Month: January 2022

Interactions of 2 (of 3) Threats to Beech

American beech (Fagus grandifolia) is a widespread and beautiful tree of the eastern deciduous forest. Its range reaches from Nova Scotia to eastern Wisconsin, then south to Mississippi and Louisiana and east to mid-Georgia. It is an important food source for 40 wildlife species, particularly in the northern parts of its range where few other species produce hard mast. (See Lovett et al. 2006.)

Threats

Unfortunately American beech is under threat from three non-native organisms or complexes: 1) beech bark disease, 2) beech leaf disease, and 3) beech leaf mining weevil. A fourth pest, a previously unknown – and still unnamed bark beetle in the genus Agrilus – has been detected in New York City on European beech trees. It is not yet known whether it will attack American beech and, if so, whether it will also cause serious damage (Michael Bohne, USFS, pers. comm.)  

symptoms of beech bark disease; photo by Linda Haugen, USFS; via Bugwood

Beech bark disease (BBD) results from the interaction of the introduced European beech scale insect (Cryptococcus fagisuga) and several fungi in the Neonectria genus – some of which are also introduced. The resulting disease has been killing American beech trees since the beginning of the 20th Century. It has spread from Nova Scotia to much of the tree’s range. It has dramatically altered the composition and structure of stands containing beech.

symptoms of beech leaf disease; photo provided by Jennifer Koch, USFS

Beech leaf disease (BLD) was initially detected in 2012, near Cleveland. As of December, 2021, it has spread due east across New York, Pennsylvania, and New Jersey to the Atlantic, then up the coast through Connecticut and eastern Massachusetts, with a separate outbreak in central Maine. The disease is apparently associated with a nematode, Litylenchus crenatae ssp. mccanni, although additional pathogens, like bacteria, might also play a role. The origin of the North American population of the nematode is unknown; it is a related but separate subspecies from a Japanese nematode (Reed et al. 2022).

American beech defoliated by leaf mining weevil; photo courtesy of Jon Sweeney, CFS

Beech leaf mining weevil (Orchestes fagi) is, so far, limited to Nova Scotia. However, it is expected that the weevil will continue spreading throughout the range of American beech through both natural dispersal and human-assisted movement. Repeated defoliation by the weevil might increases mortality rates in forests that are surviving in the “aftermath” stage of BBD (Sweeney et al. 2020).

A new study (Reed et al. 2022) concludes that, despite being detected only 10 years ago, BLD has already become pervasive in forests surrounding Lake Erie in the U.S. and Ontario. While somewhat more prevalent in U.S. states on the eastern side of the Great Lakes (on 54% of trees) than in Ontario (on 46% of trees), BLD is spreading rapidly and affecting every canopy layer. Mortality is highest in seedlings and saplings; understory saplings die within 2 – 5 years. The occasional mortality of overstory trees occurs within seven years of [observed] infection. Defoliation and mortality of saplings allow more light to pass through to the understory; this is expected to alter plant communities on the forest floor.

Beech scale is more widespread in Ontario (found on 60% of trees) than in the U.S. (38% of trees). This is not surprising since the scale was detected in Ontario in 1960, 24 years before it was detected in portions of Ohio, New York and Pennsylvania included in the study (in 1984). Throughout this region, beech scale is disproportionately affecting overstory trees.

Only 4% of trees throughout the study area are infected with Neonectria cankers. In other words, full-scale beech bark disease is not yet widespread and is spreading surprisingly slowly. Scientists do not understand this phenomenon.

These findings are based on a network of monitoring plots a network of monitoring plots set up in 2019 set up in areas surrounding the Great Lakes. They comprise 34 plots at 17 locations in southwest Ontario and 30 plots at 25 locations in Ohio, Pennsylvania, and New York. In total the plots hold 646 live American beech trees — 412 saplings; 85 in the intermediate/suppressed (subcanopy) category; and 149 in the dominant/codominant (canopy) class.

Forest composition is similar throughout the study area. The most common species in association with American beech are sugar and red maples (Acer spp.), and white and green ash (Fraxinus spp.). Other tree species present include eastern hemlock (Tsuga canadensis), white pine (Pinus strobus), oaks (Quercus spp.), and birches (Betula spp.). Study plots had few invasive plants – although the invasive species present are well-documented to invade forests.

Ontario disease assessment

In Ontario, BLD was identified in 25 of the 34 plots.  It was present on 171 saplings, 53 intermediate trees, and 70 dominant trees. Both prevalence and severity were greatest on intermediate trees. Beech scale was present at all 34 plots. While scales were found on trees of all sizes, they were almost two times more prevalent and were more severe on mature trees than saplings. Neonectria cankers were detected at 34 plots. Neonectria was rare but most severe on dominant trees. Fewer than one third of saplings and one-sixth of mature trees were pest free.

U.S. disease assessment  

BLD was present in 17 of the 30 plots. It was found on 75 saplings, 30 intermediate trees, and 38 dominant trees. Saplings and dominant trees had similar levels of disease; intermediate trees had significantly less. However, BLD severity was twice as high on saplings compared to mature trees. BLD was present on more than half of the seedlings assessed – 46 out of 82. Beech scale was present in 20 of the 30 plots. It was significantly less common and severe on saplings than on mature trees. Neonectria cankers were present in only 4 of 30 plots. Canker prevalence and severity did not differ significantly among size classes.

Distribution and Effects of Beech Scale and BBD

While beech scale attack facilitates invasion by the Neonectria fungi, the disease – BBD complex – had the most limited distribution of the three pests in this study. It was found on only ~4% of beech trees throughout the study area. The disease was first reported there in the early 2000s. Although no one knows why, it has spread more slowly there than in areas to the east (Reed et al. 2022).

As is the case with beech scale, BBD disproportionately affects large diameter trees. Typically, BBD kills more than half of mature beech within 10 years of its arrival. Dying trees produce prolific root sprouts resulting in dense beech sapling understories that impede regeneration of less shade-tolerant tree species. The persistence of thickets of disease-vulnerable small beech perpetuates the disease. BBD is the only forest disease in North America that can inadvertently intensify itself by increasing densities of its host while suppressing other species.

Beech Forest Community Change in Response to Combined Impacts of BBD and BLD

It is unclear how forests will change as beech die. Some expect saplings of species already present — red maple, white ash, and, especially sugar maple — to exploit the canopy gaps. Of course, white and green ash are under attack by the emerald ash borer; DMF their ability to reach the canopy will depend on the success of biocontrol agents.

However, if BBD or BLD resistant beech survive or if BLD fails to persist, future forests might instead consist of beech thickets that would prevent all but the most shade tolerant species from establishing. Heavy deer predation on maple seedlings and saplings might also play a role. A third possibility is that morbidity from BBD and BLD might lead to uneven-aged conditions that allow younger trees — perhaps even shade intolerant species e.g., oaks — to establish.

Invasive plants also have the potential to fill gaps left by declining beech. While maple-beech forests often have sparse understories due to low understory light levels, pest-caused canopy gaps are expected to increase the abundance of invaders, especially in small woodlots and forests near urban areas. Several shade-tolerant invasive shrubs are already present in low numbers: Japanese barberry (Berberis thunbergii), tatarian honeysuckle (Lonicera tatarica), multiflora rose (Rosa multiflora), and buckthorn (Frangula sp.). Reed et al. (2022) note that these species, plus privet and autumn olive, can take advantage of small canopy gaps, especially when soils are disturbed, e.g., by active intervention to counteract the loss of beech.

Precautionary Research and Management

Reed et al. (2022) call for enhanced monitoring of beech forests focused on

  • the timing of BLD presence relative to tree age and size – which might affect competitiveness of sprouting beech in the understory; and
  • compositional and structural change in forests with BLD or to which it is likely to spread

They also recommend abandoning the management approach for BBD currently recommended by foresters. It calls for removing scale-susceptible beech so that resistant genotypes increase in prevalence. In forests with both BBD and BLD, they conclude, management of natural regeneration is unlikely to succeed because BLD will kill sprouts and saplings that might be resistant to scale. They recommend instead active management of the forest to promote mast-producing, shade intolerant species, such as oaks and hickories.

They also recommend increased support for resistance-breeding programs. Such programs already target BBD, based on the estimated 1% of American beech that show some resistance. Now those programs need to incorporate BLD resistance. (Reed et al. note that small numbers of beech show few or no BLD symptoms so might possess resistance or tolerance.)

grafted beech for resistance breeding; photo by Rachel Kappler, then USFS (now Great Lakes Basin Initiative & Holden Arboretum)

Unfortunately, the Canadian beech breeding program’s future funding is highly uncertain. To counter this threat, in part, Reed et al. (2022) suggest cryopreserving beech embryos from Canada to develop a beech conservation collection that would be available for a more robust, future Canadian breeding program. The USFS is trying to develop methods to screen trees for resistance to BLD, specifically to the nematode (J. Koch, USFS, pers. comm.)

Another approach would actively manage beech stands in which potentially BLD-resistant beech grow to help these trees reach the canopy and reproduce. In the absence of management, any BLD-resistant beech seedlings might be overtopped by faster growing, shade-intolerant species – especially if the gaps promote soil drying or sun scald.

Finally, breeding programs need to factor in the beech leaf mining weevil, DMF which — as I noted in the beginning — is spreading across Nova Scotia and could spread to the rest of the native range of beech (Sweeney et al., 2020).

The Department of Agriculture has created a website on the Department’s plant-breeding efforts. It includes a subwebsite on USFS efforts. However, I did not find much useful information there.

SOURCES

Lovett, G.M., C.D. Canham, M.A. Arthur, K.C. Weathers, and R.D. Fitzhugh. 2006. Forest Ecosystem Responses to Exotic Pests and Pathogens in Eastern North America. BioScience Vol. 56 No. 5 May 2006)

Reed, S.F., D. Volk, D.K.H. Martin, C.E. Hausman, T. Macy, T. Tomon, S. Cousins. 2022. The distribution of beech leaf disease and the causal agents of beech bark disease (Cryptoccocus fagisuga, Neonectria faginata, N. ditissima) in forests surrounding Lake Erie and future implications Forest Ecology and Management 503 (2022) 119753

Sweeney J.D., Hughes, C., Zhang, H., Hillier, N.K., Morrison, A. and Johns R. (2020) Impact of the Invasive Beech Leaf-Mining Weevil, Orchestes fagi, on American Beech in Nova Scotia, Canada. Frontiers in Forests and Global Change | www.frontiersin.org 1 April 2020 | Volume 3 | Article 46

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

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

Breeding Pest Resistance in Trees – Thoughtful Perspectives

Scott Schlarbaum collecting butternuts; photo by F.T. Campbell

I have blogged several times about the need to enhance efforts to breed trees resistant to the most damaging of the hundreds of introduced insects and pathogens. Others concur – see reports by the National Academy of Sciences in 2018; several publications by USFS scientists Richard Sniezko and Jennifer Koch; a workshop hosted by Purdue w/ USFS support, the creation and efforts of several consortia – Whitebark Pine Ecosystem Foundation, Great Lakes Basin Forest Health Collaborative, Forest Restoration Alliance …

Also, Richard J. A. Buggs, of the Royal Botanic Gardens, Kew, recently summarized barriers to tree breeding. It was published as an especially thoughtful editorial in Plants People Planet in anticipation of the International Year of Plant Health in 2020 (see reference at the end of this blog). That issue included several related articles, also noted below.

 R.J.A. Buggs’ Perspective on Tree Breeding

Buggs says the need for tree resistance research is greater than ever before. First, damage caused by introduced insects and pathogen is rising. Plus, we now recognize trees’ importance in capturing atmospheric carbon. He sees encouraging signs of growing public awareness of both factors. Also, he thinks citizen science might reduce the cost of some activities … although he doesn’t name which they are.

Dr. Buggs lists six major hindrances to breeding programs, including some aspects that I, at least, have not considered:

1) Trees’ size and long generation times mean research is necessarily slow. One result is it is hard to formulate research proposals that match funding cycles. This in turn means a dependence on long-term institutional commitment from well-funded organizations, and such institutions are rare.

I point out that the U.S. government – especially the USFS – is one such institution. Unfortunately, it has so far been reluctant to take commit major resources to breeding pest-resistant trees. Every year I urge you to lobby Congress on appropriations for the agency. In this context, do you understand that while the USFS Research budget receives approximately $300 million each year, less than $5 million of that total is allocated to researching invasive species (of all taxa)? Some gaps are filled by projects funded by the Forest Health Program. You will have a new opportunity to lobby Congress for Fiscal Year 2023 in the spring!

2) On the other hand, reliance on long-term institutional funding shelters projects from multidisciplinary peer-review that could introduce improved technology or methods. This lack of peer review also contributes to a perception among other scientists that tree resistance research is a scientific backwater.

3) Similarly, studies requiring a long time horizon don’t fit publication schedules. Again, the result is that the findings often appear only in institutional reports or conference proceedings. This means they are hard to find and often lack external peer review at not only the proposal stage but also before publication.

4) The long decades without clear success in dealing with Dutch elm disease (but see recent encouraging developments here) and chestnut blight (see The American Chestnut Foundation here) gave the impression that resistance breeding of forest trees is impossible. Buggs says pest resistance problems are easier to tackle for other trees.

TACF American chestnut; photo by F.T. Campbell

5) Those considering what efforts to fund might demand complete resistance to the pest. This goal is not only unrealistic – it is often unnecessary. Often lower levels of resistance or tolerance can result in trees that can be self-sustaining. Dr. Sneizko concurs; see his article appearing in this issue.

6) Forest stakeholders differ over the goal of developing resistant trees. Some think any human intervention is unwarranted in wilderness areas. Some want a tree as similar as possible to pre-epidemic trees. Others want a tree that produces more timber.

Other Significant Articles

A second article in the same issue of Plants People Planet (Federman and Zankowski) discusses the USDA’s commitment to new approaches in tree resistance research.

I found a third article that discusses British approaches to mitigating tree pests to be more informative than Federman and Zankowski – although somewhat worrying. Spence, Hill and Morris praise the U.K.’s Plant Health Risk Register, which they say has enhanced vigilance on possible new pest introductions. However, the authors describe resistance breeding as a strategy to be considered “when a pest has established such that a tree population is unable to recover, and where a genetic basis for resistance is demonstrable in a proportion of the tree population.” Dr. Sneizko, and others – and I!  – call for initiating exploration of the potential for resistance breeding much earlier in an invasion.

A fourth article – by Richard Sniezko and colleagues —  describes encouraging levels of partial resistance to white pine blister rust in two western white pines and evidence for both qualitative and quantitative resistance to Phytophtohora lateralis in Port-Orford Cedar.

Port-Orford test seedlings; photo courtesy of Richard Sniezko

A fifth – by Showalter et al. — reports encouraging levels of resistance to both emerald ash borer DMF and ash dieback in European ash. The authors conclude that a breeding program might be a viable solution to both pests.

SOURCE

Special issue of Plants People Planet for 2020  — the International Year of Plant Health. https://nph.onlinelibrary.wiley.com/toc/25722611/2020/2/1

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

An Evaluation of Canadian Invasive Species Efforts

A group of scientists has published a report on Canada’s invasive species programs (see reference at the end of this blog). It compares the structures and procedures of Canada’s federal government to those in the U.S., Australia, and New Zealand.

The report focuses on proactive measures aimed at preventing introductions, including cross-border introductions from the U.S. It does not describe efforts to prevent spread between provinces. Nor does it address efforts by provincial or territorial governments, Tribes, or non-governmental organizations (NGOs).

The authors seek to understand how federal infrastructure, strategies, and decisions have contributed to outcomes. Their principal recommendation is that Canada should accord protecting biodiversity as much importance as preventing direct economic impacts from invasive species – unlike now and in the past. Those economic impacts are substantial, estimated at $34.5 billion (Canadian) each year.

The authors think that such a focus is appropriate because Canadians depend on the stability and function of a wide range of ecosystems and express strong interest in protecting their environment. Canada has also accepted obligations to protect biological diversity by joining the Convention on Biological Diversity (CBD). One of those obligations was that, by 2020, the country would have put in place plans targetting high risk species and pathways of introduction..   

The report notes that Canada faces some unique challenges: three coastlines, the intimate relationship with the U.S. (i.e., a long border and diverse shared water bodies), vast area, and very low human population density. The last might result in fewer incidents of human-mediated dispersal. However, it is likely to present logistical challenges in detecting and managing any invaders. In addition, common, popular Canadian recreational activities — camping, boating, and fishing — can contribute to invasive species’ introduction and spread.

hemlock mortality due to hemlock wooly adelgid in Nova Scotia; HWA had spread from the U.S. Photo courtesy of Celia Boone, NS Department of Land and Resources

Canada’s Biosecurity Efforts

Canada adopted its Invasive Alien Species Strategy in 2002. The plan addresses four stages of invasion: 1) prevention of new introductions; 2) early detection of newly introduced species; 3) rapid response to new invaders; and 4) management of species that are established and spreading.

The report laments that Canada lacks centralized oversight of it biosecurity efforts in preventing new introductions across all pathways. That is, responsibilities are divided among several agencies, depending on the associated commodity or resource. One result is that similar pathways are regulated differently. One example is ship-mediated vectors. Ballast water is strictly regulated by both Canadian regulations and the 2004 Convention for Control and Management of Ship’s Ballast Water and Sediments (which took effect in 2017). However, commercial fishing and recreational boats are not federally regulated.

In accordance with the CBD, the Canadian government submitted a report in 2018, claiming to be on track to achieve its 2020 targets. The government had identified priority pathways: shipping, horticulture, aquarium/pet trade, transport containers, road construction, and recreation (e.g., boating). Several had been regulated at least partially, including wood packaging, forestry products, and plant products.  Legislative and regulatory tools had been strengthened, including risk assessments and management plans for ballast water, recreational boating, and wood packaging. (I cannot explain the conflicting assessments of the regulation of recreational boating.) Also, national plans had been developed for several priority species, including the Asian subspecies of Lymantria dispar and emerald ash borer. The country acknowledged gaps with regard to emerging animal diseases, the pet trade, and dispersal across the U.S. border.

Comparing Canada to Other Countries (see Table 2)

The United States: I am disappointed by the report’s comparison of Canadian and U.S. invasive species programs because it considers formal structures rather than how the programs work in reality.  The Canadian report allots much greater authority to the U.S.’ interagency National Invasive Species Council (NISC) than I think it actually enjoys.

The report notes the abundance of U.S. data on invasive species’ distribution and hosts. It cites specifically the USDA Forest Service Forest Inventory Analysis. It also notes the importance of several transborder non-governmental organizations, including North American Invasive Species Management Association (NAISMA) and EDDmaps and binational entities such as the Great Lakes Fishery Commission.

Australia: The Canadian report praises the existence of an Inspector-General of Biosecurity who conducts independent reviews of biosecurity issues. It also applauds the coordinating role of the Intergovernmental Agreement on Biosecurity, which sets roles, responsibilities and governance agreements for biosecurity responses at all levels of government. Finally, it notes that the Department of Agriculture, Water and Environment (DAWE) created a National Priority List of Environmental Pests, Weeds and Diseases. 

I have no independent understanding of how successful Australia has been in addressing invasive species. However, several forest health experts appear to have been dissatisfied with the country’s response to the introduction of Eucalyptus rust; see my blog.

New Zealand:  Again, the report praises centralization of policy and government efforts in the Ministry for Primary Industries (MPI) under the provisions of the Biosecurity Act of 1993. The MPI advises the Minster for Biosecurity – which has no counterpart in the government of Canada. The report also notes that while New Zealand expects landowners and individuals to manage their own biosecurity risks, they can claim compensation if they suffer loss due to a biosecurity action, e.g., destruction of nursery stock. The Canadians think this provision might encourage people to report invasive species. New Zealanders are trying to create an all-citizen “team” to address invasive species. One way they promote this idea is to issue awards recognizing individuals’ efforts.

I wish the Canadian report had also looked at South Africa, which has done such a good job in its invasive species reports.

Four Case Studies

The report includes four case studies: a “historical failure”, a “historical success”, and two substantial current threats.

Preventing introductions of zebra and quagga mussels is described as a “historical failure”. There was no relevant preventive measure in place at the time they were introduced. Since preventive measures were made compulsory, no invasive species have been documented as becoming established in the Great Lakes via the ballast water pathway. Such introductions have occurred in less well-regulated marine systems.

Eradication of the Asian longhorned beetle (ALB) is described as a “historical success”. The initial Toronto outbreak was not completely eradicated; a small residual population was detected about a decade later and eradicated then. The report notes that the Toronto outbreaks were noticed by citizens rather than the relevant government agency. So “success” is attributable to chance and astute citizens rather than rigorous enforcement. I note that most U.S. detections of wood borer infestations are also detected by citizens. It is probably unrealistic to expect all detections to result from official programs.

The threat to Canada from the spotted lanternfly (SLF) is high since it could cross the land border from the U.S. Its principal host, Ailanthus, is widespread in southern Canada – not just in the East but also in Saskatchewan and Alberta. The insect’s egg masses are easily transported on a wide variety of vehicles. The report does not enumerate how many trucks or trains cross the border each year. The report laments that Canada has not adopted a clear monitoring plan aimed at detecting early SLF introduction.

Finally, four species of carp native to Asia threaten to invade the Great Lakes, for example through the Chicago canal or Sandusky River. Canada has asked citizens to be on the alert, and is exploring use of eDNA monitoring systems.

Lessons and Recommendations

The report highlights lessons learned in its four-country review and makes a series of recommendations:

1) Value biodiversity as well as economic and industrial interests.

The Canadian Species at Risk Act (its endangered species legislation) does not mention invasive species as a cause of endangerment. The Natural Sciences and Engineering Research Council now provides a centralized repository of biodiversity monitoring data which will help overcome data limitations associated with invasive species surveillance and risk modelling.

2) Consolidate regulatory frameworks

Canada should follow Australia and New Zealand in assigning a single body to be responsible for biosecurity. It should set biosecurity priorities, coordinate research and management at various government levels, and lay the groundwork for consistent actions.

3) Strengthen partnerships with the public and Indigenous communities

The report’s authors praise New Zealand’s efforts to engage all citizens in biosecurity. Canada would benefit from enhanced educational efforts – which are stronger now thanks to the growing availability of phone apps. Canada should ensure that Indigenous communities’ perspectives and knowledge are integrated into the program.

4) Strengthen partnerships with other countries

Canada should prioritize discussion of biosecurity with its trading partners, particularly in developing multinational trade agreements.  This is a key improvement that the U.S. could make, too.) It is particularly important to strengthen collaboration with the U.S.

4) Adapt to future conditions

Canada will need to anticipate changes due to population increase and climate change. Research needs to recognize and overcome current taxonomic and geographic biases. Also, research should focus on developing new technologies and treatment techniques proactively, before they are needed. One area of concern will be migration corridors (or “assisted migration”) undertaken to protect biodiversity as the climate changes.

5) Anticipate conflict

The government must expect different perspectives among stakeholders. Greater transparency in education campaigns might help prevent disagreements from becoming serious barriers to action.

SOURCE

Reid CH, Hudgins EJ, Guay JD, Patterson S, Medd AM, Cooke SJ, and Bennett JR. 2021. The state of Canada’s biosecurity efforts to protect BD from species invasions. FACETS 6: 1922– 1954. doi:10.1139/facets-2021-0012 Published by: Canadian Science Publishing   

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

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.

Rep. Peter Welch

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:

  1. The Constitution gives primacy to federal agencies in managing imports and interstate trade.
  2. Only a consistent approach can protect trees (and other plants) from non-native pests that spread  across state lines.
  3. 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.

areas at risk to goldspotted oak borer

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

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

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

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

Wood packaging – Progress? or Paralysis by Analysis?

This February marks 16 years since APHIS began full implementation of ISPM#15. I have blogged often about the failure of ISPM#15 to curtail the risk associated with wood packaging; scroll below the chronological list of blogs to the “categories”, click on “wood packaging”.  The best summary of the issues is found in a blog posted in September 2017.

As I have reported in many previous blogs, U.S. imports – especially those from Asia – have been rising since August 2020. Thus, January through October 2021, U.S. imports from Asia are 10.5% higher than the same period in 2020 (Mongelluzzo Dec. 9, 2021). Port officials expect import volumes from Asia to remain high in the first half of 2022, with perhaps a pause in February linked to Asian New Year celebrations (Mongelluzzo Dec. 15 2021). Shipping tonnage devoted to carrying goods from Asia to North America rose by 17% when one compares 2020 to 2021 (Lynch and Wadekar 2021).

These increases are important because of the history of pest introductions in wood packaging from Asia.

This increase is seen most acutely at the ports of Los Angeles and Long Beach, which handle about 50% of all U.S. imports from Asia. Such imports during January – November 2021 were 19.4% higher than the same period in 2020; 21.2% higher than during the same period in 2019 (Mongelluzzo Dec. 15 2021).

The rise in imports – and associated pest risk — is not limited to southern California. At the largest port on the East coast – New York/New Jersey – import volumes through October were 20% higher than the same period a year ago. The port is also receiving a higher number of large ships – those carrying 9,000 or more containers (Angell Dec. 22, 2021).

We do not know how many of these containers hold the heaviest commodities most often associated with wood packaging infested by insects — machinery (including electronics); metals; tile and decorative stone (such as marble or granite counter tops). I see many potential links to the COVID-prompted “home improvement” boom. I wonder whether furniture should be included here … 

wood packaging associated with stone; photo courtesy of Canadian Food Inspection Agency

1. 2021 Data on Violations

A recent webinar sponsored by The Nature Conservancy’s Continental Dialogue on Non-Native Forest Insects and Diseases and the Entomological Society of America revealed important new information on the pest risk associated with these imports. (Presentations have been posted on the Dialogue’s website). Several of the presentation have particularly significant implications for protecting the US from pests.

Jared Franklin, acting director for agriculture enforcement for DHS’s Customs and Border Protection (CBP), reported that pest detections and shipper violations in Fiscal Year (FY) 2021 follow patterns set earlier. There is, however, an interesting decline in numbers of violations despite enhanced inspection intensity. When the number of incoming air passengers crashed because of COVID-19, CBP assigned inspectors to cargo instead.

Type of violationFY2018FY2019FY2020FY2021
Lack ISPM#15 mark1,6621,8251,6621,459
Live quarantine pest found756747509548
TOTAL VIOLATIONS2,4182,5722,1712,007

Unfortunately, in FY2016 CBP stopped recording whether pests were detected on marked or unmarked SWPM.

As usual, most of the pests were detected in wood packaging accompanying miscellaneous cargo. Also, as usual, the most commonly detected pests are Cerambycid beetles. During a discussion of why Cerambycids outnumber Scolytids, Bob Haack pointed out that most bark beetles are eliminated by the debarking required by ISPM#15.

2. Updating a Key Study of the Wood Packaging Pathway

Bob Haack revealed that he has received permission to update his earlier landmark study aimed at determining the arrival rate of pests in wood packaging (see Haack et al., 2014). I have long advocated for an update. All my comment about the wood packaging risk have – perforce – relied on this now outdated report. Bob hopes to have results in a few months.

This time, he will work with Toby Petrice (USFS) and Jesse Hardin and Barney Caton (APHIS). While the 2014 study focused on changes in approach rates resulting from U.S.’ implementation of ISPM#15, the new study will presumably uncover current levels of compliance. The authors will use more than 73,000 new port inspection records to detect trends from 2010 through 2020, as well as the original database of about 35,000 inspections made during 2004-2009.

Bob notes that there have been significant changes in ISPM#15 since 2009. These include: a) a requirement that wood be debarked before treatment; b) approval of new treatments (dielectric heat in 2013 and sulphuryl fluoride in 2018); and c) new official definitions of “reuse,” “repair,” and “remanufacturer”.

Besides discovering overall levels of compliance, Bob and colleagues will probably select some aspects of the wood packaging pathway for specific analysis. For example, Dialogue participants want to know whether dunnage has a higher interception rate than pallets. Also, the earlier study included only wood packaging that bore the ISPM mark. This new research might compare live pest interception rates on marked versus unmarked wood.

3) A Study to Improve ISPM#15

Erin Cadwalader reported on the Entomological Society’s Grand Challenge, particularly the request from APHIS that the Society provide guidance on improving ISPM#15. This request was made in 2019; subsequent efforts to conduct a broad scoping process have been complicated and delayed by COVID-19. The goal is to determine what area of effort would lead to either 1) the highest reduction in pest incidence; or 2) the best ISPM#15 compliance.

ESA’s preliminary proposal aims to evaluate the risk associated with various types of wood packaging by analyzing data from five ports over a period of five years. Webinar participants discussed the proposal, especially trying to determine why data already collected by APHIS and CBP – specifically via Agriculture Quarantine Inspection Monitoring (AQIM) – are not adequate to support the study. Another question is whether it is useful for ESA investigators to attempt to rear insects from wood packaging rather than rely on APHIS’ identifications using molecular techniques. Erin noted that some insects – probably particularly small wood borers – might escape detection by inspectors but show up when the wood is placed in rearing chambers.

There will be further discussion of the study’s scope and methodology at the Society’s annual meeting in Autumn 2023 near Washington, D.C. (The 2022 meeting will be in Vancouver; USDA officials rarely get permission to travel to meetings outside the U.S.) ESA estimates that the study will take five years and be completed in 2028.

I am concerned that APHIS might not act on the basis of Bob Haack’s findings as soon as they are available. If they wait for completion of the ESA study, it could be at least six years from now before action is even proposed. I hope that if Haack and colleagues uncover persistent inadequacies in ISPM#15 implementation, APHIS will act unilaterally to address the problem – at least as regards the threat to the U.S. The ESA study might then become the foundation for revising the overall standard per se, that is, the entire world trading system.

Also, APHIS has already carried out a focused study of pests in wood packaging. How can their findings be incorporated into APHIS’ decisions so as to expedite action?

Wu et al. (2017) proved the efficacy of DNA identification tools and that serious pest species continued (at that time) to be present in wood packaging. Krishnankutty et al. (2020) found that 84% of interceptions occurred in wood belonging to only three families: pine, spruce, and poplar. Shipments with coniferous wood came about equally from Europe, Asia, and Mexico. Wood packaging made from poplars came primarily from China. Most of the pests in hardwood were polyphagous, and were considered to pose a higher risk. Pests in softwood samples were mostly oligophagous (feed on two or more genera in the same family). I presume that these findings prompted the studies by Mech et al. and Schulz et al.

As has been true in most studies, pest detections were often associated with shipments of heavy items, such as stone, ceramics, and terracotta; vehicles and vehicle parts; machinery, tools, and hardware; and metal. A high proportion (87%) of the wood packaging bore the ISPM15 mark, also as usual. (Data provided by CBP in past Dialogue meetings showed an even higher proportion of pest-infested wood to be marked.)

Conclusion

Clearly, programs aimed at curtaining the pest risk associated with wood packaging have not been sufficiently effective. I hope APHIS’ approval of Bob Haack’s study and agreement with the Entomological Society indicates a new willingness to understand why and take actions to fix the problems.

SOURCES

Haack, R.A., K.O. Britton, E.G. Brockerhoff, J.F. Cavey, L.J. Garrett. 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

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

Lynch, D.J. and N. Wadekar. 2021. “Africa left with fallout of US supply chain crisis”. The Washington Post. December 17, 2021.

Mongelluzzo, B. Dec 09, 2021. New long-dwell container fee bearing fruit in Oakland https://www.joc.com/port-news/terminal-operators/new-long-dwell-container-fee-bearing-fruit-oakland_20211209.html?utm_campaign=CL_JOC%20Ports%2012%2F15%2F21%20%20_PC00000_e-production_E-121985_TF_1215_0900&utm_medium=email&utm_source=Eloqua

Mongelluzzo, B. Dec. 15 2021. LA port expects imports to surge further in Q2https://www.joc.com/port-news/us-ports/la-port-expects-imports-surge-further-q2_20211215.html?utm_source=Eloqua&utm_medium=email&utm_campaign=CL_JOC%20Daily%2012/16/21_PC00000_e-production_E-122356_KB_1216_0617

Wu,Y., N.F. Trepanowski, J.J. Molongoski, P.F. Reagel, S.W. Lingafelter, H. Nadel1, S.W. Myers & A.M. Ray. 2017. Identification of wood-boring beetles (Cerambycidae and Buprestidae) intercepted in trade-associated solid wood packaging material using DNA barcoding and morphology. Scientific Reports 7:40316 

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