility, costs and benefits of establishing a “Center for Forest Pest Control and Prevention” to coordinate research and policy on this issue.
Congress could increase funding for the appropriate USDA APHIS and Forest Service programs and activities to enable vigorous containment and eradication responses targeting introduced forest pests and diseases.
Congress could increase funding for USDA research on detection of insects and pathogens in shipping; insect and disease monitoring/surveillance; biological control; alternatives to packaging made from wooden boards; management of established pests; and resistance breeding to enable restoration of impacted tree species.

Actions Secretary-designate Vilsack could initiate without legislative action (once he is confirmed)

Introductions of pests in the wooden crates, pallets, etc., goods come in

APHIS could take emergency action to prohibit use of wood packaging by importers of goods from countries with a record of poor compliance with ISPM#15. This action is allowed under authority of the Plant Protection Act [7 U.S.C. §7701, et seq. (2000)] and Article 5.7 of the World Trade Organization’s Agreement on the Application of Sanitary and Phytosanitary Measures.
APHIS could strengthen enforcement of current regulations by aggressively prosecuting repeat offenders. For instance, APHIS could begin imposing administrative financial penalties on importers each time their wood packaging is non-compliant with ISPM#15.
APHIS could work with Department of Homeland Security Bureau of Customs and Border Protection (CBP) to improve information available to U.S. importers about which foreign suppliers of SWPM and shippers have good vs. bad records of compliance with ISPM#15.
DHS CBP could release information on country of origin and treatment facility for ISPM#15-stamped SWPM that is found to be infested with pests.
USDA APHIS could begin a phased transition from solid wood packaging to alternative materials that cannot carry wood-boring pests. APHIS could initiate a pest risk assessment to justify making such an action permanent. Imports could be packaged in alternative materials, e.g., manufactured wood products (e.g. plywood), metal, or plastic.

Nursery Plant (“Plants for Planting”) Pathway

APHIS could apply authorities under NAPPRA and other existing authorities to curtail imports of plants that pose a high risk of introducing insects and pathogens that would threaten tree species that are important in natural and urban forests in the U.S. At a minimum, APHIS should restrict imports of live plants that are in the same genus as native woody plants of the U.S.
APHIS could work with the Agriculture Research Service and National Institute of Food and Agriculture to determine which taxa of woody vegetation native to the U.S. are vulnerable to pathogens present in natural systems of trade partners. Particularly important would be the many Phytophthora species found by Jung and colleagues in Vietnam, Taiwan, Chile, and other countries. Once the studies are sufficiently complete, APHIS could utilize authority under NAPPRA to prohibit importation of plants from those source countries until effective phytosanitary measures can be identified and adopted.

Other Actions

APHIS could develop procedures to ensure the periodic evaluation of pest approach rates associated with wood packaging and imports of “plants for planting” and highlight areas of program strengths and weaknesses. A good place to start would be to update the study by Haack et al. (2014), which estimated the approach rate in wood packaging a decade ago.
The USDA could expand early detection systems for forest pests, such as the APHIS CAPS program and the Forest Service EDRR program. These programs should be better coordinated with each other and should make better use of citizen observations collected through smartphone apps, professional tree workers such as arborists and utility crews, and university expertise in pest identification and public outreach. An effective program would survey for a broad range of pests as well as for suspicious tree damage, and would be focused on high-risk areas such as forests around seaports, airports, plant nurseries, and facilities such as warehouses that engage in international trade.
The USDA could initiate a “Sentinel Plantings“ network of US tree species planted in gardens abroad and monitored for potential pests and diseases.

Posted by Faith Campbell