Protea repens and fynbos vegetation near Table Mountain; photo by Mike Wingfield
South Africa is a country of immense biological diversity. It is also one that recognizes the threat invasive species pose to its natural wealth – and to the economy and livelihoods of ordinary people.
Also, South Africans are trying hard to improve the country’s invasive species program. It recently released the second national report assessing how well it is curtailing introductions and minimizing damage. As I describe in a companion blog, I find these reports to contain exceptionally thorough and honest appraisals of South Africa’s invasive species programs. I address that value in the companion blog, where I compare the South African report — and its findings — to U.S. government reports on our invasive species programs.
In South Africa, bioinvasion ranks third – after cultivation and land degradation – as a threat to the country’s impressive biodiversity. Invasive species are responsible for 25% of all biodiversity loss. Certain taxa are at particular risk: native amphibians and freshwater fishes, and some species of plants and butterflies.
Particularly disturbing is the bioinvasion threat to the Fynbos biome. The report notes that 251 non-native species have been identified in this system. This finding causes concern because the Fynbos is a unique floral biome. In fact, it constitutes the principal component of one of only six floral kingdoms found on Earth: the Cape Floral Kingdom (or region). For more information, go here.
map of South Africa showing fynbos biome
Not surprisingly, invasive bird and plant species are most numerous around major urban centers. The report concludes that this is probably because most non-native birds are commensal with humans; most birds and plants were first introduced to urban centers; and there is greater sampling effort there. Indeed, the patterns of (detected) invasive plant richness are still highly sensitive to sampling effort.
South Africa is considered a leader on invasive species management. However, its record is spotty.
Successes
Biocontrol interventions are considered a success. South Africa has approved release of 157 biocontrol agents, including seven since 2016. All the recent agents (and probably most others) target invasive plants. The South African biocontrol community conducts a comprehensive review of their effectiveness at roughly 10-year intervals. The fourth assessment is currently under way. Also, the report considers eradication of non-native fish (primarily sport species) from several wetlands and river reaches to have been successful. (However, opposition by sport fishermen has delayed listing of some trout species as invasive.)
Failures
On the other hand, strategies to combat invasive plants, other than by biocontrol, appear to be having little success. Even the extent of plant invasions in national parks is poorly documented. Also, the report highlights ballast water as an inadequately managed pathway of invasion.
The report estimates that three new non-native species arrive in South Africa accidentally or illegally every year. Interestingly, reported species arrivals have declined in the current decade compared to the preceding one. The report’s authors consider this to probably be an underestimate caused by the well-known lag in detecting and reporting introductions. The apparent decline also is contrary to global findings. Table 1 in Seebens et al. 2020 (full citation at end of blog) projected that the African continent would receive approximately 767 new alien species between 2005 and 2050.
Even the introductory pathways are poorly known: the pathway for 54% of the taxa introduced to South Africa are unknown. Of the species for which the introductory pathway is known, horticultural or ornamental introductions of plants dominate – 15% of that total. A second important pathway – for accidental introductions – is shipping (5% of all introductions). Other pathways thought to be prominent during 2017–2019 are the timber trade, contaminants on imported animals, and natural dispersal from other African countries where they had previously been introduced.
PSHB symptoms on Vachellia sieberiana; photo by Trudy Paap
Polyphagous shothole borer
The report highlights as an example of a recent introduction that of the polyphagous shothole borer (PSHB, Euwallacea fornicatus). https://www.dontmovefirewood.org/pest_pathogen/polyphagous-shot-hole-borer-html/http://nivemnic.us/south-africas-unique-flora-put-at-risk-by-polyphagous-shot-hole-borer/ See Box 3.1 in the report. This species is expected to have huge impacts, especially in urban areas. While most of the trees affected so far are non-native (e.g., maples, planes, oaks, avocadoes), several native trees are also reproductive hosts. https://www.fabinet.up.ac.za/pshb In response to the introduction, the government established an interdepartmental steering committee, which has developed a consolidated strategy and action plan. However, as of October 2020 the shot hole borer had not been listed under invasive species regulations, even on an emergency basis. It had been listed as a quarantine pest of agricultural plants (e.g., avocado) per the Agricultural Pests Act 1983.
As note in my blog assessing the report, the report bravely concludes that the government’s regulatory regime is only partially successful (whereas three years ago it graded it as “substantial”). The downgrade is the result of a more thorough evaluation of the regulatory regime’s effectiveness.
SOURCES
SANBI and CIB 2020. The status of bioinvasions and their management in South Africa in 2019. pp.71. South African National BD Institute, Kirstenbosch and DSI-NRF Centre of Excellence for Invasion Biology, Stellenbosch. http://dx.doi.org/10.5281/zenodo.3947613
Seebens, H., S. Bacher, T.M. Blackburn, C. Capinha, W. Dawson, S. Dullinger, P. Genovesi, P.E. Hulme, M. van Kleunen, I. Kühn, J.M. Jeschke, B. Lenzner, A.M. Liebhold, Z. Pattison, J. Perg, P. Pyšek, M. Winter, F. Essl. 2020. Projecting the continental accumulation of alien species through to 2050. Global Change Biology. 2020;00:1 -13 https://onlinelibrary.wiley.com/doi/10.1111/gcb.15333
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
The emerald ash borer (EAB) was first detected in European Russia in 2003, in Moscow. By 2020, EAB was recorded in 16 provinces [=‘oblast’] of European Russia, especially to the West of Moscow towards the borders with Belarus and Ukraine.
Russian scientists have documented that the emerald ash borer is spreading faster in the southwest of the country and in neighboring Ukraine than in the northwest (near St. Petersburg and the Baltic countries).
Despite an abundance of ash [both green ash (Fraxinus pennsylvanica) – native to North America – and European ash F. excelsior], EAB population density in the northwest remains low and damage is in scattered clusters.
However, in September 2020 officials detected an isolated outbreak in a St. Petersburg suburb, 520 km away from the apparent edge of the principal Russian population. The authors believe this outbreak has been present since 2015. They think it is the result of transport of EAB either by “insect-hitchhiking” on vehicles or by movement of plants for planting or other commodities.
The Petersburg population is only 130 km from Estonia and Finland – the border with the European Union.
A thousand kilometers to the south, in southwest Russian eastern Ukraine, an outbreak was reported in June 2019. By the next summer, EAB were detected more than 100 km to the West. While this outbreak is still 800 km from Ukraine’s border with eastern Europe (Poland, Slovakia, Hungary, Romania), the authors note that rapid spread is likely since F. excelsior and F. pennsylvanica have been extensively planted along roads, railways, field shelter belts, and urban greenings.
The slower spread in the North is attributed to colder temperatures, the local abundance of food, and possibly pressure by the native parasitoid Spathius polonicus Niezabitowski (note that USDA APHIS has approved two Spathius species as biocontrol agents in the U.S.). On the other hand, the climate is milder in Saint Petersburg (along the coast) than it is inland; and ash woodlands are common along the Baltic coast.
Noting that ash dieback (Hymenoscyphus fraxineus) has devastated more than 95% of European ash populations, the authors express concern about the future of ash.
SOURCE
Musolin, D.L.; Selikhovkin, A.V.; Peregudova, E.Y.; Popovichev, B.G.; Mandelshtam, M.Y.; Baranchikov, Y.N.; Vasaitis, R. North-Westward Expansion of the Invasive Range of Emerald Ash Borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) towards the EU: From Moscow to Saint Petersburg. Forests 2021, 12, 502. https://doi.org/10.3390/f12040502
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
myrtle rust infestation; source: New Zealand Department of Agriculture alert May 2017
Pacific countries’ policy and management responses to the spread of the myrtle rust pathogen, Austropuccinia psidii (formerly Puccinia psidii), has had puzzling – even infuriating – gaps … which perhaps have contributed to its spread and damage.
Reminder: ‘ōhi‘a or myrtle rust attacks species in the Myrtaceae – a family now said to include 5,600 species (Stewart et al. 2018). Ten percent of Australia’s native flora is in the family – or about 1,300 species. New Zealand is home to 27 native plants in the Myrtaceae family (Bereford et al. 2019) and the Hawaiian Islands to eight (JB Friday pers. comm.). See a writeup about the disease here.
Austropuccinia psidii is one of the global invaders: it has invaded 27 countries on several continents. It is apparently native to parts of the American tropics.
Levels of worry rose considerably with the pathogen’s spread across the Pacific beginning with the detection in Hawai‘i in spring 2005. Additional introductions in the region were Japan in 2009; China in 2011; Australia, New Caledonia, and South Africa in 2013; and New Zealand in 2017.
The known host range currently exceeds 500 species in 86 genera – all in the Myrtaceae family. The pathogen has several strains or biotypes; the impact of the various biotypes on the various host species differs. Environmental factors also apparently affect disease.
[For my earlier discussions of threats to the unique Hawaiian flora, go here for dryland flora, here and here for more general discussions. I discuss National Park Service efforts – including in Hawai`i – here.]
There are several factors that militate against a political entity choosing to act:
1) Inherent Difficulty in Controlling Wind-Borne pathogen
In both Hawai`i and Australia, the rust spread rapidly once it was established outside of nurseries. In Hawai`i, it had spread to all the islands within a few months of its detection in spring 2005 (Loope and La Rosa 2008). In Australia, the rust was established in natural ecosystems throughout coastal New South Wales and to far northern Queensland by mid-2012 – less than two years after detection (Carnegie et al. 2016). The number of host species also expanded rapidly – from 214 native plants in 2016 (Carnegie et al. 2016) to 393 species by 2019 (Winzer et al. 2019). Myrtle rust is believed to have been carried to Australia and New Caledonia on imported plants or cut vegetation; then to New Zealand by winds from Australia across the Tasman Sea (Toome-Heller et al. 2020).
2) Lack of Clarity About Probable Impacts
Austropuccinia psidiihad been introduced fairly widely before 2000, and some biotypes had caused significant damage on introduced species within both the native and introduced ranges of the rust – e.g., Eucalyptus in Brazil, allspice (Pimento doica) in Jamaica, rose apple (Syzygium jambos) in Hawai`i. However, the rust had had little impact on native floras in introduced ranges, especially not on widespread species (Carnegie et al. 2016).
However, concerns existed in the Pacific region because of:
Its wide host range (before the introduction to Australia, the known host range was “only” 129 species in 33 genera Carnegie et al. 2016).
The severe damage to Australian genera growing outside their native range, e.g., nurseries and plantations of Eucalyptus in South America and Melaleuca quinquenervia and Rhodomyrtus tomentosa in Florida (Carnegie et al. 2016)
In Hawai`i, ‘ōhi‘a rust caused little damage to the dominant tree species in Hawaiian forests, ‘ōhi‘a lehua for the first 10 years after its introduction. The rust did cause severe damage to the invasive alien shrub rose apple and several native plants, especially the endangered Eugenia koolauensis. A more damaging outbreak in ‘ōhi‘a lehua trees in 2017 has increased concern.
ohia rust on E. kooaulensis photo by Edward Eickhoff via Flickr
So – while Austropuccinia psidii has an extremely wide host range, its impact in naïve ecosystems to which it might be introduced is unclear.
In most cases, lack of knowledge about a pest’s impacts on naïve hosts in new ranges is almost inevitable – unless scientists undertake host vulnerability tests. Such tests are rarely done in advance of an introduction. One exception is European scientists evaluating European trees’ vulnerability to a suite of newly discovered Phytophthora species in Vietnam and elsewhere. (I am unaware that U.S. scientists are carrying out parallel studies.)
Still, environmental and other factors play important roles and might counter expectations raised by lab experiments or experience of hosts planted in non-native sites. In Australia, McRae (2013) noted that the “mycological firestorm” predicted by environmentalists to result from introduction of the rust had not occurred. This at least partly explained waning interest in combatting the pathogen (Carnegie et al. 2016).
In my view, the swings in perceptions of the risk reflected more flaws in understanding than actual risk. Impacts can take time to manifest – especially when, as with Austropuccinia psidii – the pathogen is known to affect primarily new growth and fruit and flowers (Carnegie et al. 2016). The impact might be greatest in the form of suppressing regeneration rather than by killing mature trees right away. [See beech leaf disease as another possible example of this phenomenon.]
Questions hampering predictions of impact were further confused by taxonomic questions (Carnegie et al. 2016). Austropuccinia psidii has at least nine genetically distinct clusters. So far, two have been introduced outside South/Central America. One strain – called the “pandemic biotype” – has been found at all introduction sites in Florida, Hawai‘i, Asia, and the Pacific – Australia, New Zealand, New Caledonia (Stewart et al. 2018). This biotype is not known to be present in Brazil (Toome-Heller et al. 2020). A second biotype has been introduced to South Africa; it has been shown to be able to infect some Myrtaceae in New Zealand (Toome-Heller et al. 2020). See especially Stewart et al. 2017, full citation below.
3) Policy Barriers Created by Phytosanitary Regulations
In the U.S., the pathogen has been established in one state – Florida – since 1977. There, it is not considered to be causing damage to important species. Under U.S. regulations – reflecting the international trade rules – an organism that is already in the country cannot be treated as a “quarantine pest” unless there is an “official control program” targeting the pest. (For a discussion of this issue, see the analysis of the SPS Agreement in Chapter 3 and Appendix 3 of Fading Forests II). For this reason, when ‘ōhi‘a rust was detected in Hawai`i in 2005, USDA’s Animal and Plant Health Inspection Service (APHIS) was unable to adopt regulations governing imports or interstate movement of vectors (i.e., cuttings or nursery stock of plant species in the Myrtaceae).
The State responded to the initial detection by adopting an emergency order two years later, in August 2007. This prohibited importation of plants in the myrtle family from “infested areas”- specified as South America, Florida, and California. This state rule expired in August 2008.
It became apparent that USDA APHIS would not take action to assist Hawai`i unless APHIS accepted scientific findings as proving that additional biotypes of the rust existed that could pose a more severe threat to plants on the Islands. Such studies were undertaken, some funded by the USDA Forest Service. This process took years. During this period, Hawai`i developed a permanent rule which was adopted in May 2020. This regulation restricts the importation to Hawai`i of plants in the Myrtaceae, including live plants and foliage used in cut flower arrangements. Dried, non-living plant parts, seeds that are surface sterilized, and tissue cultured plants in sterile media and containers are exempted from the ban. Other importations may be done by permit.
Meanwhile, in 2019, APHIS proposed to include all taxa in the Myrtaceae destined for Hawai`i in an existing regulatory category of “plants for planting” not authorized for importation pending pest risk assessment (NAPPRA). The intent was to reduce the probability of introduction of additional strains of Austropuccinia psidii to the Islands. This proposal appeared 14 years after the rust was first detected in Hawai`i. And the proposal has not yet taken effect. Therefore, imports of most living plants and cut foliage are still subject only to inspection (7 Code of Federal Regulations 319.37). The tiny size of the rust spores makes detection during inspection unlikely unless the plant is displaying symptoms of the disease.
Imports of logs and lumber involving tropical hardwood species (including Eucalyptus) into Hawai`i are regulated under separate provisions which have been in effect since 1995. The wood must be debarked or fumigated [Code of Federal Regulations – 7 CFR 319.40-5(c)]. Incoming wood packaging is regulated under ISPM#15; I think it unlikely that the treatments prescribed therein would kill any rust spores present.
Policy Responses in Other Vulnerable Countries
Australia
Austropuccinia psidii had been recognized as a potentially serious biosecurity threat to Australia as early as 1985 (publications cited by Carnegie et al. (2016). The introduction of ‘ōhi‘a rust to Hawai`i so alarmed plant health and conservation officials in Australia and New Zealand that they sent representatives half way around the world to participate in the North American Plant Protection Organization’s annual meeting in Newfoundland, Canada, in October 2007! Yet interest in Australia waned when large scale tree mortality and major impacts on industries did not immediately occur (Carnegie et al. 2016). The state of New South Wales listed the rust as a Key Threatening Process to the Natural Environment, but the federal agencies rejected a petition to do the same at a national level (Carnegie et al. 2016).
Groups of scientists are carrying out research with the goal of demonstrating that the rust is already having severe effects on key species in natural ecosystems, and probably significantly affecting a wider range of species (Carnegie et al. 2016; Winzer et al. 2019; Winzer et al. 2020)
In 2018 a scientist affiliated with the Australian Network for Plant Conservation published a draft conservation plan. Its development had input from staff at the Plant Biosecurity Cooperative Research Centre and the Australian Government Department of the Environment and Energy. The goal was to help direct and stimulate further research on critical questions and build awareness of the potentially devastating effects myrtle rust might have if it remains unchecked. As of April 2020, no funding had yet become available to finalize and implement the report (Dr Michael Robinson, Managing Director, Plant Biosecurity Science Foundation).
New Zealand
New Zealand has been more aggressive in its policy approach. It adopted a strategy when Australia announced arrival of the rust in 2010. The islands had bad luck – myrtle rust is believed to have been carried to New Zealand by wind from Australia across the Tasman Sea.
As soon as the rust was first detected in 2017, two government agencies initiated broad surveys of Myrtaceae across natural and urban areas, with active outreach to citizens (Toome-Heller et al. 2020). By April 2018, it was recognized that the pathogen was too widespread to be eradicated. Significant finds were made on the western side of the North Island and at the very northern tip of the South Island (see map in Beresford et al. 2019). At that point, the government changed its focus to long-term management of the disease.
A. psidii is still very much a focus for Maori (indigenous) groups, central and local government, community groups, Myrtaceae-based industries, and research institutions.
Several research programmes are currently looking for management options, including resistance breeding (Toome-Heller et al. 2020). See research plan and reports of results to date here. However, which plant species can become infected, and under what environmental conditions, remain unclear.
New Zealand researchers have made some findings that should be of concern to forest pathologists working with all Myrtaceae:
A. psidii can overwinter as a latent infection without reproducing.
A. psidii can reproduce sexually, although the importance of the sexual cycle in seasonal epidemic development is not yet understood and teliospores have only infrequently been found in New Zealand (Bereford et al. 2019).
the unique biotype found in South Africa has already been found to be pathogenic towards some New Zealand native Myrtaceae (Toome-Heller et al. 2020).
We can expect these finding to have implications for elsewhere, including in Hawaii.
Pathways of Introduction
It is thought probable that the rust was introduced to Hawai`i on cut foliage imported from Florida. The first Australian detection was at a cut flower facility (Australian Invasive Species Council).
CABI considers plants and plant parts (including cuttings, flowers, and germplasm) to be the principal pathway. Other pathways appear to be contaminated plant waste, timber, wood packaging and dunnage; and – over short distances – contaminated equipment and tools and clothing, shoes and other personal effects.
Conclusions
The saga of myrtle rust demonstrates both the biological and technical difficulties of controlling an airborne pathogen and the inability of the existing phytosanitary system to respond to new situations. Regulatory officials are obligated to demand levels of knowledge and certainty that just are not realistic. The gap is especially great at the crucial time – before an invasion or at its earliest stage — when phytosanitary actions might be most effective.
This saga also demonstrates that efforts often wane at the management and restoration stages. At least in Hawai`i and New Zealand, government resources are still being allocated to research possible resistance breeding or other possible long-term approaches. I refer you to the article by Enrico Bonello, me, and others about the need to provide sufficient resources to such efforts in the U.S.
Sources
Australian Invasive Species Council.2011. www.invasives.org.au Environmental impacts of myrtle rust Fact Sheet February 2011
Carnegie, A.J., A. Kathuria, G.S. Pegg, P. Entwistle, M. Nagel, F.R. Giblin. 2016. Impact of the invasive rust Puccinia psidii (myrtle rust) on native Myrtaceae in natural ecosystems in Australia. Biological Invasions (2016) 18:127–144
Code of Federal Regulations. January 1, 2005 (Title 7, Volume 5). 7 CFR319.40-5: Logs, lumber, and other unmanufactured wood articles – importation and entry requirements for specified articles. (available by using search engines/retrieval services at http://www.gpoaccess.gov/fr/index.html).
Code of Federal Regulations. January 1, 2005 (Title 7, Volume 5). 7 CFR319.37: Nursery stock, plants, roots, bulbs, seeds, and other plant products – prohibitions and restrictions on importation: disposal of articles refused importation. (available by using search engines/retrieval services at http://www.gpoaccess.gov/fr/index.html).
Loope, L. and A.M. La Rosa. 2008. An Analysis of the Risk of Introduction of Additional Strains of the Rust Puccinia psidii Winter (`Ohi`a Rust) to Hawa`i. Pacific Island Ecosystems Research Center
Stewart, J. E., A. L. Ross-Davis, R. N. Graça, A. C. Alfenas, T. L. Peever, J. W. Hanna, J. Y. Uchida, R. D. Hauff, C. Y. Kadooka, M.-S. Kim, P. G. Cannon, S. Namba, S. Simeto, C. A. Pérez, M. B. Rayamajhi, D. J. Lodge, M. Agruedas, R. Medel-Ortiz, M. A. López-Ramirez, P. Tennant, M. Glen, P. S. Machado, A. R. McTaggart, A. J. Carnegie, and N. B. Klopfenstein. 2018. Genetic diversity of the myrtle rust pathogen (Austropuccinia psidii) in the Americas and Hawaii: Global implications for invasive threat assessments. Forest Pathology 48(1): 1-13. https://doi.org/10.1111/efp.12378
Toome-Heller, M. W.W.H. Ho, R.J. Ganley, C.E.A. Elliott, B. Quinn, H.G. Pearson, B.J.R. Alexander. 2020. Chasing myrtle rust in New Zealand: host range and distribution over the first year after invasion. Australasian Plant Pathology
Winzer, L.F., K.A. Berthon, A.J. Carnegie, G.S. Pegg, M.R. Leishman. 2019. Austropuccinia psidii on the move: survey based insights to its geographical distribution, host species, impacts and management in Australia. Biological Invasions April 2019, Volume 21, Issue 4, pp 1215–1225
Winzer, L.F., K.A. Berthon, P. Entwistle, A. Manea, N. Winzer, G.S. Pegg, A.J. Carnegie, M.R. Leishman. 2020. Direct and indirect community effects of the invasive plant pathogen Austropuccinia psidii (myrtle rust) in eastern Australian rainforests. Biological Invasions. Volume 22, pages2357–2369 (2020)
We know the dire threats to Hawaiian forests from pathogens. Some threaten the most widespread tree – ohia. Others are insects threatening trees and shrubs in the remnant dryland forests.
The forests of smaller islands of the Pacific also appear to be facing severe threats – although I have been unable to find information on the current situation.
Guam and its Neighbors
The forests of Guam, Palau, and others in the Western Pacific are among those threatened.
They are geographically isolated and hard to reach, but that distance has not protected them from biological invaders. Their predicament illustrates the dominant role of global movement and trade in spreading pests. In this case, it’s mostly trade in ornamental plants.
These islands have unique flora and fauna. And true to invasive species experts’ expectations, they are vulnerable to bioinvaders. Guam’s most famous invasive species is the brown tree snake (Boiga irregularis), which over a few decades eradicated many bird species and the only native terrestrial mammal, the fruit bat.
Less known, but equally damaging, have been a group of insects that are decimating Guam’s native forest flora.
The most widespread arboreal species in the forests of Guam and neighboring islands is the Micronesian cycad, Cycas micronesica. Its range is Micronesia, the Marianas Group including Guam and Rota Islands; and several of the western Caroline Islands, e.g., Palau and Yap (Marler, Haynes, and Lindstrom 2010).
These forests have already absorbed severe habitat destruction as the sites of fierce fighting in World War II and – in some cases – construction of large military bases. Still, cycads were the most common species in the forest as late as 2002 (Moore, A., T. Marler, R. Miller, and L. Yudin. Date uncertain).
The Worst Pest: Asian Cycad Scale
The most severe current threat to the cycads are introduced insects, especially the Asian cycad scale Aulacaspis ysumatsui.
The cycad scale is native to Southeast Asia. It was first detected on Guam in 2003, when officials noticed that cycads planted near hotels had begun to die. However, this scale had already been spreading thanks to the trade in ornamental cycads. It was detected in Florida in 1996, on Hawai`i in 1998. It continued to spread rapidly in the western Pacific: to Rota in 2007, Palau in 2008 (University of Guam 2012). By late 2019, the scale had spread globally – numerous islands and neighboring mainland areas in the Caribbean (including Puerto Rico and US Virgin Islands), several US states in the Southeast, California, and Taiwan (Moore, Marler, Miller, and Yudin. Date uncertain.) and South Africa. (vanWilgen, et. al. 2020) Also, see the map prepared by CABI.
In every case, the scale has apparently been spread on nursery stock. It is difficult to contain by standard phytosanitary measures – visual inspection – because the scale is tiny and hides deep in the base of the plant’s stiff leaves and other crevices. (Marler and Moore 2010)
By 2005 the scale was killing the native cycad on Guam. Within four years, the millions of C. micronesica on Guam were reduced by more than 90% (Marler, T.E. and K.J. Niklas. 2011). The last time cycads on Guam reproduced in any significant number was in 2004 (Marler and Niklas 2018).
The severe impact of the scale was so rapid that the International Union for Conservation of Nature and Natural Resources (IUCN) changed its listing of C. micronesica from “near threatened” in 2003 to “endangered” in 2006. (IUCN Red List of Threatened Species Online 2008).
Scientists have made several attempts to introduce a biocontrol agent. However, the most promising – the lady beetle Rhyzobius lophanthae – has failed to control the scale, despite having become virtually ubiquitous on Guam. The beetle is too big to reach the significant proportion of scale insects living in small cracks and voids within the plant structures. Evidence from another cycad species indicates that the beetles also don’t prey on scale insects living beneath trichomes (fine hairlike structures on the leaves) or on parts of the plant close to the ground. (Moore, Marler, Miller, and Yudin. Date uncertain.).
Attempts to introduce a second biocontrol organism – the parasitoid wasp Aphytis lignanensis – were stymied by the presence of R. lophanthae (Moore, Marler, Miller, and Yudin. Date uncertain).
Micronesian cycad photo by Lauren Gutierrez
Other Invasive Species Attacking Cycads
The cycad blue butterfly (Chilades pandava) was detected in 2005 and spread throughout Guam within months (IUCN 2009). Also, it’s been found on Saipan (1996) and Rota (2006). The butterfly is native to southern Asia from Sri Lanka to Thailand and Indonesia. High populations can cause complete defoliation of new foliage. Repeated defoliations can kill the plant. Cycads on Guam are particularly vulnerable because the scale has already caused loss of most of their leaves. Butterfly larvae are often protected by ants (Anonymous).
On cultivated plants the butterfly can be controlled by microbial insecticides containing Bacillus thuringiensis kurstaki (Moore). Scientists at the University of Guam are exploring use of injected insecticides (Moore). They have found an egg parasite, but parasitism levels are low. Any biocontrol agent targetting larvae would have to contend with the ants (Anonymous).
A longhorned beetle (Dihammus (Acalolepta) marianarum) and a snail (Satsuma mercatorius) are also feeding on the cycads (Marler 2010).
The Indo-Malayan termite Schedorhinotermes longirostris was detected in 2011. The termites weaken the cycad stems, which are then toppled by feeding by introduced deer. The termites are also damaging the cycad’s reproductive structures (megastrobili). Termite attacks on cycads surprised scientists since cycads do not form true wood. The termite had probably been introduced recently because, as of 2011, it had been detected only near the Andersen Air Force Base airport (Marler, Yudin, and Moore 2011).
More Isolated – but Still Overrun
Scattered across the Pacific are groups of atolls, including Palmyra and Rose.
Despite their distance from other islands, they have all been visited by mariners for centuries. As a result, they have non-native species, including insects that attack trees.
Pisonia tree forest – Wikimedia
The tree most affected is pisonia – Pisonia grandis.
The principal insect is another scale, Pulvinaria urbicola. There are some reports that the scale is farmed by ants; species mentioned include several introduced species such as the yellow crazy ant, Paratrechina longicornis.
The scale is probably from the West Indies. Once it reached the Pacific, it might have been distributed to additional islands on seabirds, which travel long distances between the atolls.
The scale’s impact is unclear.
At first, in the mid-2000s, impacts seemed dire. It was reported to be causing widespread tree death on Palmyra and Rose atolls, islands around northeastern Australia, in the Seychelles, and possibly in Tonga.
However, in 2018, scientists reported that eradication of rats on Palmyra Atoll had resulted in an immediate spurt of reproduction of a tree. Numbers of “native, locally rare tree” seedlings (possibly but not explicitly said to be Pisonia grandis) jumped from 140 pre-eradication to 7,756 post-eradication (in 2016). The study made no mention of the scale.
Rose Atoll has only one small island (6.6 ha) with vegetation. Before 1970, it was dominated by Pisonia grandis, but by 2012, there were only seven trees on the island. Several possible causes of this decline have been suggested. Other than the scale, suggested causes include storms, drought, rising sea level / saltwater incursion, and imbalance of bird guano-derived nutrients in the soil. [All information about Rose Atoll is from Peck et al., 2014)
A survey carried out in April 2012 and November 2013 detected 73 species of arthropods from 20 orders on Rose Island, including nine ant species (all but one non-native). Two of these ants – Tetramorium bicarinatum and T. simillimum – were detected tending the scales on Pisonia.
The survey found no evidence of natural enemies of the Pulvinaria scales.
The scientists tested treatment of Pisonia with the systemic insecticide imidacloprid. This treatment apparently reduced scale populations considerably for several months, but then they began to build up again.
In contrast to Palmyra, Polynesian rats (Rattus exulans) were eliminated from Rose Atoll in 1990–1991 – so their role in destroying the trees had ended 20 years before the study. What does the continued decline of the Pisonia trees in subsequent decades suggest for the future of Pisonia trees on Palmyra?
I have sought updates on the tree-pest situations on Guam and the other Pacific islands, but my queries have not received a reply.
CABI November 2019. Aulacaspis yasumatsui (cycad aulacaspis scale (CAS)) or the Asian cycad scale. https://www.cabi.org/isc/datasheet/18756 (was formerly Commonwealth Agricultural Bureaux (CAB) International; now apparently just uses acronym)
Marler, T.E. pers. comm. August 15, 2012
Marler, T.E. 2010. Cycad mutualist offers more than pollen transport. American Journal of Botany, 2010; 97 (5): 841. Viewed as materials provided by University of Guam, via EurekAlert; accessed 6 August, 2012.
Marler, T., Haynes, J. & Lindstrom, A. 2010. Cycas micronesica. The IUCN Red List of Threatened Species 2010: e.T61316A12462113. http://dx.doi.org/10.2305/IUCN.UK.2010-3.RLTS.T61316A12462113.en Accessed 22 April, 2020.
Marler, T.E., and A. Moore. 2010. Cryptic Scale Infestations on Cycas revoluta Facilitate Scale Invasions. HortScience. 2010; 45 837-839. Retrieved August 6, 2012 from www.eurekalert.org
Marler, T.E. and K.J. Niklas. 2011. Reproductive Effort and Success of Cycas micronesica K.D. Hill Are Affected by Habitat. International Journal of Plant Sciences, 2011; 172 (5): 700. Viewed as materials provided by University of Guam, via EurekAlert; accessed 6 August, 2012.
Peck, R., P. Banko, F. Pendleton, M. Schmaedick, and K. Ernsberger. 2014. Arthropods of Rose Atoll with Special Reference to Ants and Pulvinaria urbicola scales (Hemiptera: Coccidae) on Pisonia grandis trees. Hawaii Cooperative Studies Unit. University of Hawaii. Technical Report HCSU-057 December 2014
vanWilgen, B.W.,J. Measey, D.M. Richardson, J.R. Wilson, T.A. Zengeya. Editors. 2020. Bioinvasions in South Africa. Invading Nature. Springer Series in Invasion Ecology 14.
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 These reports do not include details on the pest situation on the Pacific islands (including Hawai`i).
Last month, in my blog about the US Geological Survey’s report on invasive species I announced release of a report by South Africa on its invasive species management programs – available here. Because this report is unusual in both its rigor and its honesty, I’m returning to it here. I think it is a model for our country and others.
The report provides the basics. That is, it analyzes pathways of introduction and spread; number, distribution and impact of individual species; species richness and abundance of alien species in defined areas; and the effectiveness of interventions. Of the 775 invasive species identified to date, 556, or about 72%, are listed under some national regulatory program. Terrestrial and freshwater plants number 574 species; terrestrial invertebrates number 107 species. A different set of 107 species, or about 14%, are considered by experts to be having major or severe impacts on biodiversity and/or human wellbeing. The highest numbers of alien species are in the savanna, grassland, Indian Ocean coastal belt, and fynbos biomes. South Africans are particularly focused on the reductions in surface water resulting from plant invasions. Much of the control effort is under the egis of the decades-old “Working for Water” program.
Also, the report has features that are all-too-rare in work of its kind. First is the authors’ focus on rigor – of data sources and interpretation of those data using standardized criteria. Second – and even more important – is their call for analyzing the efficacy of the components of invasive species program. They insist on the need to measure outcomes (that is, results), not just inputs (resources committed) and outputs (“acres treated”, etc.). Inputs are far easier to measure and are, unfortunately, the mainstay of how most U.S. efforts are tracked – if they are tracked at all.
As they note, measure of inputs and outputs are not useful because they provide no guidance on the purpose of the action or treatment or of its effectiveness in achieving that purpose.
(For earlier CISP advocacy of measuring outcomes, visit the National Environmental Coalition on Invasive Species and read the bullet points under “Recommendations for a Comprehensive National Response”.)
The report has been praised by international conservationists, including Piero Genovesi – chair of the IUCN’s Invasive Species Specialist Group. British ecologist Helen Roy says that, to her knowledge, it is “the first comprehensive synthesis of the state of invasive species by any country.”
How well are programs working?
The authors’ focus on rigor includes being scrupulously honest in their assessments of current program components. They note deficiencies and disappointments, even when the conclusions might be politically inconvenient. To be fair, all countries struggle to achieve success in managing bioinvasions. And South Africa is, in many ways, a developing country with a myriad of economic and social challenges.
So it is probably not surprising that, for most factors analyzed, the authors say data are insufficient to determine the program’s impact. Where data are adequate, they often show that programs fall short. For example, they conclude that control measures have been effective in reducing populations of established invasive species, usually plants, in some localized areas but not in others. While the situation would arguably have been worse had there been no control, current control efforts have not been effective in preventing the ongoing spread of IAS when viewed at a national scale. Only one of South Africa’s 72 international ports of entry has consistent inspection of incoming air passengers and cargo – and even those inspections are not carried out outside of regular working hours (e.g., nights and weekends).
The authors are even critical of the “Working for Water” program – which is the basis for most control efforts in South Africa and enjoys wide political support. WfW has two goals: providing employment and development opportunities to disadvantaged individuals in rural areas, and managing invasive alien plants. Despite substantial funding, the WfW program has supported control teams that have reached only 2% – 5% of the estimated extent of the most important invasive plants. Furthermore, programs structured to provide employment have not ensured use of the most efficient control strategies.
What’s needed in South Africa — and around the world
The authors conclude that South Africa needs new processes to monitor and report on bioinvasions in order to achieve evidence-based policy and management decisions. They call for (1) more research to determine and assess invasive species impacts; (2) better monitoring of the effectiveness of current control measures; and (3) the development of methods to look at the impact of bioinvasions and their management on society as a whole.
The authors say it is important for South Africa to improve its management of invasive species because their impacts are already large and are likely to increase significantly. They note that improving management efficiency will require difficult choices and trade-offs. They recommend a focus on priority pathways, species, and areas. They also stress return on investment.
I don’t know how this report has been received in South Africa. I hope government officials, media observers, landowners, political parties, and other stakeholders appreciate the honesty and expertise involved. I hope they take the analyses and recommendations seriously and act on them.
(Preparation of the report was was overseen by a team of editors and contributing authors employed by the South African National Biological Diversity Institute (SANBI) and the DST-NRF Centre of Excellence for Invasion Biology at (C.I.B). Drafts were widely circulated to contributing authors and other stakeholders for comments. An independent review editor will be appointed to assess the review process and recommend any ways to strengthen the process for future reports.)
Meanwhile, how do we Americans apply the same rigor to analyzing our own efforts?
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.
Phytophthora cinnanomi killing Ione manzanita in California; photo from Swiecki and Garbelotto, Distribution of Phytophthora cinnamomi within the range of Ione manzanita (Arctostaphylos myrtifolia). Agreement between the California Department of Fish and Game and University of California
Phytophthora species are plant pathogens in the oomycote group (water molds, closely related to brown algae). More than 160 species have been described; new species are continually being isolated. Many Phytophthora species are deadly to naïve hosts; examples in the United States include sudden oak death, Port-Orford cedar root disease, disease on chestnuts and oaks.
Forests in Europe – especially the United Kingdom – and Australia are also suffering high levels of mortality associated with one or more Phytophthora species.
In recent years, several studies have documented the role of nurseries in spreading non-native Phytophthora species. Two strains of P. ramorum are widespread in European nurseries and in tree plantations and wild heathlands of southwest England, Wales, parts of Scotland, and Ireland. (See here and here.)
In April 2016 I blogged about the situation in Europe described by Jung et al. 2015 (see references at the end of the blog). Jung et al. concluded that diseases caused by Phytophthora pose a substantial threat to both planted landscapes and forest ecosystems across Europe. They found 56 Phytophthora taxa in 66% of 2,525 forest and landscape planting sites that were probably introduced to those sites via nursery plantings.
Barber et al. 2013 reported nine species of Phytophthora associated with a wide variety of host species in urban streetscapes, parks, gardens, and remnant native vegetation in urban settings in Western Australia. Phytophthora spp were recovered from 30% of sampled sites.
A new summary confirms that the threat is similar in North America. In British Columbia, Dale et al. (2017) found more than two times as many Phytophthora species were detected in soil and water samples in urban areas (23) than in natural areas (11). Urban samples also showed a much higher diversity of Phytophthora per site than natural environments. These Phytophthora species had been introduced initially into urban areas and had subsequently spread into native vegetation, particularly in areas near developed sites (wildland-urban interface areas).
Swiecki et al 2018 cite several sources and their own studies to show that the large and increasingly diverse contingent of introduced Phytophthora species pose an increasingly important threat to both urban forests and surrounding native forests and plant communities in California. It is clear that shrubs and herbaceous plants as well as trees are also at risk. These scientists have repeatedly found multiple non-native Phytophthora species at individual sites in northern and southern California sites where nursery stock had been planted. Sampling in 2014 identified about 60 different Phytophthora taxa in restoration planting sites and native plant nurseries. The sampled restoration plantings were mostly located in urban riparian corridors and peri-urban parks, open spaces, or protected watersheds.
I first discussed this issue in a blog in July 2016.
Swiecki et al (2018) have also found that Phytophthora species persist in drier ecosystems. When conditions are too dry for sporangium production, Phytophthora hyphae produce resistant survival structures that can tolerate drying and persist in dead root fragments or soil. In the presence of appropriate stimuli, e.g., moisture and root exudates, resistant structures germinate to produce sporangia or hyphae, leading to new infections. Even relatively short wet periods associated with rain or irrigation can be sufficient to stimulate zoospore release. Swiecki et al (2018) list examples of numerous Phytophthora infestations that developed in dry sites, such as dry foothills of the Sierra Nevada in Amador County, and the Oakland Hills of Alameda & Contra Costa County. Swiecki et al. (2018) also note that P. cinnamomi has persisted in Australian forests in the absence of known primary hosts.
Phytophthora infections can also persist for decades in soil. In California, Swiecki et al. (2018) mention several examples:
Residual cinnamomi inoculum killed young sprouts of susceptible manzanitas (Arctostaphylos myrtifolia and A. viscida) planted on sites that were infected many years earlier.
A street planting of cork oaks (Quercus suber) apparently died due to Phytophthora root rot that had occurred 21 years earlier.
Both cinnamomi and P. cactorum were recovered from roots and soil beneath affected trees at least 60 years after the site had been a municipal woody plant nursery and adjacent residence.
A 7-acre area of native vegetation showing decline & mortality of multiple plant species was infested with multiple Phytophthora spp, including cactorum, P. cambivora, P. crassamura, P. ‘kelmania’ & P. syringae. The site was apparently infected 22 years earlier during a planting of a habitat restoration project using Ceanothus nursery stock. Subsequent spread was primarily downhill from the planting sites, facilitated by water flow, with additional spread along and near trails.
The Risk from the Nursery Trade
While Phytophthora-infested soil and plant debris can be transported on tools, vehicles, and shoes, or moved in large quantities when infested soil is excavated, graded, or imported, the principal threat is the nursery trade.
Jung et al. (2015) state that widespread contamination of nursery stock was the primary means by which these pathogens were introduced and spread in Europe. They found 49 Phytophthora taxa in 670 European nurseries. Phytophthora species were recovered from more than 90% of the sampled nurseries.
Swiecki et al. (2018) say that most of the common Phytophthora species detected in California are distributed globally, moved about with live plants or other infested materials. None is native to California.
Swiecki et al. (2018) cite studies reporting that thirteen species of Phytophthora were found in a survey for leaf spots in California nurseries in 2005 and 2006. Sampling of plants in or originating from Calif native plant nurseries alone has yielded about 60 Phytophthora At least eight species of Phytophthora were found in shipments of symptomatic and asymptomatic plants sent from west coast nurseries to Maryland. Parke et al. (2014) identified 28 Phytophthora taxa in four Oregon nurseries.
Not all infections are on the West Coast. Swiecki et al. (2081) reports that a survey in Minnesota nurseries of plants with symptoms – primarily on aboveground plant parts – found eleven species of Phytophthora.
Are scientists in other parts of the country looking for Phytophthora? I see no reason to think the situation in California is unique.
The damage caused by Phytophthora infections can be significant. In California and Oregon, sudden oak death, and Port-Orford cedar root disease, have killed well over a million trees and disrupted the ecosystems of which they are a part. There are multiple locations in Northern California where introduced Phytophthora species, especially P. cinnamomi and P. cambivora, have caused localized to extensive decline and mortality in native forests and shrublands.
Phytophthoradieback has infected more than one million hectares in Western Australia. More than 40% of the native plant species of the region are vulnerable to the causal agent, P. cinnamomi.
Phytophthora dieback in Western Australia
Dieback in native forest in Western Australia; photo copyright Western Australian Department of Parks and Wildlife
In the United Kingdom, several Phytophthora species are causing widespread mortality of native shrubs and trees and commercial plantings.
In nearly all the studies, scientists have detected previously unknown pathogen-host relationships.
The threat from spreading pathogens with wide host ranges is not limited to the genus Phytophthora. The fungus Fusariumeuwallacea associated with the Kuroshio and polyphagous shot hole borers is known to kill at least 18 species of native plants in California and additional species in South Africa. The laurel wilt fungus kills many trees and shrubs in the Lauraceae family. ‘Ohi‘a or myrtle rust kills several shrubs native to Hawai`i and threatens a wide range of plants in the Myrtaceae family in Australia and New Zealand. Some insects also have wide host ranges, including the Kuroshio and polyphagous shot hole borers; and Asian longhorned and citrus longhorned beetles.
When are national and international phytosanitary agencies going to adopt policies and programs that are effective in preventing the continued spread of these highly damaging tree-killing pests? At the national level, APHIS needs to aggressively use two authorities to curtail importation of plant taxa from countries of origin which present a risk of transporting additional species of pathogens:
NAPPRA, which allows APHIS to prohibit risky imports until it has conducted a pest risk analysis.
Programs under the revised “Q-37” regulations allowing APHIS to work with exporting countries’ phytosanitary officials to implement integrated pest management strategies to ensure that plants are pathogen-free before they are exported.
I have blogged about both programs before – NAPPRA here; the Q-37 regulation strengthening here.
At the international level, the members of the International Plant Protection Convention (IPPC) must recognize the failure of the international phytosanitary system and explore ways to strengthen it. See my numerous blogs on this topic (beyond those linked to here!) by visiting www.cisp.us or www.nivemnic.us and searching under the category “forest pathogens”.
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.
SOURCES
Jung, T. et al. 2015 “Widespread Phytophthora infestations in European nurseries put forest, semi-natural and horticultural ecosystems at high risk of Phytophthora disease” Forest Pathology. November 2015; available from Resource Gate
Swiecki, T.J., E.A. Bernhardt, and S.J. Frankel. 2018. Phytophthora root disease and the need for clean nursery stock in urban forests: Part 1 Phytophthora invasions in the urban forest & beyond. Western Arborist Fall 2018
Apparently can’t access current (2018) issues of “Western Arborist” on web unless subscribe
While I usually blog about insects (and plant pathogens) that have invaded new ecosystems and are killing native plant species, I am aware that insects are numerous and vitally important components of the ecosystems in which they evolved. I join others in noting with concern evidence that insect populations in wide-apart areas have declined at very high rates. Insects appear to be affected by the Sixth Extinction Event (concept described here and here) as much as or possibly more than various vertebrate and plant taxonomic groups.
The Zoological Society of London and World Wildlife Fund published this week the 2016 version of the Living Planet report. Based on an analysis of 3,700 vertebrate species (birds, fish, mammals, amphibians and reptiles), the authors concluded that global wildlife populations have fallen by 58% since 1970 (Morelle; see references at the end of the blog).
Dirzo et al. in 2014 provided a very interesting discussion of the impacts of species’ declines in numbers and local extinctions – short of complete extinction. They asserted that “declines in numbers of individuals in local populations and changes in the composition of species in a community will generally cause greater impacts on ecosystem function than global extinctions. Dirzo et al. noted the importance of invertebrates, especially insects, in ecosystem functioning. They stated that the smaller fauna – including insects – “arguably are more functionally important” than charismatic megafauna and called for improved monitoring and study of such taxa, particularly invertebrates,
In their study, Dirzo et al. estimated that, since 1970, Lepidoptera – an order containing many important pollinators – had declined 35% in abundance globally over 40 years. Declines of other insect orders were considerably more. One study they cited found an overall 45% decline for all invertebrate populations over 35 years. More recent studies find decline rates that considerably exceed the estimated decline of 58% in global abundance of wild vertebrates over a 42-year period (Morelle; Hallmann et al.)
A year ago, Hallmann et al. reported a 76% decline in the biomass of flying insects over a 27-year period in Germany. There were seasonal variations; in midsummer, when insect biomass is highest, the decline was 82%. The study was carried out in nature protection areas – that is, places set aside and protected to conserve biological diversity. Hallmann et al. predict cascading effects on food webs and jeopardy to ecosystem services, including pollination, herbivory and breakdown of detritus, nutrient cycling and providing a food source for higher trophic levels such as birds, mammals and amphibians.
Hallmann et al. said that changes in weather, land use, and habitat characteristics could not explain this overall decline. Declines occurred in both nutrient-poor habitat types (e.g., heathlands, sandy grasslands, and dunes) and nutrient-rich habitats (grasslands, margins and wasteland), as well as in pioneer and shrub communities.
Another of the few studies looking at insects broadly, a study of flying insect biomass in the United Kingdom, found a biomass decline at only one of the four sites. Hallmann et al. note that the British researchers used considerably different sampling methods that targetted primarily high-flying insects (and caught mostly members of one fly family) whereas their own Malaise traps caught insects flying close to the ground and a much wider diversity of taxa.
Taxon-specific studies have also found severe declines in insect populations.
Hallmann et al. concluded that the scale of decline in insect biomass – throughout the growing season, and irrespective of habitat type or landscape configuration – suggest that large-scale factors must be involved. As noted, their data did not support either landscape changes or climate change as explanatory factors – although they admit that they did not exhaustively analyze the full range of climatic variables that could potentially impact insect biomass. Hallmann et al. did think that agricultural intensification (e.g. pesticide usage, year-round tillage, increased use of fertilizers and frequency of agronomic measures) was a plausible cause of insect biomass decline given the reserves’ limited size in typically fragmented western-European landscapes. The noted that the protected areas might serve as insect sources which might be counterbalanced by the surrounding agricultural fields, which might act as sinks or ecological traps.
While Hallman et al. did not specify the types of pesticides being used by the German farmers operating near their study areas, in recent years there has been growing concern about widespread use of neonicotenoids, which appear to pose a threat to bees and possibly other insects. Three sources of information are the European Food Safety Agency; Xerxes Society; and petition pertaining to regulation of seeds treated by neonicotenoids submitted by the Center for Food Safety.
This month, Bradford Lister and Andrés García published a study that compared numbers of the insects and insectivores (birds, frogs, lizards) in Puerto Rico’s tropical rainforest in 2012 to results of Lister’s studies there in 1976 and 1977. Overall arthropod biomass in Puerto Rico’s Luquillo rainforest fell 10 to 60 times since 1970s (Lister and Garcia). Numbers of insects in the vegetation collected by sweep nets decreased to a fourth or an eighth of what they had been. The catch rate of ground-dwelling arthropods caught in sticky traps fell 60-fold (Guarino).
Lister and Garcia attribute the crash in arthropod numbers to climate change, especially rising maximum temperatures. They note that over the same 40-year period, the average high temperature in the rainforest increased by 4 degrees Fahrenheit (2oC). Lister and Garcia cite several studies indicating that tropical invertebrates are adapted to a narrow band of temperatures.
Lister and Garcia also measured declines among insect-feeding vertebrates. The biomass of anole lizards dropped by more than 30%. Some anole species disappeared from the interior forest (Guarino). Declines in number of coqui frogs (Eleutherodactylus spp) began in the 1970s. Currently, three of 16 species are extinct, and the remaining 13 species are classified in some category of endangered or threatened. Disease caused by the fungus Batrachochytrium dendrobatidis is not a factor at the elevations where study done.
Anolis gundlachi; photo by Joe King
Citing data from other researchers, Lister and Garcia report that numbers of insectivorous birds captured in mist nets fell 53% between 1990 and 2005.
Lister and Garcia sought to explain why there were simultaneous, long-term declines in arthropods, lizards, frogs, and birds over the past four decades in the relatively undisturbed rainforests of northeastern Puerto Rico. They concluded that climate warming has been a major factor driving reductions in arthropod abundance, and that these declines have in turn precipitated decreases in forest insectivores in a classic bottom-up cascade.
As supporting evidence, Lister and Garcia cite
(1) Declines across varied species and communities that occurred in parallel with rising temperatures.
(2) Simultaneous declines of all arthropod taxa in their own and others’ studies – pointing to an overriding environmental factor that has had ubiquitous, adverse effects on forest arthropods regardless of taxonomic affiliation, stratum occupied, or type of niche exploited.
(3) Declines in arthropod abundance that occurred despite major decreases in their predators – and, presumably, reduced predatory pressure..
Lister and Garcia note that there have been almost no significant human perturbations in the Luquillo forest since the 1930s, and that pesticide use in Puerto Rico fell nearly 80% over the past 40 years with the decrease in agricultural activity on the island. Some of the insect trend data came from studies carried out in the Luquillo Long Term Ecological Study site.
Lister and Garcia say that major weather perturbations have also had an impact. Over the 36-year time span, there have been five major hurricanes and eight severe droughts. They note that the island’s vegetation regenerated rapidly after hurricanes Hugo and Maria; insect populations regenerated rapidly after Hurricane Georges. La Niña episodes led to an immediate increase in the abundance of canopy invertebrates, whereas El Niño episodes caused declines.
Of course, some insects are under threat from loss of their primary food plants to invasive species. I note particularly the Palamedes swallowtail butterfly (Papilio palamedes), which depends on redbay and swamp bay, and an estimated 21 species of North American butterflies and moths believed to specialists or largely dependent on ash.
In some cases, e.g., hemlock woolly adelgid and Asian longhorned beetle, neonicotenoids, specifically imidacloprid, is an essential tool to controlling a tree-killing invasive insect.
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.
SOURCES
Dirzo, R., H.S. Young, M. Galetti, G. Ceballos, N.J. B. Isaac, B. Collen. 2014. Defaunation in the Anthropocene. Science 345, 401
Guarino, B. 2018. ‘Hyperalarming’ study shows massive insect loss. 2018. The Washington Post October 15 2018
Hallmann CA, Sorg M, Jongejans E, Siepel H, Hofland N, Schwan H, et al. 2017. More than 75 percent decline over 27 years in total flying insect biomass in protected areas. PLoS ONE 12 (10): e0185809. https://doi.org/10.1371/journal. pone.0185809
Lister, B.C. and A. Garcia. 2018. Climate-driven declines in arthropod abundance restructure a rainforest food web. Proceedings of the National Academy of Sciences. http://www.pnas.org/content/early/2018/10/09/1722477115
tanoak killed by sudden oak death; Marin County, Calif. photo F.T. Campbell
Here is some interesting information from recent issues of the the California Oak Mortality Task Force’s bimonthly newsletter. I am updating my earlier blogs on the status of Phytophthoras and sudden oak death (SOD) in the United States and Europe.
More than 600 samples were taken from streams or ponds in nine states (Alabama, Florida, Georgia, Mississippi, North Carolina, Pennsylvania, South Carolina, Tennessee, and Texas) during 2016. Ten of the samples were positive: seven from three streams in Alabama and three from one stream in Mississippi. Each of these had tested positive before; none was a new positive location. [March newsletter]
The disease continues to spread in Oregon and California:
During 2016 and early 2017, sudden oak death and tanoak mortality continued to intensify within the officially designated quarantine zone in southwest Oregon. So far, no new outbreaks have been detected outside the quarantine zone.
In Oregon, there is growing concern about the disease and the paucity of funds to address it. As a result, Oregon state Representative David Brock Smith and U.S. Senator Jeff Merkley have formed an Oregon Sudden Oak Death Task Force. The Task Force is developing a collaborative action plan to secure enough funding to contain the infestations of the NA1 genetic strain (the one widespread in Oregon and California) and to eradicate the EU1 lineage (this is the only known site where this strain is established in the forest in North America; see my blog from August 2015, which explains the significance of these strains.) [March newsletter]
In California, scientists have been surprised by the intensity of the disease in several parks on the eastern side of San Francisco Bay – an area that is drier than most forests that are infested. The severe drought of recent years has not prevented spread of the disease. Even more surprising, one park has very little California bay laurel – which is considered to be the primary source of infection. [March newsletter]
Native plant nurseries may be spreading various Phytophthoras (see my blog from last year here) or the presentations on “Phytophthora Detections in Native Plant Nurseries and Restoration Sites” posted here)
The National Ornamentals Research Site at Dominican University (NORS-DUC) sampled several types of native plant nurseries in fall 2016 to determine the extent of movement of Phytophthora species on plants they sell. Unfortunately, the report in the newsletter did not include results of the sampling. [January 2017]
CFDA photo of herbaceous plants with Phytophthora infection
Oregon and Washington authorities acted in response to the initial reports from the San Francisco area, and sampled nurseries in their states. They found a similarly high infestation rate in native plant nurseries in their states. Washington State University and Oregon State University have held several 2 ½-day workshops on “Preventing Phytophthora Contamination in Native Plant Nurseries and Restoration Sites”. [May newsletter]
For more information about Phytophthoras in native herbaceous plants in California, visit http://ucanr.edu/sites/sod6/Proceedings/Presentations_and_Posters/ and www.calphytos.org
Disease costs in England and Wales could top 1 billion dollars
Drake and Jones have estimated that damage by Phytophthora ramorum and P. kernoviae [link to Gallery] to non-extractive public use and non-use values at risk from uncontrolled spread of these diseases in England and Wales is £1.446 billion per year (approximately $US 1.82 billion). The greatest public value at risk (slightly more than one-third) is from an uncontrolled spread of these diseases to heritage gardens; lower risks are to the diseases’ spread to woodlands and heathlands. [March newsletter]
5) Ireland resembles Europe in numbers of Phytophthora species:
O’Hanlan and colleagues tested more than 11,000 samples from both “trade” environments (presumably, nurseries) and “non-trade” environments (presumably plantings or natural environments). They detected 19 species and 3 informally designated taxa of Phytophthora, including 8 new records for Ireland. Thus, Ireland’s situation is similar to that in Europe more broadly – a study last year by Junker and colleagues report the detection of 15 Phytophthora species in two commercial woody ornamental nurseries [link to blog about Phythophs in Europe] In Ireloand, P. ramorum was found on 30 hosts; P. syringae on 6 hosts; P. kernoviae on 3 hosts. Phytophthora species were most frequently detected on rhododendrons – (12 Phytophthora species). [January newsletter]
SOURCES
Drake, B. and Jones, G. 2017. Public Value at Risk from Phytophthora ramorum and Phytophthora kernoviae Spread in England and Wales. Journal of Environmental Management. 191: 136–144.
Junker, C., Goff, P., Wagner, S., and Werres, S. 2016. Occurrence of Phytophthora in commercial nursery production. Plant Health Progress. 17:64-75.
O’Hanlon, R.; Choiseul, J.; Corrigan, M.; Catarame, T.; and Destefanis, M. 2016. Diversity and Detections of Phytophthora Species from Trade and Non-Trade Environments in Ireland. EPPO Bull. 46: 594–602. DOI: 10.1111/epp.12331.
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.
Officials who carry out plant health programs around the world are trying to build public understanding and support for such programs by organizing an “International Year of Plant Health”. Such “international years” are designated by the United Nations General Assembly – so – as you can imagine – years of planning go into the effort.
So far, the proposal has been approved by the Council of Agricultural Ministers and will be considered by the Conference of the UN Food and Agriculture Organization in June 2017. If approved by the FAO, the proposal will then be put to the full United Nations by sponsoring nations’ diplomats. The General Assembly meeting in 2018 would consider the proposal – assuming FAO does forward it.
The goal of the proposed Year is to persuade decision-makers and the public that protecting plants by preventing and containing pests is an essential foundation for countries’ efforts to achieve food security, economic development, and environmental protection. Organizers also want people to know that plant protection is also a necessary component of policies to facilitate trade.
The events associated with the “International Year of Plant Health” will recognize plant health disciplines and the many people and organizations who contribute at the global, regional and national levels. It is not intended to celebrate specifically the International Plant Protection Convention, or the standards and other measures it has adopted.
Plant health professionals are concerned that funds and other resources dedicated to plant protection services are shrinking despite the growing threat to agricultural and natural resources from the spread of pests. Without more attention, they fear that resources will fall even farther behind the need as agencies confront demands from other global challenges. They intend to make the case that healthy plants help solve — rather than compete with – such other big problems as climate change, changing migration patterns, biosecurity concerns, and economic development.
The proponents specific objectives are to:
Raise awareness among political decision makers at global, regional, and national levels.
Build up plant health efforts and resources at all levels to better match growing needs linked to increasing trade and the new pest risks caused by climate change.
Educate the broader public so it better understands the importance of protecting plant health.
Enhance dialogue and stakeholder involvement in plant health.
Increase information about the state of plant protection in the world.
Promote partnerships on national, regional, and global levels.
It is hoped that success in raising awareness and understanding will result in sustainable funding of national plant health systems that will, in turn, enable
Improved capacity to take on more plant health related projects and programs
More effective collaboration and solutions at the global level
Better plant health situation in all countries.
I assume that readers of this blog are stakeholders in the global plant protection network. Most of you are professionally engaged in forest or nature conservation (perhaps through research), or are active conservation advocates. Some of you might be affiliated with trade and grower associations. Please consider how you can help educate political decision makers about the importance of protecting plants from non-native organisms that potentially threaten native ecosystems or agricultural and horticultural production. The first task is to ensure that the incoming Secretary of Agriculture actively supports the proposal both among his colleagues (e.g., with the Department of State) and at the FAO Conference in June. Please use your contacts in the government – including the Congress – and with other stakeholders to promote the idea.
Assuming that the International Year of Plant Health is approved, there will be many opportunities to lead or collaborate in the planned outreach efforts. Our engagement might help shape the message. For example, we need to ensure attention to the many challenges currently hindering plant health protection, as discussed in my blogs and in numerous peer-reviewed articles and reports. Also, we need to make certain that the environmental and biodiversity aspects of plant protection are prominent among considerations.
And if the Year is not approved? In my mind, that action would prove even more that we need to educate those who do not yet see why healthy trees and other plants matter!
Let me know what you think we might do – by sending me an email using the “contact us” button. Together, we can use this proposal to join coalitions with the goal of promoting stronger, more effective protection for our forests and other natural resources!
Posed 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 uncivil or inflammatory.
Maartje J. Klapwijk and several colleagues have recently taken a hard look at non-native forest pests in Europe. They conclude that current European legislation is inadequate to prevent forest/tree pest introduction, establishment and spread in the European Union. (A link to the article is provided at the end of this post.)
Some of the proactive steps that they recommend, however, will be difficult to enact. International trade rules (World Trade Organization, Agreement on the Application of Sanitary and Phytosanitary Measures – SPS Agreement) require that countries prove that the target commodity in trade presents a significant pest risk – proof that is difficult to obtain before damage has actually occurred.
(I have written extensively about this “Catch 22” – see Fading Forests II here)
Furthermore, European Union rules prevent countries from taking proactive measures to restrict potentially pest-infested plants or wood products being traded from one EU member country to another. However, member countries’ vary in their levels of concern about tree-killing pests. As a result, phytosanitary measures are quite weak in some countries. Once a pest-infested shipment enters a country with a weak phytosanitary system it can be moved freely to any other member country.
Thus, international and EU rules together create a significant risk that a pest will enter, establish, and then be spread by commerce to the rest of the Union.
The authors note that growing trade in living plants and wood products has brought a rise in non-native tree pests becoming established in Europe. The number of alien invertebrate species has increased two-fold since 1950; the number of fungal species has increased four-fold since 1900. Few studies have attempted to quantify the economic impacts of non-native tree-killing pests in Europe. But the authors say that the introduced pests will cause economic damage either directly by reducing the revenue of the country or imposing control costs; or indirectly through trade restrictions or reduced values of real estate.
Among the recent introductions are the pinewood nematode from North America; Asian and Citrus longhorned beetles and ash dieback fungus from Asia; and sudden oak death and other Phytophthora species. (I described the extent of Phytophtphora infestations in European nurseries in a blog posted on April 25.) As a partial response, EU countries have created a network of nurseries intended to serve as an early warning system against further introductions of alien tree pests. (Descriptions of these pests and where they are found are available on the website of the European and Mediterranean Plant Pest Organization (EPPO) here)
ALB introduction sites in Europe
The European Union regulates invasive species through the Environment Directorate-General (DG Environment). However, tree-killing pests and other plant health concerns are the responsibility of a different governmental body, the Directorate-General Health and Food Safety (DG SANCO).
Maartje J. Klapwijk and colleagues note the risk associated with:
crates, pallets, and other forms of wood packaging;
wood chips (Europe imports more than 4 million tons of wood pellets as fuel in order to meet its carbon emission reduction goals) ; and
especially – living plants.
They note that the international community has adopted two international related sanitary agreements : ISPM#15 (wood packaging) and ISPM#36 (living plants). The European Union requires certificates stating that imported plants are free from harmful organisms and that phytosanitary measures stipulated by the importing country have been applied. However, limited resources mean that only a small proportion of living plants, plant material, soil and wood products arriving in Europe can be inspected. “The main purpose of the inspections is to verify whether shipments comply with regulations, rather than to stop potentially harmful organisms …” (my emphasis). Reflecting the differences in levels of concern among EU member states noted above, there are large differences in inspection intensity among the EU member states.
The pertinent European legislation is Directive 2000/29/EC. It relies on a ‘‘black-list’’ of plants and plant products that are banned from import and specifies procedures to apply when any of these banned products is found in the EU. According to Klapwijk and colleagues, these quarantine lists provide insufficient protection because harmful organisms that enter the EU often are unknown prior to establishment.
Aware of the current system’s inadequacies, the EC has proposed a new regulation which would simplify and harmonize plant passports, allow for stricter measures against pests, and address emerging risks from certain living plant imports from some non-EU countries. Instead of listing harmful plant pests, the proposed regulation “sets out the conceptual nature of quarantine pests” and empowers the Commission to adopt measures to control certain pests.
Klapwijk and colleagues praise these actions as a significant step forward. However, they note that the new rules still don’t provide for precautionary assessments of high-risk commodities. Nor do they restrict import of the highest-risk commodities, such as imports of large plants or plants in soil. (my emphasis)
The authors note that other countries take a more pro-active, precautionary stance. Australia and New Zealand require that all imported plant products be assessed and proved safe before import. The U.S. restricts the size of imported plants and does not allow imported plants to be in soil. (The U.S. has proposed a new approach that relies increasingly on integrated measures or systems approaches rather than port-of-entry inspection. However, this proposal has been pending for more than three years. (APHIS explains its proposal here)
The question is, do trade rules allow Europe to apply the same restrictions as other countries? As Klapwijk and colleagues note, the EU cannot adopt more rigorous phytosanitary measures without providing scientific evidence for this necessity. Preparing a risk assessment to make this case will involve considerable work. As part of this process, Europe should announce that it wishes to raise its “level of protection” and that more stringent phytosanitary measures are needed to achieve that new goal.
Meanwhile, the EU can enhance its active detection efforts and “rapid response” capabilities. The new EC directive will require countries in which a new pest is detected to eradicate or contain the pest. However, the response continues to depend on investments and actions by individual Member States – which have often been insufficient.
Klapwijk and colleagues endorse the suggestion by Hulme et al. (2009) that the European Commission establish a single agency to respond to introductions of any kind of invasive species (not just tree pests) – modeled on the European Centre for Disease Prevention and Control.
Finally, Klapwijk and colleagues note the importance of engaging the public. Citizens’ participation can enhance early detection and strengthen public support for management strategies.
CONCLUSIONS
We Americans are very lucky that the U.S. Department of Agriculture had fairly stringent rules governing plant imports before the World Trade Organization and SPS Agreement were negotiated in the 1990s. We don’t have the burden of proving that imports of large plants (small trees!) in soil is too risky. (This not to say that U.S. regulations should not be tightened further for the most high-risk imports. See Fading Forests III here). Europeans should be able to build their case for more restrictive trade rules on existing risk assessments and practices utilized by the U.S., Australia, New Zealand, and others; on the numerous studies published in recent years that describe recent introductions to Europe and the pathways by which they entered; and by the number of those introductions alone. (To see what has been introduced, visit the website of the European and Mediterranean Plant Pest Organization (EPPO) here)
One important step in improving U.S. rules would be to finalize the proposal – put forward in 2013 – to depend more on integrated measures or systems approaches rather than inspection at the port of entry. Join with me in urging the Secretary of Agriculture to finalize this proposal before he leaves office in January. Contact me via the “contact us” button on the webpage to learn how you can help.
The United Kingdom has voted to leave the European Union. This means that the U.K. has the opportunity – and burden – of developing its own phytosanitary regulations. The U.K. has some of the leading forest pathologists and entomologists. The risk is obvious to all – especially Phytophthora ramorum in larch plantations and ash dieback disease in many areas of the country. I hope that the British will seize this opportunity to adopt really effective phytosanitary regulations that can serve as a model for the rest of Europe – and possibly even the U.S.
Sources
Maartje J. Klapwijk, Anna J. M. Hopkins, Louise Eriksson, Maria Pettersson, Martin Schroeder,A°ke Lindelo¨w, Jonas Ro¨nnberg, E. Carina H. Keskitalo, Marc Kenis. 2016. Reducing the risk of invasive forest pests and pathogens: Combining legislation, targeted management and public awareness. Ambio 2016, 45(Suppl. 2):S223–S234 DOI 10.1007/s13280-015-0748-3
Hulme, P.E. 2009. Trade, transport and trouble: Managing invasive species pathways in an era of globalization. Journal of Applied Ecology 46:10-18
