international trade – Center for Invasive Species Prevention

Scientists: Introduced forest pest reshaping forests, with many bad consequences … will regulators step up?

The number of introduced forest pathogens are increasing – creating a crisis that is recognized by more scientists. These experts say tree diseases are reshaping both native and planted forests around the globe. The diseases are threatening biodiversity, ecosystem services, provision of products, and related human wellbeing. Some suggest that bioinvasions might threaten forests as much as climate change, while also undermining forests’ role in carbon sequestration.

Unfortunately, I see little willingness within the plant health regulatory community to tackle improving programs to slow introductions. Even when the scientists documenting the damage work for the U.S. Department of Agriculture – usually the U.S. Forest Service — USDA policy-makers don’t act on their findings. [I tried to spur a conversation with USDA 2 years ago. So far, no response.]

counties where beech leaf disease has been detected

What the scientists say about these pests’ impacts

Andrew Gougherty (2023) – one of the researchers employed by the USDA Forest Service – says that emerging infectious tree diseases are reshaping forests around the globe. Furthermore, new diseases are likely to continue appearing in the future and threaten native and planted forests worldwide. [Full references are provided at the end of the blog.] Haoran Wu (2023/24) – a Master’s Degree student at Oxford University – agrees that arrival of previously unknown pathogens are likely to alter the structure and composition of forests worldwide. Weed, Ayers, and Hicke (2013) [academics] note that forest pests — native and introduced — are the dominant sources of disturbance to North American forests. They suggest that, globally, bioinvasions might be at least as important as climate change as threats to the sustainability of forest ecosystems. They are concerned that recurrent forest disturbances caused by pests might counteract carbon mitigation strategies.

Scientists have proclaimed these warnings for years. Five years ago, Fei et al. (2019) reported that the 15 most damaging pests introduced to the United States — cumulatively — had already caused tree mortality to exceed background levels by 5.53 teragrams of carbon per year. As these 15 pests spread and invasions intensify, they threaten 41.1% of the total live forest biomass in the 48 coterminous states. Poland et al. (2019) (again – written by USFS employees) document the damage to America’s forest ecosystems caused by the full range of invasive species, terrestrial and aquatic.

Fei et al. and Weed, Ayers, and Hicke (2013) also support the finding that old, large trees are the most important trees with regard to carbon storage. This understanding leads them to conclude that the most damaging non-native pests are the emerald ash borer, Dutch elm disease fungi, beech bark disease, and hemlock woolly adelgid. As I pointed out in earlier blogs, other large trees, e.g., American chestnut and several of the white pines, were virtually eliminated from much of their historical ranges by non-native pathogens decades ago. These same large, old, trees also maintain important aspects of biological diversity.

It is true that not all tree species are killed by any particular pest. Some tree genera or species decrease while others thrive, thus altering the species composition of the affected stands (Weed, Ayers, and Hicke). This mode of protection is being undermined by the proliferation of insects and pathogens that cumulatively attack ever more tree taxa. And while it is true that some of the carbon storage capacity lost to pest attack will be restored by compensatory growth in unaffected trees, this faster growth is delayed by as much as two or more decades after pest invasions begin (Fei et al.).

ash forest after EAB infestation; Photo by Nate Siegert, USFS

Still, despite the rapid rise of destructive tree pests and disease outbreaks, scientists cannot yet resolve critical aspects of pathogens’ ecological impacts or relationship to climate change. Gougherty notes that numerous tree diseases have been linked to climate change or are predicted to be impacted by future changes in the climate. However, various studies’ findings on the effects of changes in moisture and precipitation are contradictory. Wu reports that his study of ash decline in a forest in Oxfordshire found that climate change will have a very small positive impact on disease severity through increased pathogen virulence. Weed, Ayers, and Hicke go farther, making the general statement that despite scientists’ broad knowledge of climate effects on insect and pathogen demography, they still lack the capacity to predict pest outbreaks under climate change. As a result, responses intended to maintain ecosystem productivity under changing climates are plagued by uncertainty.

Clarifying how disease systems are likely to interact with predicted changes in specific characteristics of climate is important — because maintaining carbon storage levels is important. Quirion et al. (2021) estimate that, nation-wide, native and non-native pests have decreased carbon sequestration by live forest trees by at least 12.83 teragrams carbon per year. This equals approximately 9% of the contiguous states’ total annual forest carbon sequestration and is equivalent to the CO₂ emissions from more than 10 million passenger vehicles driven for one year. Continuing introductions of new pests, along with worsening effects of native pests associated with climate change, could cause about 30% less carbon sequestration in living trees. These impacts — combined with more frequent and severe fires and other forest disturbances — are likely to negate any efforts to improve forests’ capacity for storing carbon.

Understanding pathogens’ interaction with their hosts is intrinsically complicated. There are multiple biological and environmental factors. What’s more, each taxon adapts individually to the several environmental factors. Wu says there is no general agreement on the relative importance of the various environmental factors. The fact that most forest diseases are not detected until years after their introduction also complicates efforts to understand factors affecting infection and colonization.

The fungal-caused ash decline in Europe is a particularly alarming example of the possible extent of such delays. According to Wu, when the disease was first detected – in Poland in 1992 – it had already been present perhaps 30 years, since the 1960s. Even then, the causal agent was not isolated until 2006 – or about 40 years after introduction. The disease had already spread through about half the European continent before plant health officials could even name the organism. The pathogen’s arrival in the United Kingdom was not detected until perhaps five years after its introduction – despite the country possessing some of the world’s premier forest pathologists who by then (2012) knew what they to look for.

Clearly, improving scientific understanding of forest pathogens will be difficult. In addition, effective policy depends on understanding the social and economic drivers of trade, development, and political decisions are primary drivers of the movement of pathogens. Wu calls for collaboration of ecologists, geneticists, earth scientists, and social scientists to understand the complexity of the host-pathogen-surrounding system. Bringing about this new way of working and obtaining needed resources will take time – time that forests cannot afford.

However, Earth’s forests are under severe threat now. Preventing their collapse depends on plant health officials integrating recognition of these difficulties into their policy formulation. It is time to be realistic: develop and implement policies that reflect the true level of threat and limits of current science.

Background: Rising Numbers of Introductions

Gougherty’s analysis of rising detections of emerging tree diseases found little evidence of saturation globally – in accord with the findings of Seebens et al. (2017) regarding all taxa. Relying on data for 24 tree genera, nearly all native to the Northern Hemisphere, Gougherty found that the number of new pests attacking these tree genera are doubling on average every 11.2 years. Disease accumulation is increasing rapidly in both regions where hosts are native and where they are introduced, but more rapidly in trees’ native ranges.This finding is consistent with most new diseases arise from introductions of pathogens to naïve hosts.

Gougherty says his estimates are almost certainly underestimates for a number of reasons. Countries differ in scientific resources and their scientists’ facility with English. Scientists are more likely to notice and report high-impact pathogens and those in high-visibility locations. Where national borders are closer, e.g., in Europe, a minor pest expansion can be reported as “new” in several countries. New pathogens in North America appear to occur more slowly, possibly because the United States and Canada are very large. He suggests that another possible factor is the U.S. (I would add Canada) have adopted pest-prevention regulations that might be more effective than those in place in other regions. (See my blogs and the Fading Forest reports linked to below for my view of these measures’ effectiveness.)

Wu notes that reports of tree pathogens in Europe began rising suddenly after the 1980s. He cites the findings by Santini et al. (2012) that not only were twice as many pathogens detected in the period after 1950 than in the previous 40 years, the region of origin also changed. During the earlier period, two-thirds of the introduced pathogens came from temperate North America. After 1950, about one-third of previously unknown disease agents were from temperate North America. Another one-third was from Asia. By 2012, more than half of plant infectious diseases were caused by introduction of previously unknown pathogens.

What is to be done?

Most emerging disease agents do not have the same dramatic effects as chestnut blight in North America, ash dieback in Europe, or Jarrah dieback in Australia. Nevertheless, as Gougherty notes, their continued emergence in naïve biomes increases the likelihood of especially damaging diseases emerging and changing forest community composition.

Gougherty calls for policies intended to address both the agents being introduced through trade, etc., and those that emerge from shifts in virulence or host range of native pathogens or changing environmental conditions. In his view, stronger phytosanitary programs are not sufficient.

Wu recommends enhanced monitoring of key patterns of biodiversity and ecosystem functioning, He says these studies should focus on the net outcome of complex interactions. Wu also calls for increasing understanding of key “spillover” effects – outcomes that cannot be currently assessed but might impact the predicted outcome. He lists several examples:

the effects of drought–disease interactions on tree health in southern Europe,
interaction between host density and pathogen virulence,
reproductive performance of trees experiencing disease,
effect of secondary infections,
potential for pathogens to gain increased virulence through hybridization.
potential for breeding resistant trees to create a population buffer for saving biological diversity. Wu says his study of ash decline in Oxfordshire demonstrates that maintaining a small proportion of resistant trees could help tree population recovery.

Quirion et al. provide separate recommendations with regard to native and introduced pests. To minimize damage from the former, they call for improved forest management – tailored to the target species and the environmental context. When confronting introduced pests, however, thinning is not effective. Instead, they recommend specific steps to minimize introductions via two principal pathways, wood packaging and imports of living plants. In addition, since even the most stringent prevention and enforcement will not eliminate all risk, Quirion et al. advocate increased funding for and research into improved strategies for inspection, early detection of new outbreaks, and strategic rapid response to newly detected incursions. Finally, to reduce impacts of established pests, they recommend providing increased and more stable funding for classical biocontrol, research into technologies such as sterile-insect release and gene drive, and host resistance breeding.

Remember: reducing forest pest impacts can simultaneously serve several goals—carbon sequestration, biodiversity conservation, and perpetuating the myriad economic and societal benefits of forests. See Poland et al. and the recent IUCN report on threatened tree species.

SOURCES

Barrett, T.M. and G.C. Robertson, Editors. 2021. Disturbance and Sustainability in Forests of the Western United States. USDA Forest Service Pacific Northwest Research Station. General Technical Report PNW-GTR-992. March 2021

Clark, P.W. and A.W. D’Amato. 2021. Long-term development of transition hardwood and Pinus strobus – Quercus mixedwood forests with implications for future adaptation and mitigation potential. Forest Ecology and Management 501 (2021) 119654

Fei, S., R.S. Morin, C.M. Oswalt, and A.M. 2019. Biomass losses resulting from insect and disease invasions in United States forests. Proceedings of the National Academy of Sciences. www.pnas.org/cgi/doi/10.1073/pnas.1820601116

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

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

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.

Quirion, B.R., G.M. Domke, B.F. Walters, G.M. Lovett, J.E. Fargione, L. Greenwood, K. Serbesoff-King, J.M. Randall, and S. Fei. 2021 Insect and Disease Disturbance 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

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

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

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 https://treeimprovement.tennessee.edu/

www.fadingforests.org

Non-Native Moths in England: Ever Upward

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

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

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

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

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

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

boxtree moth; photo by Tony Morris via Flickr

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

(3) both.

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

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

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

SOURCE

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

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

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

Posted by Faith Campbell

www.fadingforests.org

Phytophthora here, Phytopthora there … level of threat is unclear

Mt. Triglav – highest peak in the Slovenian (Julian) Alps; photo by Gunter Nuyts via Pexel

Scientists have discovered sizable diversity of pathogenic Phytophthora species in Europe, specifically in the Alps of northeastern Italy and western Slovenija. They have also named a new species, and noted the need to change the definition of species previously named. See Bregant et al. – full citation at the end of this blog – open access!

Two of its findings are especially important for the US

First, the authors document the vulnerability of alpine areas to 18 Phythophthora species. Most of the plant hosts they studied have congenerics in mountainous areas of North America: Acer, Alnus, Betula, Fagus, Fragaria, Fraxinus, Ilex, Juniperus, Larix, Lonicera, Lycopodium, Pinus, Populus, Quercus, Rhododendron, Rubus, Salix, Sorbus, Taxus, and Vaccinium.

Second, the paper discusses how junipers are at particular risk. I remind you that P. austrocedrii has recently been detected in nurseries in Ohio and Oregon. This is another non-native Phythophthora that attacks junipers. I hope authorities are actively seeking to determine whether P. austrocedrii is present in nurseries or natural systems in other parts of the country.

The genus Phytophthora includes many serious plant pathogens, from the one that caused the disastrous potato blight of Ireland (Phytophthora infestans) to globally important forest-destroying invasive species, e.g., P. cinnamomi and “sudden oak death” P. ramorum.

Bregant et al. surveyed 33 small tree, shrub, and herbaceous plant species in 54 sites on the Italian island of Sardinia and the Alps of both northeastern Italy and western Slovenija. Altitudes varied from the valley bottom (700 m) to above tree line (2100 m). Sites included typical forests, riparian ecosystems, and heathlands.

The 360 isolates taken from 397 samples belonged to 17 known Phytophthora species. Some species are widespread and well-known, e.g., P. pseudosyringae. Three isolates belonged to a putative new species described by Bregant et al. – Phytophthora pseudogregata sp. nov. This total of 18 taxa was unexpectedly high. Many of the species are able to cause aerial infections via production of caducous sporangia. These can infect various organs of the plant host: fruits, leaves, shoots, twigs and branches; and cause necrosis and rots. They detected 56 new host–pathogen associations. All are listed, by type of host, in Tables 4 – 6 of the paper.

The surprising diversity and detection of taxa previously described in Australia (see below) illustrate scientists’ still poor understanding of this genus. They also confirm fears that the global phytosanitary system is unable control intercontinental movement of Phytophthora.

The authors express concern because Alpine and subalpine regions are important hotspots for floral biodiversity. The great variation in altitude, aspect, moisture regimes, etc. – including extreme conditions – results in many different habitats on small spatial scales, with large numbers of both plant species and endemics in very confined spaces. The pathogens they discovered are spreading and compromising the biodiversity of these ecologically fragile habitats.

The authors say their study emphasizes the need to assess the full diversity of Phytophthora species and the factors driving the emergence and local spread of these invasive pathogens. They specify studying the Phytophthora communities on fallen leaves to evaluate host specificity, geographic distribution and survival strategies of the main Phytophthora species detected in this study. They report that scientists are currently mapping the distribution of the new species, P. pseudogregata, in the Alpine habitats and trying to establish its natural host range.

another view of the Julian Alps; photo via Rawpixl

Bregant et al. point out that increased scientific interest over the last 30 years has led to discovery of several previously unknown Phytophthora species and pathogen-host associations. They note that all but two of the taxa in one taxonomic grouping, Sub-clade 6b, have been described in the last 12 years. The majority of taxa have been described from forest ecosystems. This trend is depicted in Figure 8 of the article. This figure also displays which species were isolated from nurseries, agricultural systems, and forest ecosystems.

Results by Plant Type – Disease incidence was highest in shrub vegetation, alpine heathlands and along the mountain riparian systems. The most impacted ecosystems were heathlands dominated by common juniper & blueberry, and riparian systems dominated by alders. In these ecosystems, the Phytophthora-caused outbreaks had reached epidemic levels trend with a high mortality rate. On shrubs and heath formations, disease was initially observed in small areas and progressively spread in a concentric manner affecting more plant species.

Hosts and Diseases – Table 3 in the article lists the 33 host plant species, briefly describes the symptoms, and in some cases provides incidence and mortality rates. Those hosts described as suffering “sudden death” included Alnus viridis, Calluna vulgaris, Genista corsica, Juniperus communis, Lycopodium clavatum, Pinus mugo,Rhododendron ferrugineum, Salix alpine, Vaccinium myrtillus and Vaccinium vitis-idaea

Role of P. pseudosyringae – The most common and widespread species detected was P. pseudosyringae. It constituted more than half of the isolates (201 of the 360). Also, it infected the highest number of hosts (25 out of 33, including all three plant types). It was isolated at 36 of the 54 sites distributed throughout all geographic regions. Seventeen of the host–pathogen associations were new to science. (See Tables 4-6, in the paper.)

*Vaccinium myrtillis* – a vulnerable host; photo by Tatyana Prozovora via Wikimedia

P. pseudosyringae dominated disease agents in the shrub community, especially among high-altitude shrubs and heaths, e.g., blueberry, dwarf pine, juniper, rhododendron, and alpine willows. Bregant et al. note that these shrubs are extremely low-growing (an adaptation to high elevation conditions). This form might favor attack by Phytophthora sporangia and zoospores present in fallen leaves. Vaccinium myrtillus suffers particularly severe disease – as previously reported in Ireland. In their laboratory studies, Bregant et al. found P. pseudosyringae to be highly aggresse on common juniper (Juniperus communis), producing wood necrosis and shoot blight only four weeks after inoculation.

The importance of P. pseudosyringae in mountainous regions has been found in previous studies in Asia, Europe, and North and South America. However, the authors call for further study of certain aspects of the species. These regard infectivity and survival of the species’ sporangia in infected tissues fallen to the ground; and the ability of oospores to persist for years in environments subject to extreme low temperatures. The former could increase the risk of outbreaks and promote faster disease progression.

The authors suggest P. pseudosyringae’s survival stems from its production of very large and thick-walled chlamydospores. This reported feature is in contradiction with the original species description, which prompts Bregant et al. to call for a correction.

Other Species, Old and New – P. cactorum was the only Phytophthora species other than P. pseudosyringae detected on all three types of hosts (small trees, shrubs, and herbaceous plants). Phytophthora plurivora was the second-most isolated species. It was detected on 12 hosts in 24 sites.

The new putative species — Phytophthora pseudogregata sp. nov. – was detected on Alnus viridis, Juniperus communis, and Rhododendron ferrugineum. As noted above, scientists are now testing whether other plant species are also hosts. It was detected at two sites in Italy — Borso del Grappa and San Nicolò di Comelico; and one site in Slovenija.

*Juniperus communis*; photo by Joan Simon via Flickr

Diseases of Juniper – Koch’s postulates have been fulfilled, demonstrating that eight Phytophthora species – the new P. pseudogregata sp. nov. as well as P. acerina, P. bilorang, P. gonapodyides, P. plurivora, P. pseudocryptogea, P. pseudosyringae, P. rosacearum – are pathogenic on common juniper (Juniperus communis). The lesions caused by P. pseudosyringae were significantly larger than those caused by other species. Lesions caused by P. pseudosyringae, P. plurivora and acerina progressively girdled the twigs causing shoot blight, browned foliage & wilting symptoms.

Most Threatening Phytophthora clades – The most-frequently isolated Phytophthora species belong mainly to clades 1 and 3 – including P. pseudosyringae. Bregant et al. say these species have several advantages for surviving in mountainous ecosystems: they produce caducous sporangia useful for aerial infections and they tolerate relatively low temperatures. Twoother species in clade 3 were isolated only from the mountains of Sardinia. One, P. psychrophila, was isolated from bleeding cankers on an oak species, Quercus pubescens. Its geographic distribution and impact are still unknown. A second species, P. ilicis, is a well-known pathogen on various hollies in Europe and North America.

Four species belonging to subclade 1a were isolated in the Alps of northeastern Italy and Slovenija. P. cactorum is a widespread polyphagous pathogen found from tropical to temperate climates. It has been responsible for severe diseases on agricultural crops and forest trees. Its occurrence in cold areas has recently been reported in Europe and Australia. The recently described P. alpina has the highest ability to survive in extremely cold conditions. It was detected on four hosts – Alnus viridis, Lonicera alpigena, Vaccinium myrtillus, and V. vitis-idaea.

Some species, e.g., P. hedraiandra and P. idaei, were reported for the first time in natural ecosystems in Europe. They have previously been linked to root and foliar disease in agricultural and ornamental nurseries.

The second-most common species in the Bregant et al. study, P. plurivora, was isolated from 54 symptomatic samples from 12 plant species; eight of the hosts are new. It is common in forest ecosystems of Central Europe – which is now considered to be its region of origin. Little is known about the closely related P. acerina. To date, the latter has been detected widely in agricultural systems, nurseries, forests, and ornamental trees in northern Italy and Sardinia. It is much more rarely found elsewhere. Both P. acerina and P. plurivora are already known to be primary pathogens involved in decline of common and grey alder in Italy.

Five of the Phytophthora species in this study, including the new species P. pseudogregata, are in Clade 6. These include pathogens very common in European forests, e.g., P. bilorbang and P. gonapodyides. Others have more limited or still unknown distributions, e.g., P. amnicola and P. rosacearum. These five species’ ability to cause aerial infections on mountain vegetation might warrant re-evaluation of the reputation of species in this clade being saprophytes or only occasional weak opportunistic pathogens.

P. pseudogregata – in sub-clade 6a – was originally described in 2011 in wet native forests in Australia and on dying alpine heathland vegetation in Tasmania. It has recently been reported in the Czech Republic and Finland. The related P. gibbosa is known to occur only in Australia, where it is associated with dying native vegetation on seasonally wet sites.

Two species of clade 8 — P. kelmanii & P. syringae — have a very limited distribution. A third – P. pseudocryptogea — is widespread in Italian ecosystems from Mediterranean areas to the tree line in the Dolomites. One species from clade 7 (P. cambivora) isolated, mainly from stem bleeding cankers of small trees and shrubs. It has two mating types; bothoccurr in the Alps of northeastern Italy and neighboring Slovenija — on Alnus incana, Laburnum alpinum and Sorbus aucuparia.

SOURCE

Bregant, C., G. Rossetto, L. Meli, N. Sasso, L. Montecchio, A. Brglez, B. Piškur, N. Ogris, L. Maddau, B.T. Linaldeddu. 2024. Diversity of Phytophthora Species Involved in New Diseases of Mountain Vegetation in Europe with the Description of Phytophthora pseudogregata sp. nov. Forests 2023, 14, 1515. https://doi.org/10.3390/f14081515 https://www.mdpi.com/journal/forests

Posted by Faith Campbell

www.fadingforests.org

A newly detected pathogen on elms

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

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

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

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

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

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

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

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

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

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

SOURCES

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

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

Posted by Faith Campbell

www.fadingforests.org

Two new Phytophthora arrivals (plus another looming) in U.S. forests & nurseries

Breeding Port-Orford cedar for resistance to Phytophthora lateralis; photo by Richard Sniezko, USDA Forest Service

At the annual meeting of the National Plant Board in July, I learned that two new Phytophthora species have been detected in the United States. Questions remain about how each arrived.

Phytophthora austrocedrii

This species was detected in a nursery in Oregon, then traced back to a supplier in Ohio. Officials are trying to determine how it entered the country – and then spread.

junipers in Great Britain killed by *P. austrocedri*; Forestry Research

In the United Kingdom, P. austrocedri has killed trees in the Juniperus and Cupressus genera. Damage is particularly significant at two sites in northern Scotland and in England’s Lake District. The principal host, Juniperus communis, is an important native species. It is already considered vulnerable. P. austrocedri has also been detected in Argentina, where it is killing the native Chilean or Patagonian cedar (Austrocedrus chilendris). The cedar species is the only one in the genus. Evidence indicates the pathogen was introduced to both Britain and Argentina; but its origin is unknown. Indeed, the species was first isolated by scientists as an unknown Phytopthora taxon on a juniper in an import/export nursery in Germany. All reported hosts are members of the Cupressaceae family (UK forest research website).

Of greater concern to Americans, P. austrocedri has also infected individual trees of Port-Orford cedar (Chamaecyparis lawsoniana). (UK forest research website).

Port-Orford cedar is a species endemic to a small range in southwestern Oregon and Northwestern California.

POC populations have been severely reduced over the past century by a different non-native Phytophthora, P. lawsonii. US Forest Service scientists recently announced that they have bred trees resistant to this pathogen – and offered seedlings for widespread planting.

Possible hosts in the Pacific Northwest – other than Port Orford cedar – include Juniperus californica, Juniperus grandis, Juniperus occidentalis, and Juniperus maritima – although the junipers might be limited to arid environments, where they would presumably be less vulnerable. https://plants.usda.gov/home/classification/15147

Research in Great Britain shows that P. austrocedri spreads in water and by movement of infected plants and contaminated soil. Footwear, camping equipment, and vehicle tires can all carry the pathogen. This makes the pathogen particularly difficult to control (this is another similarity with P. lawsonii).

Phytophthora abietivora

P. abietivora was originally found on a diseased Christmas tree (Fraser fir, Abies fraseri) in Connecticut in 2019. It has since been reported in Pennsylvania and Virginia; and in forest nurseries and Christmas tree plantations in Quebec and Ontario. The Canadians report that it has not caused disease (Canadian website). However, the Canadian representative at the National Plant Board meeting expressed concern and asked USDA APHIS to clarify what actions it is taking regarding this species.

(Natural populations of Fraser fir have been severely reduced over the past century by the balsam woolly adelgid.)

Fraser fir killed by balsam woolly adelgid; Clingman’s Dome, Great Smoky Mountains National Park

Several additional hosts have been identified, including balsam fir (Abies balsamea) and eastern hemlock (Tsuga canadensis); and deciduous or hardwood species: hickory (Carya sp.), flowering dogwood (Cornus florida), American witch hazel (Hamamelis virginiana), mountain holly (Ilex montana), red maple (Acer rubrum), silver birch (Betula lenta), American beech (Fagus grandifolia); and several oaks: white (Quercus alba), chestnut (Q. montana) and northern red oak (Q. rubra) (Canadian fact sheet).

According to the Canadian website, P. abietivora causes root rot and subsequent foliar chlorosis, discoloration, stem cankers, and sometimes tree decline and death. Determining which Phytophthora species is the causal agent of a tree’s symptoms requires laboratory testing. The Canadian fact sheet reports that wet, cool conditions provide ideal environments for P. abietivora. Like other Phytophthora species, P. abietivora can be spread through soil and water, as well as via infected plant material or pots or trays (particularly if soil remains on the equipment). The Canadian fact sheet has several photographs illustrating symptoms and additional sources.

Liriodendron tulipifera; photo by Evelyn Simak via Geograph

Phytophthora kernoviae

P. kernoviae was first detected in southwestern England in 2003. link In England, this pathogen has caused significant diseases in native Fagus sylvatica (European beech) and lesions on trunks of a European oak, Quercus robur. More worrying are the trunk lesions on the North American native yellow or tulip poplar (Liriodendron tulipifera) and lesions on foliage of Monterey pine (Pinus radiate), giant sequoia(Sequoiadendron giganteum), and several North American native shrubs, Rhododendron macrophyllum (Pacific rhododendron), R. occidentale (western rhododendron), R. catawbiense (Catawba rosebay) and Umbellularia californica (California bay laurel).

*Phytophthora kernoviae* on *R. ponticum* in Cornwall

The infestation in Cornwall is sustained by heavy sporulation on the non-native shrub Rhododendron ponticum, which is invasive in woodlands. Worrying for Americans is the fact that P. kernoviae sporulates on three plant species native to West coast forests — Rhododendron macrophyllum, R. occidentale, and Umbellularia californica – as well as on R. catawbiense, which is native to the southern Appalachians.

USDA APHIS requested adoption of a “response plan” targetting P. kernoviae under the National Plant Disease Recovery System (NPDRS). This plan was adopted in 2008 and updated in 2015.

The recovery plans found the areas at highest risk are eastern slopes of the Appalachian Mountains because this area combines a native sporulating host and residential landscaping choices that are likely to include hosts that could transport the pathogen. A lower risk was identified for West Coast forests.

Because of this status, P. kernoviae is also a “priority” pest for surveys under the Cooperative Agricultural Pest Survey (CAPS) program. According to Purdue University’s “pest tracker” website four states have reported carrying out surveys for P. kernoviae in one or more years since 2016: Oregon, Tennessee, Pennsylvania, and Virginia. Surveys in Oregon were carried out in 2018 – 2020. In 2020 the counties surveyed included Curry County, where three strains of P. ramorum link have become established. The Purdue list is not certified as accurate or complete. To date, no surveys have detected P. kernoviae in the United States or – I believe – in Canada.

SOURCES

Canadian fact sheet at https://inspection.canada.ca/en/plant-health/invasive-species/plant-diseases/p-abietivora/fact-sheet; accessed July 2024

Canadian website at https://inspection.canada.ca/en/plant-health/invasive-species/plant-diseases/p-abietivora accessed July 2024

Purdue University’s “pest tracker” website at pesttracker.org. Survey Status of Phytophthora leaf blight – Phytophthora kernoviae . (2023) accessed July 2024

UK research website at https://www.forestresearch.gov.uk/tools-and-resources/fthr/pest-and-disease-resources/phytophthora-austrocedri-disease-of-juniper-and-cypress/ accessed July 2024

For details on existence of two clonal lineages of Phytophthora austrocedrii, see Henricot, B. A. Perez-Sierra, A.C. Armstrong, P.M. Sharp, and S. Green. Phytopathology 2017. 107:12, 1532-1540.

Posted by Faith Campbell

www.fadingforests.org

Europe outlaws “ecocide”

American bullfrog (*Lithobates catesbeianus*); photo by Will Brown via Wikimedia; one of invasive animals deliberately introduced to Europe in the past

In February 2024 the European Parliament approved legislation outlawing “ecocide” and providing sanctions for environmental crimes. Member states now have two years to enshrine its provisions in national law.

The new rules update the list of environmental crimes adopted in 2008 and enhance the sanctions. The goal is to ensure more effective enforcement. Listed among the offenses are:

the import and use of mercury and fluorinated greenhouse gases,
the import of invasive species,
the illegal depletion of water resources, and
pollution caused by ships.

This action followed an in-depth analysis of the failures of the previous EU environmental directive, first adopted in 2008 (Directive 2008/99/EC). The review found that:

The Directive had little effect on the ground.
Over the 10 years since its adoption few environmental crime cases were successfully investigated and sentenced.
Sanction levels were too low to dissuade violations.
There had been little systematic cross-border cooperation.

EU Member states were not enforcing the Directive’s provisions. They had provided insufficient resources to the task. They had not developed the needed specialized knowledge and public awareness. They were not sharing information or coordinating either among individual governments’ several agencies or with neighboring countries.

The review found that poor data hampered attempts by both the EU body and national policy-makers to evaluate the Directive’s efficacy.

The new Directive attempts to address these weaknesses. To me, the most important change is that complying with a permit no longer frees a company or its leadership from criminal liability. These individuals now have a “duty of care”. According to Antonius Manders, Dutch MEP from the Group of the European People’s Party (Christian Democrats), if new information shows that actions conducted under the permit are “causing irreversible damage to health and nature – you will have to stop.” This action reverses the previous EU environmental crime directive – and most member state laws. Until now, environmental crime could be punished only if it is unlawful; as long as an enterprise was complying with a permit, its actions would not be considered unlawful. Michael Faure, a professor of comparative and international environmental law at Maastricht University, calls this change revolutionary.

Another step was to make corporate leadership personally liable to penalties, including imprisonment. If a company’s actions cause substantial environmental harm, the CEOs and board members can face prison sentences of up to eight years. If the environmental harm results in the death of any person, the penalty can be increased to ten years.

Financial penalties were also raised. Each Member state sets the fines within certain parameters. Fines may be based on either a proportion of annual worldwide turnover (3 to 5%) or set at a fixed fine (up to 40 million euros). Companies might also be obliged to reinstate the damaged environment or compensate for the damage caused. Companies might also lose their licenses or access to public funding, or even be forced to close.

Proponents of making ecocide the fifth international crime at the International Criminal Court argue that the updated directive effectively criminalizes “ecocide” — defined as “unlawful or wanton acts committed with knowledge that there is a substantial likelihood of severe and either widespread or long-term damage to the environment being caused by those acts.”

Individual member states also decide whether the directive will apply to offences committed outside EU borders by EU companies.

Some members of the European Parliament advocate for an even stronger stance: creation of a public prosecutor at the European Union level. They hope that the Council of Europe will incorporate this idea during its ongoing revision of the Convention on the Protection of the Environment through Criminal Law. To me, this seems unlikely since the current text of the Convention, adopted by the Council in 1998, has never been ratified so it has not come into force.

The Council of Europe covers a wider geographic area than the European Union – 46 member states compared to 27. Members of the Council of Europe which are not in the EU include the United Kingdom, Norway, Switzerland, Bosnia-Hercegovina, Serbia, Kosovo, Albania; several mini-states, e.g., Monaco and San Remo; and countries in arguably neighboring regions, e.g., Armenia, Azerbaijan, Georgia, and Turkey.

While I rejoice that invasive species are included in the new Directive, I confess that I am uncertain about the extent to which this inclusion will advance efforts to prevent spread. The species under consideration would apparently have to be identified by some European body as “invasive” and its importation restricted. As we know, many of the most damaging species are not recognized as invasive before their introduction to a naïve environment. On the other side, the requirement that companies recognize new information and halt damaging actions – even when complying with a permit! – provides for needed flexibility.

Posted by Faith Campbell

www.fadingforests.org

Read both: a short call to action (41 pp) based on a long report (952 pp!) Then Act!!!

U.S. Department of Agriculture headquarters; lets lobby these people! photo by Wikimedia

Twenty-three scientists based around the world published a Letter to the Editor titled “Overwhelming evidence galvanizes a global consensus on the need for action against Invasive Alien Species” It appears in the most recent edition of Biological Invasions (2024) 26:621–626.

The authors’ purpose is to draw attention to the release of a new assessment by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services’ (IPBES).

The report was issued in September 2023. It is described as the most comprehensive global synthesis of the current knowledge on the bioinvasion process and the impacts of invasive alien species (952 pages!). Its preparation took nearly a decade. Most important, it represents the first consensus among governments and scientists worldwide on the magnitude and extent of the threats that bioinvasions pose to nature, people, and the economy.

The proposed solutions are astoundingly broad and ambitious: transformation of how governments and societies perform. I don’t disagree! However, we need interim steps – “bites of the elephant.” In my view, the report falls short on providing these.

Our challenge: join others in bringing this analysis to decision-makers’ attention. Can we pull out information that will help persuade U.S. decision-makers – governmental and non-governmental – that the threat is both urgent and solvable? How do we more effectively advocate for the aggressive, science-based action that we all know is needed?

(I hope that the fact that the report was prepared under the auspices of the Convention on Biodiversity, to which the U.S. is not a party, does not intensify the challenge for us.)

Why we need to restructure the behavior of governments and societies

Bioinvasions are facilitated by policies, decision-making structures, institutions, and technologies that are almost always focused on achieving other goals. Species transport and introduction are driven by policies aimed at promoting economic growth – especially trade. Later stages of invasions, i.e., establishment and some spread, are accelerated by certain uses of land and sea plus climate change. For example, activities that fragment habitats or cause widespread habitat disturbance provide ready places for bioinvasions. Rarely are those who gain by such policies held accountable for the harms they produce via bioinvasions.

To address these unintended consequences, the IPBES report calls for “integrated governance.” Its authors want coordination of all policies and agencies that touch on the indirect drivers, e.g., conservation; trade; economic development; transport; and human, animal, and plant health. Policy instruments need to reinforce – rather than conflict with — strategic invasive species management across sectors and scales. This involves international agreements, national regulations, all governmental sectors, as well as industry, the scientific community, and ordinary people – including local communities and Indigenous Peoples.

The report also calls for establishment of open and inter-operable information systems. This improved access to information is critical for setting priorities; evaluating and improving regulations’ effectiveness; and reducing costs by avoiding duplication of efforts.

Critically important information that is often unspoken:

Indirect causes underlying the usual list of human activities that directly promote bioinvasions are the rapid rise of human population and even more rapid rise in consumption and global trade.
Biosecurity measures at international borders have not kept pace with the growing volume, diversity, and geographic origins of goods in trade.

Continuation of current patterns is expected to result in one-third more invasive species globally by 2050. However, this is an underestimate because today’s harms reflect the consequences of past actions – often from decades ago. Drivers of invasions are expected to grow in both volume and impact.
We can prevent and control invasive alien species – but that success depends on the availability of adequate, sustained resources, plus capacity building; scientific cooperation and transfer of technology; appropriate biosecurity legislation and enforcement; and engaging the full range of stakeholders. These require political will.
A major impact of bioinvasion is increased biotic homogenization (loss of biological communities’ uniqueness). This concerns us because we are losing the biotic heterogeneity that provides insurance for the maintenance of ecosystem functioning in the face of ongoing global change.
The IPBES study asserts that successfully addressing bioinvasions can also strengthen the effectiveness of policies designed to respond to other drivers, especially programs addressing conservation of biological diversity, ensuring food security, sustaining economic growth, and slowing climate change. All these challenges interact. The authors affirm that evidence-based policy planning can reflect the interconnectedness of the drivers so that efforts to solve one problem do not exacerbate the magnitude of others and might even have multiple benefits.

More Key Findings

Overall, 9% (3,500) of an estimated 37,000 alien species established in novel environments are invasive (those for which scientists have evidence of negative impacts). Proportions of invasives is high among many taxonomic groups: 22% of all 1,852 alien invertebrates; 14% of all 461 alien vertebrates; 11% of all 141 alien microbes; and 6% of all 1,061 alien plants. (The discussion of probable undercounts relates to aquatic systems and certain geographic regions. However, I believe these data are all undermined by gaps in studies.)
Invasive alien species – solely or in combination with other drivers – have contributed to 60% of recorded global extinctions. Invasive species are the only driver in 16% of global animal and plant extinctions. Some invasive species have broader impacts, affecting not just individual species but also communities or whole ecosystems. Sometimes these create complexoutcomes that push the system across a threshold beyond which ecosystem restoration is not possible. (No tree pests are listed among the examples.)

dead whitebark pine in Glacier National Park; photo by National Park Service

The benefits that some non-native – even invasive – species provide to some groups of people do not mitigate or undo their negative impacts broadly, including to the global commons. The report authors note that beneficiaries usually differ from those people or sectors that bear the costs. The authors cite many resulting inequities.
There are insufficient studies of, or data from, aquatic systems, and from Africa; Latin America and the Caribbean; and parts of Asia.
The number of alien species is rising globally at unprecedented and increasing rates. There are insufficient data specifically on invasive species, but they, too, are thought to be rising at similar rates.
Horticulure is a major pathway for introducing 46% of invasive alien plant species worldwide.
Regarding invasive species’ greater impact on islands,the IPBES report mentions brown tree snakes on Guam and black rats on the Galapagos Islands. It also notes that on more than a quarter of the world’s islands, the number of alien plants exceeds the total number of native ones. See my blogs on non-native plants on Hawai`i and Puerto Rico. In addition, I have posted several blogs regarding disease threats to rare bird species in Hawai`. The IPBES report does not mention these.

Where the Report Is Weak: Interim Steps

The report endorses adoption of regulated species (“black”) lists.
The report emphasizes risk analysis of species. Unfortunately IPBES’ analysis was completed before publication of the critique of risk analysis methods by Raffa et al. ( (2023) (see references). However, we must take the latter into consideration when deciding what to advocate as U.S. policy.
The report authors call for more countries to adopt national legislation or regulations specifically on preventing and controlling invasive species. (They note that 83% of countries lack such policies). They also list the many international agreements that touch on invasive species-relevant issues. However, Raffa et al. found that the number of such agreements to which a country is a party bears no relationship to the numbers of alien species detected at its border or established on its territory.
The challenge to risk assessment posed by multiple sources of uncertainty can be managed by recognizing, quantifying, and documenting the extent of that uncertainty.

Beech leaf disease – one of many non-native pests that were unknown before introduction to a naive ecosystem. Photo by Jennifer Koch, USDA Forest Service

I appreciate the report’s emphasis on the importance of public awareness and engagement, but I thought the discussion of effective campaigns lacked original ideas.

The report did not fulfill its own goal of fully exploring unappreciated impacts of policies in its discussion of habitat fragmentation. For example, the report notes that grazing by feral alien ungulates facilitates the spread of invasive alien plant species. However, it does not mention the similar impact by livestock grazing (Molvar, et al. 2024).

SOURCES

Molvar, E.M., R. Rosentreter, D. Mansfield, and G.M. Anderson. 2024. Cheat invasions: History, causes, consequences, and solutions. Hailey, Idaho: Western Watersheds Project, 128 pp.

Raffa, K.F., E.G. Brockerhoff, J-C. GRÉGOIRE, R.C. Hamelin, A.M. Liebhold, A. Santini, R.C. Venette, and M.J. Wingfield. 2023. Approaches to forecasting damage by invasive forest insects and pathogens: a cross-assessment. BioScience 85 Vol. 73 No. 2 (February 2023) https://academic.oup.com/bioscience

Posted by Faith Campbell

www.fadingforests.org

Container numbers, origins, routes & destinations change — as do pest risks

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

Import Volumes in 2023

U.S. imports in 2023 fell about 13% from 2022 levels, returning to approximate pre-pandemic 2019 levels (Mongelluzzo 2024). The 2023 total was 24.2 million TEUs, (a united equal to twenty-foot container) compared to nearly 28 million TEUs in the previous two years (JoC.com February 2024). Imports from Asia in 2023 totalled 16.2 million TEUs. This was above the 2019 level (15.9 million TEUs) but below the more than 18.5 million TEUs in 2022 and 2021 (Mongelluzzo 2024).

This decline in imports from Asia reflected trends in the first months of 2023. This trend reversed sharply in October; during that month, containerized imports were 12.4% higher than in October 2022, even 1.1% higher than in pre-COVID October 2019 (Mongelluzzo, 2023). The upward trend continued through November: U.S. imports from Asia that month were 10.8% higher than the same month in 2022 (Journal of Commerce).

New Shipping Routes = More Possible Pests

chir pine (*Pinus roxburghii*) – a 5-needle pine native to the Himalaya in India; photo by Treesftf via Flickr

Proposed new shipping routes will expand the range of pests that can be introduced to eastern ports. For example, in November 2023, the Indian company Ocean Network Express announced plans to begin direct shipments from India to the Ports of New York-New Jersey, Savannah, Jacksonville, Charleston, and Norfolk. Expected cargo includes electronics, apparel, textiles, and foods. (Angell, 2023a) Have USDA authorities evaluated what pest species might be introduced from India?

Traders also expect rising trade volumes from South America in response to shifts in supply chains. Industries include textiles, pharmaceuticals, renewable energy, information technology, and agriculture.

The U.S. is importing more chilled produce from the west coast of South America to meet demand when these fruits are out-of-season in the U.S. The number of refrigerated containers rose to 395,572 TEUs (equivalents of twenty-foot containers). (Knowles. 2023) The Port of Savannah is actively courting these imports; it can now handle more than 3,000 refrigerated containers at one time and is expanding its capacity (Griffis 2023). Chile has a Mediterranean climate similar to that of California; Dr. Mark Hoddle reports several pests of avocado are found in neighboring Peru.

blueberries in Chile; Jardin Botanico Nacional, Chile via Flickr

Problems in the canals likely to push trade from Asia back to California ports

In an editorial published on January 25, 2024, The Washington Post reports that drought has caused water levels in the Panama Canal to fall below what is needed to operate the locks. In normal years, about 5% of global maritime trade passes through the canal. This includes nearly half the containers shipped from northeast Asia to the eastern United States. The reduction in numbers of ships moving through the Canal has affected supply chains in agriculture and energy. The situation is further complicated by wars in the Middle East hampering shipments through the Suez Canal.

The Post describes the Panamanian government’s efforts to buttress the canal, which is a major source of income. Droughts elsewhere are also impeding transport, e.g., the Amazon, Rhine, and Mississippi rivers. In the Post’s view, “threats to global growth will make it harder to … respond to poverty and hunger. … Ultimately, prevention, by arresting the emission of planet-warming greenhouse gases, is the only way to stop the list of looming climate-related threats to the global economy from getting even longer.”

Here, my focus is on what this means for volumes of ships and containers visiting ports in the eastern United States – and the associated risks of pest introductions.

Ambitious Plan for Eastern Ports

As I have pointed out in previous blogs [on the website home page, scroll below the “Archives” to “Categories”, click on “wood packaging”, especially this one], ports in eastern and Gulf Coast states have been eagerly conducting dredging operations and making other preparations to attract large container ships bringing goods from Asia. As of just a few months ago, several ports had ambitious plans. The Port of Virginia will reach a depth of 55 feet this year (Angell, 2023b). The Port of Charleston already has a 52-foot depth. Nevertheless, the port authority hopes to further deepen the channel so that it can quintuple its capacity over a decade — from 500,000 TEUs to 2.5 million TEUs (Anonymous, 2024). The Port of New York-New Jersey has approved $19 million to study deepening the ship channels from 50 to 55 feet. The Port Authority hopes to persuade Congress to share the costs (Angell, 2023b). None of the reporting mentions any consideration of the possible pest risk despite past disasters – e.g., introduction of the redbay ambrosia beetle to Savannah or Asian longhorned beetle to Charleston.

redbay mortality in Claxton, GA; photo by Scott Cameron

The proportion of total U.S. imports going to West Coast ports in 2023 was 53.6% (Mongelluzzo, 2023). Journal of Commerce’ long-time analyst Bill Mongelluzzo expects the effective closure of both the Suez (attacks on shipping) and Panama canals will push more imports from Asia to the Ports of Los Angeles and Long Beach. These linked ports now handle 32% of all U.S. imports. Mongelluzzo expects the increased volume to create new congestion problems (Mongelluzzo 2024).

containers at Long Beach in early 2000s; photo courtesy of Port of Long Beach

SOURCES

Angell, M. 2023a. ONE readies Indian-U.S. East Cost service as part of 2024 network rollout. Journal of Commerce. November 27, 2023.

Angell, M.2023b. NY-NJ port takes next steps to study dredging amid larger ship calls. Journal of Commerce December 20, 2023. https://www.joc.com/article/ny-nj-port-takes-next-steps-study-dredging-amid-larger-ship-calls_20231220.html?utm_source=Eloqua&utm_medium=email&utm_campaign=CL_JOC%20Daily%2012%2F21%2F23%20Non-Subscriber_PC00000_e-production_E-165003_DS_1221_0617

AnonymoU.S.. SC Ports requests study to deepen channel leading to North Charleston Terminal. Journal of Commerce Daily Newswire. January 12, 2024

Griffis, T.E. 2023. New ZIM service takes advantage of Savannah’s expanding cold storage network. Journal of Commerce. September 22, 2023.

Hoddle. M.S. 2023. A new paradigm: proactive biological control of invasive insect pests. BioControl https://doi.org/10.1007/s10526-023-10206-5

Knowles, G. 2023. Sourcing shift caU.S.es surge in South American logistics investment. Journal of Commerce. September 25, 2023.

Mongelluzzo, B. 2023. U.S. imports from Asia hit 2023 high in October despite muted peak season. Journal of Commerce.

Mongelluzzo, B. 2024. U.S. imports from Asia fell near pre-COVID levels in 2023, but uncertain ’24 awaits. Journal of Commerce. January 19, 2024.

Imports from Asia rise; perhaps 2,000 or more containers carrying insect pests enter U.S. in one month

Wood packaging – crates, pallets, spools for wire, etc. — has been recognized as a major pathway for introduction of tree-killing pests since the Asian longhorned beetle was detected in New York and Chicago in the late 1990s. As of 2021, 65 new species of non-native wood- or bark-boring Scolytinae had been detected in the United States (Rabaglia; full citation at end of the blog).

As I have often reported [To see my 40+ earlier blogs about wood packaging material, scroll down below archives to “Categories,” click on “wood packaging”.], the international phytosanitary community adopted the International Standard for Phytosanitary Measures (ISPM) #15. The goal of ISPM#15 is to “significantly reduce” [not eliminate] the risk of pests associated with solid wood used for constructing packaging (e.g., crates, pallets), from being introduced to other countries through international trade.

I recently reviewed the first 20+ years of implementation of ISPM#15 including two analyses by Robert Haack and colleagues in a blog in December 2022. I have also provided the broader context of the World Trade Organization (WTO) in my Fading Forests II report.

I last blogged about U.S. import volumes in June. My silence since reflected the significant decline in U.S. imports from Asia. This reduction had reduced the likelihood that a new tree-killing pest would be introduced from that region – or that an already-established pest would be introduced to a U.S. region that had escaped it so far.

However, U.S. imports from Asia have suddenly grown! In October 2023, containerized imports from Asia were 12.4% higher than a year ago – and 6% higher than in September. According to the Journal of Commerce (full citation at end of blog), U.S. retailers anticipate consumers will purchase lots of gifts for the upcoming Christmas season.

The U.S. imported 1.57 million TEU from Asia in October. This volume exceeded even the pre-COVID levels. How great is the associated risk of a pest introduction? To calculate that, I apply the following:

most U.S. imports arrive in 40-foot-long containers, so divide TEU by 2 = 785,000
a decade-old estimate that 75% of containers in maritime shipments contain wood packaging (Meissner et al.) = 588,750 containers with wood packaging (I suspect it is more).
the estimate by Haack et al. 2014 that 0.1% (1/10^th of 1 percent) of consignments (which usually means a single container) harbor tree-killing pests;
the estimate by Haack et al. 2022 that 0.22% of consignments harbor tree-killing pests.

The result of these calculations is an estimate of 648 containers (using the 2009 global estimate), or 1,727 containers (using the 2022 global estimate), or 5,730 containers (using the 2010-2020 estimate for China specifically) entering the country in one month harbored tree-killing pests. Since West Coast ports received 54% of those containers, the estimated number of containers transporting pests that enter California, Washington, or Oregon ranged from 349 to 3,042. The rest are scattered among the dozens of ports on the East and Gulf coasts.

With drought limiting container ship transits through the Panama Canal (Szakonyi 2023), the threat to East and Gulf coast ports might not rise commensurately.

Because of the low levels of imports in previous months, U.S. imports from Asia remain significantly below levels in previous years: 16.6% lower for the January – September period compared to 2022.

The 2022 analysis found that the rate of wood packaging from China that is infested has remained relatively steady since 2003: 1.26% during 2003–2004, and ranged from 0.58 to 1.11% during the next three time periods analyzed. Packaging from China made up 4.6% of all shipments inspected, but 22% of the 180 consignments with infested wood packaging. Thus the proportion of Chinese consignments with infested wood is five times greater than would be expected based on their proportion of imports. Note the great impact of this high infestation rate on the number of containers transporting tree-killing pests to the U.S. in the paragraph above: more than 8,000 containers compared to about 2,000.

I remind you that the U.S. and Canada have required treatment of wood packaging from China since December 1998. Why are the responsible agencies in the United States not taking action to correct this problem? [which has persisted for 2 decades]

The fact is – as I have argued numerous times — a pallet or crate bearing the ISPM#15 mark has not proved to be a reliable indicator as to whether the wood is pest-free. (This might be because the wood had not been treated, or if it was, the treatment failed). All the pests detected in the Haack et al. studies (after 2006) were in wood packaging bearing the ISPM#15 mark. As noted in my past blogs [click on the “wood packaging” category to bring up blogs about wood packaging and enforcement], Customs and Border Protection also report that nearly all the wood packaging in which that they detected insect pests bore the ISPM#15 mark.

According to Angell in November (full citation at end of blog), U.S. imports from India to the east coast fell by 15% in the first 10 months of 2023 compared to last year – to a total of 623,356 TEUs. This might change in the future: a shipper has promised to start weekly arrivals from India beginning in May 2024. the company plans calls at New York-New Jersey, Savannah, Jacksonville, Charleston, and Norfolk. The ships will call, en route, at ports in Saudi Arabia, Egypt, and Spain. What pests might be hitching a ride on these shipments?

SOURCES

Haack RA, Britton KO, Brockerhoff EG, Cavey JF, Garrett LJ, 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

Haack RA, Hardin JA, Caton BP and Petrice TR. 2022. Wood borer detection rates on wood packaging materials entering the United States during different phases of ISPM#15 implementation and regulatory changes. Frontiers in Forests and Global Change 5:1069117. doi: 10.3389/ffgc.2022.1069117

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.

Mongelluzzo, B. 2023. U.S. imports from Asia hit 2023 high in October despite muted peak season. Journal of Commerce https://www.joc.com/article/us-imports-asia-hit-2023-high-october-despite-muted-peak-season_20231116.html (access limited to subscribers, unfortunately)

Angell, M. 2023. ONE readies India-US East Coast service as part of 2024 network rollout. Journal of Commerce. November 27, 2023

Rabaglia, R. 2021. The increasing number of non-native bark and ambrosia beetles in North America. International Union of Forest Research Organizations. Prague, Czech Republic. September 2021

Szakonyi, M. 2023. Carriers Weigh Options as Panama Canal restrictions become fact of life. Journal of Commerce. November 21, 2023. (Access limited to subscribers, unfortunately)

Posted by Faith Campbell

www.fadingforests.org

International Phytosanitary System: More Evidence of Failure

Rome: home of the International Plant Protection Convention

I often assert that the international phytosanitary system has proven to be a failure in preventing introductions.

Some of the recent publications support my conclusion – although most don’t say so explicitly. For example, the Fenn-Moltu et al. (2023) study of insect transport and establishment around the world found that the number of invasive species-related treaties, regulations and legislation a country has adopted had no significant effect on either the number of insect species detected at that country’s border or the number of insect species that established in that country’s ecosystems..

Weber et al. also found considerable evidence that international and U.S. phytosanitary systems are not curtailing introduction of insects and entomophagic pathogens. In my earlier blog I review their study of unintentional “self-introductions” of natural enemies of arthropod pests and invasive plants. They conclude that these “self-introductions” might exceed the number of species introduced intentionally. These introductions have been facilitated by the usual factors: the general surge in international trade; lack of surveillance for species that are not associated with live plants or animals; inability to detect or intercept microorganisms; huge invasive host populations that allow rapid establishment of their accidentally introduced natural enemies; and lack of aggressive screening for pests already established. Examples cited include species introduced to the United States’ mainland and Hawai`i specifically.

The U.S. Capitol – one of the entities that can reflect **our** priorities in setting phytosanitary policy

As I point out often, altering human activities that facilitate invasion is a political process. So is amending international agreements that are not effective. We need to determine the cause of the failures of the existing institutions and act to rectify them. See my critiques of both the American and international phytosanitary system Fading Forests II and Fading Forests III (see links at the end of this blog) and my earlier blogs, especially this and this.

SOURCES

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

Weber, D.C., A.E. Hajek, K.A. Hoelmer, U. Schaffner, P.G. Mason, R. Stouthamer, E.J. Talamas, M. Buffington, M.S. Hoddle and T. Haye. 2020. Unintentional Biological Control. Chapter for USDA Agriculture ResearchService. Invasive Insect biocontrol and Behavior Laboratory. https://www.ars.usda.gov/research/publications/?seqNo115=362852

Posted by Faith Campbell