Florida’s bromeliads: who will protect them?

Tillandsia utriculata; photo courtesy of Teresa Cooper

Florida has 16 native species of bromeliads. Up to 15 invertebrates depend on bromeliads, especially the water that collects at the bases of the leaves. See Frank (1983) and Frank and Fish (2008) for more information about bromeliads’ ecological importance.

Eight species had been listed as threatened or endangered in the state (visit here)  (Frank and Cave 2005) before arrival of the Mexican bromeliad weevil. The Florida Endangered Plant Advisory Council added two of its hosts – Tillandsia utriculata and Tillandsia fasciculata. The website now lists 12 species as threatened by the weevil.

Twelve species are believed to be vulnerable to the weevil. T. utriculata is at most immediate risk. Before arrival of the Mexican bromeliad weevil, some populations of this species were described by Teresa Cooper as “giant” and dense, containing very large mature plants and producing huge volumes of of seed.

One such population — in the Enchanted Forest Sanctuary in Brevard County – succumbed to the weevil quickly: 87% died in six months. At 27 months after arrival of the weevil, less than 3% of the original population remained. It is now rare to see large T. utriculata plants. Medium-sized plants put out inflorescences. The weevil persists at low levels, so is able to feed on and reproduce on medium and small plants. Several endemic wildlife species that inhabit the water pooled in T. utriculata’s base face global extinction (T.M. Cooper pers. comm. 2026).

damage to a bromeliad caused by the weevil; photo courtesy of Teresa Cooper

The first reason T. utriculata is at higher risk is that each plant can support many weevil larvae. Its leaves are softer (so more easily consumed) and its large stems contain lots of nutrients — for a bromeliad). More important is the plant’s very slow reproduction in contrast to the weevil’s rapid attack. T. utriculata plants do not produce seed until after they have grown for up to 20 years. Furthermore, an extremely small fraction of the ~ 10,000 seeds released by a mature plant make it to reproductive age. A plant that after 18 years begins growing an inflorescence — which then takes ~ a year to flower and produce seed – can be killed by a weevil within a few months. In addition, T. utriculata is monocarpic – it doesn’t produce offshoots. T.M. Cooper asserts that if the bromeliad weevil extirpates T. utriculata from Florida, it will not be because the weevil ate the very last plant, it will be because T. utriculata seed output has fallen below a sustainable level.

Teresa Cooper demonstrating the size of a T. utricuclata flower spike; photo courtesy of T. Cooper

A second host, Tillandsia fasciculata, had large and dense population in Loxahatchee National Wildlife Refuge (Palm Beach County) in 2002 to 2005. Almost every tree had multiple T. fasciculata plants; many were huge with multiple pups. When Teresa Cooper revisited about 10 years later, T. fasciculata plants were very sparse, large plants very rare; none was really large (T.M. Cooper pers. comm. 2026).

T. fasciculata is expected to decline more slowly than T. utriculata. First among several advantages is that its leaves are tougher and stems smaller, so they provide less nutrition to the weevil. Probably more important, T. fasciculata is polycarpic (it produces both seed and offshoots). A large T. fasciculata plant can sprout up to a dozen blooming rametes at a time. If the weevil kills one, other rametes will bloom and seed. At the same time, the plant might produce numerous up to 20 offshoots which come detatched from the “mother” plant and start a new individual. Still, as the weevil kills these rametes year after year the plant shrinks in size and eventually dies (T.M. Cooper pers. comm. 2026).

Teresa Cooper has documented damage on Tillandsia paucifolia, T. simulate, and T. variabilis (T.M. Cooper pers. comm. 2026). She has no funding to continue studying these species. I have been unable to find any more recent information about the status of the Tillandsia species. The Florida Department of Agriculture and Consumer Services does not have an active program addressing the weevil (Patrick Gordon, FDACS, pers. comm. June 2026).

There is considerably more information about another endangered bromeliad, Guzmania monostachia. This species has the broadest distribution of any species in the genus, stretching across northern South America, Central America, the Caribbean, as well as southern Florida. As the northernmost population, the Florida population might harbor unique genetics important for the species’ adaptation to climate change (Krupar et al. 2023).

Formerly more common, G. monostachia is now found in six fragmented and disjunct populations in five areas in Florida. The species has apparently been extirpated from four other sites by habitat loss, not depredations by the weevil. One set of habitats is in wetland sloughs on the peninsula’s west coast on the peninsula’s west coast. These forests comprise pond apple (Annona glabra) and Florida ash (Fraxinus caroliniana); Kupar et al. (2023) don’t mention whether this species is vulnerable to the emerald ash borer, which has not yet been detected in Florida. The largest of the bromeliad populations is in Fakahatchee Strand State Preserve, in Collier County in Southwest Florida. Fakahatchee Strand Preserve is Florida’ oldest and largest state park.  The bromeliad’s population was previously estimated to exceed two million individuals. Their number has been halved by weevil attack. Also, since M. callizona prefers larger plants, the proportion of reproductively mature individuals had been reduced from roughly 50% to only 10–20% by 2021. T.M. Cooper reports (pers. comm. 2026) fears this species might also be extirpated eventually.

Guzmania monostachia; photo courtesy of Teresa Cooper

The adjacent Big Cypress National Preserve is home to two populations of G. monostachia; they are separated by ~2,900 km2 so there is no interaction between them. The southern population consists of ~ 1000 individuals, the northern population comprises only~ 200 individuals.

Guzmania monostachia is in an even more precarious situation on the eastern side of the peninsula: tiny populations of two or three plants are found in three locations: Everglades National Park, Fuchs (formerly Sykes) Hammock Preserve, and Meissner Hammock Preserve.

The Mexican bromeliad weevil Metamasius callizona (Chevrolat) is native to southern Mexico, Guatamala, (Frank and Thomas 1994; Frank and Cave 2005) and Belize (Cooper, Cave and Frank 2023). Its presence in Florida was detected in a nursery in Ft. Lauderdale, Broward County, in 1989. Probably introduced on a shipment of ornamental bromeliads from Mexico. The nursery treated the infested plants, but the weevil had already established on native bromeliad species in the natural environment. By 1991, it was detected in four counties in southern Florida; by 1999, it was found in 12 more. It is now in most counties of peninsular Florida from Daytona (Volusa County) south to Miami-Dade (Patrick Gordon, Florida Department of Agriculture and Consumer Services, pers. comm. June 2026).

While chemical control is feasible in nurseries and display plantings, it can’t be used in natural areas, where the epiphytes are not accessible from the ground and stakeholders fear likely non-target effects.

Therefore, scientists initially focused on classical biocontrol. They made 16 expeditions to Mexico and Central and South America from 1992 to 2010 searching for natural enemies of the weevil. The chose parasitoid tachinid fly, Lixadmontia franki. A colony was established in the University of Florida’s quarantine laboratory and research on fly-weevil interactions was conducted for several years. Releases into the environment were begun under Federal and State permits in 2007. Although more than 3,100 flies were released, the species failed to establish. So this approach is no longer being pursued (Cooper, Cave, and Frank (2024); T.M. Cooper pers. comm. June 2026).

Meanwhile, in 2010, Dr. Frank and D. Giardina of the Florida Fish and Wildlife Conservation Commission observed that in one location in Belize the weevils had no apparent detrimental effect on bromeliads identified as Tillandsia utriculata (although there is some disagreement on this classification). Cooper, Cave, and Frank (2024) undertook a study to determine how the bromeliad could coexist with Metamasius callizona in Belize while being so vulnerable in Florida. They compared life cycle parameters (oviposition and pupation rates, egg hatch rate, adult emergence and size, and developmental time) of weevils from Florida and Belize. They also observed how populations of the weevil from Florida fared on three hosts: pineapple (Ananas comosus), T. utriculata collected from Florida, and T. utriculata collected from Belize. Finally, they quantified the hosts’ nutritional content using two measures (percent soluble solids and leaf toughness). 

Their most important finding is that weevil larva from Florida could not develop past the third instar on leaves of the T. utriculata from Belize. The weevil larvae starved because the Belize bromeliad’s leaves had fewer nutrients and were tougher than the leaves from T. utriculata collected in Florida.

bromeliads seen in Big Cypress National Preserve in the early 1980s; photo by F.T. Campbell

Based on this finding, Cooper, Cave, and Frank (2024) recommend that authorities introduce T. utriculata plants from Belize into Florida’s forests and allow them to colonize and/or hybridize naturally with Florida’s remaining plants. An alternative would be to breed hybrid Tillandsia in the lab and release them into Florida’s forests. I note that the American Chestnut Foundation pursued a similar strategy for decades to develop American chestnuts (Castanea dentata) able to tolerate the chestnut blight fungus (Cryphonectria parasitica).

Sources

Cave, R.D. 1997. Admontia sp., a potential biological control agent of Metamasius callizona. J Brom Soc. 47:244-249.

Cave, R.D. 2008. Biological control of the MEXICO bromeliad weevil. Biocontrol News and Information 29(1):1N-2N.

Cooper T.M. 2006. Ecological and demographic trends and patterns of Metamasius callizona (Chevrolat), an invasive bromeliad-eating weevil, and FLORIDA’s native bromeliads [Master’s thesis]. [Gainesville (FLORIDA)]: University of FLORIDA. 69 p.

Cooper, T.M., R.D. Cave, and J.H. Frank. 2023. Potential bottom-up control of Metamasius callizona in  Florida, USA. Entomologia Experimentales et Applicata. 2024. 172;4090421

Frank, JH. 1983. Bromeliad phytotelmata and their biota, especially mosquitoes. In: Frank J.H., Lounibos, L.P., editors. Phytotelmata: terrestrial plants as hosts for aquatic insect communities. Medford (NJ): Plexus. p. 101-128.

Frank, J.H. 1996. Bromeliad biota: history of Metamasius callizona FLORIDA [online]. Gainesville (FLORIDA): University of FLORIDA [cited 2010 Feb 1]. Available from https://www.entnemdept.uFlorida.edu/frank/bromeliadbiota/wvbrom6.htm

Frank, J.H. and R.D. Cave. 2005. Metamasius callizona is destroying FLORIDA’s native bromeliads. In: Hoddle MS, editor. USDA Forest Service Publication FHTET-2005-08. Vol 1. Second International Symposium on Biological

Control of Arthropods; 2005 Sep 12-16; Davos, Switzerland. Washington D.C.: USDA Forest Service. p. 91-101.

Frank, J.H. and D. Fish. 2008. Potential biodiversity loss in Florida bromeliad phytotelmata due to Metamasius callizona (Coleoptera: Dryophthoridae), an invasive species. Florida Entomol. 91(1):1-8.

Frank, J.H. and M.C. Thomas. 1994. Metamasius callizona (Chevrolat) (Coleoptera:Curculionidae), an immigrant pest, destroys bromeliads in FLORIDA. Can Entomol.126(1):673-682.

Krupar, S., A.A. Naranjo, G. Godden, N. Cellinese. The Fate of Guzmania monostachia in Florida Rests with Humans. Diversity 2023, 15, 525. https://doi.org/10.3390/d15040525

Potter, K.M., Escanferla, M.E., Jetton, R.M., Man, G., Crane, B.S., Prioritizing the conservation needs of US tree species: Evaluating vulnerability to forest insect and disease threats, Global Ecology and Conservation (2019), doi: https://doi.org/10.1016/

Salas, J. and J.H. Frank. 2001. Development of Metamasius callizona (Coleoptera:Curculionidae) on pineapple stems. Florida Entomol. 84(1):123-126.

Wood, D.M. and R.D. Cave. 2006. Description of a new genus and species of weevil parasitoid from Honduras (Diptera: Tachinidae). Florida Entomol. 89(2):239-24.

Posted by Faith Campbell

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

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

Or

https://fadingforests.org

Update on invasive plants in Hawai`i

Cibotium glaucum in Hawaii Volcanoes National Park; F.T. Campbell

A year ago I blogged about the status of Hawaiian species in the face of high levels of bioinvasions. I now update that discussion as it pertains to one of the invaders, the Australian tree fern Sphaeropteris cooperi.

S. cooperi has successfully invaded multiple regions, including the southern coast of South Africa, the Azores and Mascarene Archipelagos, and Hawai`i. The invasion’s impacts have been assessed only in Hawai`i. Studies found that the non-native tree ferns have outcompeted the dominant native tree fern Cibotium glaucum (Cibotiaceae), and altered leaf litter composition hence soil nutrient cycling. This in turn affects species assemblages (van den Berg et al. 2025).

Chau, Walker and Mehltreter (2013) documented the litter and soil chemistry in Hawaiian rainforests. They found that S. cooperi produces more leaves that grow faster, contain more nitrogen and phosphsorus, and decompose faster than the leaves of the dominant native tree fern C. glaucum. They compared the effect of leaf litter from the native and tree ferns on the growth and nutrient content of four native angiosperm species when they were grown in N-rich forest soil and P-rich landslide soil. The results suggested that nitrogen availability is the strongest driver of growth. The introduced tree fern, S. cooperi, can thus prompt more rapid growth of some native HI plants. They point out, however, that under natural conditions, native plants must compete for these additional nutrients with various non-native plants, including S. cooperi. The ultimate impact, then, remains unclear.

van den Berg et al. (2025) report that other invaded sites are at great risk Both the Garden Route region of South Africa and La Reunion Island in the Mascarene Archipelago in the eastern Indian Ocean have high bioidiversity. Both contain large, globally-recognized protected areas established to protect the native biodiversity: UNESCO Garden Route Biosphere Reserve and Reunion National Park. Despite their biological importance, both are among the top10 most invaded countries/territories globally (Tuberlin et al. 2017).

Sphaeropteris cooperi; photo via Easyscape

While climate change is expected to reduce the extent of suitable habitat for the Australian tree fern in both South Africa and La Reunion, the current situation is troubling. At present the tree fern occupies a narrower range of climatic conditions in both the Garden Route and especially on La Reunion than in Australia. (On La Reunion, 13.74 % of the fern’s apparent niche remains unoccupied.) van den Berg et al. (2025) are not sure what factors might be limiting the tree fern’s spread. They do urge educational campaigns to persuade people living near the Biodiversity Reserve to avoid planting the non-native tree fern.

The tree fern’s actual niche is somewhat uncertain because predation by deer (non-native to Australia) might have reduced its reproduction. The authors mention this but do not speculate further on the possible response of the fern to the absence of such stresses on La Reunion.

SOURCES

Chau, M.M., Walker, L.R. and Mehltreter, K. An invasive tree fern alters soil and plant nutrient dynamics in Hawaii. Biol Invasions 15, 355–370 (2013). https://doi.org/10.1007/s10530-012-0291-0

Turbelin,A.J., Malamud,B.D., Francis,R.A. 2017. Mapping the global state of invasive alien species: patterns of invasion and policy responses. Glob. Ecol. Biogeogr. 26,78–92. https://doi.org/10.1111/geb.12517.

van den Berg, M.L., G. Singh, E.J. McCulloch-Jones, M. Rouget, D.M. Richardson, T.B. Robinson. 2025. The invaded range of the tree fern Sphaeropteris cooperi is predicted to shrink in two southern hemisphere biodiversity hotspots. African Journal of Botany 178 (2025) 390-399

Posted by Faith Campbell

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

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

Or

https://fadingforests.org

Invasive species on the African Continent

We are beginning to get more information about invasive species on the African continent.

a flyer naming principal invasive ornamental plants in Kruger National Park

In several countries, the focus has been on threats to agriculture. Previous blog about horizon-scanning in Ghana. In Zimbabwe, N. Mudada and colleagues (2026; full citation and the end of this blog) found alarming, if not surprising, levels of risk to food production from introduced invasive plants. They investigated 1,668 human-aided transboundary plant introductions at 14 ports of entry and non-official crossing points over the course of four years.

They estimate that the 20,000 trucks that transported maize into the country over the four years carried over 20,700 metric tons of weed seeds and rubbish! They recorded detections of 11 species in eight orders. The pathways are familiar. As noted, several weeds were contaminants of grain shipments; Convolvulus arvensis in wheat for human consumption, Helianthus annus and Datura stramonium in maize for animal feed. Adenium obesum and Vitex agnus-castus were being smuggled for planting as flowers and ornamentals. (Vitex agnus-castus was also smuggled in passenger baggage for its medicinal properties). Several Lemna species (an aquatic plant) were also smuggled for planting as animal feeds.

In some cases, the focus is the threat to native ecosystems. I posted a blog the about threat of an introduced pathogen to trees in the remnant rain forests of Madagascar.

South Africa still has the lead in addressing invasive species. Regarding invasive plants specifically, the country has the benefit of more than 150 years of botanizing. The richness of the region’s flora is globally recognized. South Africa also has a long history of studying and managing invasive species, especially plants.

South African scientists and colleagues in Botswana, Eswatini, Lesotho, and Namibia have published four editions of the Flora of the Southern Africa region since 1984. In 2006, the PRECIS database of the South African National Biological Diversity Institute (SANBI) was combined with the Tropical African Plant Checklist published by the Conservatory and Botanical Garden of Geneva to create the African Plant Checklist and Database Project. It is continually updated. This is the first continental flora checklist for Africa; it fulfils countries’ obligations under the Convention on Biological Diversity’s Global Strategy for Plant Conservation.

For South Africa specifically, scientists have produced a national plant checklist that is updated annually.

The 2025 Checklist reports that 21,539 plant species are extant outside cultivation in the country; these comprise 20,204 indigenous species and 1,329 naturalized species. Thus, 6% of the total flora is non-indigenous. Of these, 649 (48.8% of the non-indigenous species, 3% of all plants) of them are invasive.

[Naturalized species are defined as species whose documented natural range does not include South Africa, but have overcome a biogeographic barrier and now sustain self-replacing populations for two or more life cycles or over a given period of time in the country. These populations are maintained without direct intervention by people, or despite human intervention. Invasive species meet the above definition plus produce reproductive offspring, often in large #s at considerable distances from the parent and/or site of introduction, and have the potential to spread over long distances.]

Since the previous checklist was published in 2006, botanists have identified 1,048 additional species – a 4.9% increase. Eighty-two percent of the newly identified species (865 species) are “naturalized”. Specifically, 414 new species are categorized as naturalized (a 31.1% increase), and 451 new species are classified as invasive (a whopping 69.5% increase). Le Roux and Klopper attribute these steep increases to active botanizing by SANBI’s Invasive Species Programme (begun in 2008), and the Southern African Plant Invaders Atlas Project (begun in 2010).

Of the 384 plant families present in South Africa, 350 contain at least some indigenous species. Thirty-four families contain only naturalized species. Among the 2,189 plant genera present, 459 (21%) contain only species that are non-indigenous.

Three families stand out because of the particularly high numbers of naturalized species: Fabaceae (143 species; 11% of all naturalized species), Asteraceae (140 species; 10%), Poaceae (123 species; 9%). Two of these families — Asteraceae and Fabaceae — are also the largest families among native South African plants. The third, grasses (Poaceae), ranks seventh in the list of most specious families indigenous to South Africa. The next group of families with high numbers of naturalized species has less than half as many invasive species: Myrtacae (55), Amaranthacea (52), Solanaceae (48). None of these families ranked within the top 20 families of indigenous plant species.

The genera with the most naturalized species were Solanum, Euphorbia and Acacia (all 24 or 23 species).

Acacia cyclops; photo by David M. Richardson

South African scientists are also exploring how to balance conflicting goals and perspectives when an invasive plant species has economic or social value. The example chosen by Mbobo et al. (2025) is guava (Psidium guajava) – a nutritious and popular tropical fruit grown commercially in South Africa, but also invasive along roadsides, watercourses and forest margins. Invasions are especially common in eastern parts of country; large monocultures are found in KwaZulu-Natal. Outbreaks have also been detected at five sites in Western Cape in riparian zones and at a hot spring. Mbobo et al. (2025) note that the microclimatic conditions at this last location differ from the broader conditions in the region – which are what most models would measure.

The scientists used models to predict where guava might invade – especially in large monocultures – and compared those areas to where the tree can be grown in cultivation with human inputs, e.g., irrigation. They then assessed whether six regulatory approaches would avoid restricting guava farming in areas at minimal or low risk while still protecting vulnerable locations. They also considered the amount of information required to implement the approach and costs of acquiring the information; and level of likely public acceptance. Mbobo et al. (2025) laid out the trade-offs between continuing to regulate planting of the species at the provincial level vs. at the municipal level. Prohibiting planting of guava in provinces where it is recorded as invasive allows some plantings near natural forests and riparian areas that are highly susceptible to guava invasions. On the other hand, nearly half of the prohibited area is outside the known or likely at-risk area. The provinces do allow exceptions through a permit process. Adopting more geographically limited rules by regulating at the municipal level would enable a tighter link to geographic areas at highest risk. However, this approach does not address long-distance seed dispersal by animals. Furthermore, the very detailed regulations might confuse stakeholders and complicate enforcement. Also, the models lack sufficiently fine spatial resolutions to predict invasible areas so accurately. Finally, the reduction in regulated area is minimal (~ 14%), so the economic benefits are unlikely to outweigh the significantly higher administrative costs and risk of allowing guava invasions in new sites.

Guava fruit on tree; Roenashy via Wikimedia

Gildenhuys et al. (2026) analyzed the factors that drive which non-native plants establish where. They assessed the roles of temperature, precipitation, urbanization intensity, urban area, travel time, year of city’s establishment, and human population density in determining which plant species are present in 54 urban centers in Western Cape Province. The cities have significant differences in climate: Mediterranean in the far southwest, warm temperate in the southeast, and semi-arid towards the interior. The expectation was that these drivers and assembly processes are influential at more advanced invasion stages when the species have already overcome some barriers to dispersal, so are now found in reasonably suitable habitats.

Gildenhuys et al. (2026) found temperature and precipitation were most important in determining plant species’ presence. This was especially true at the boundary between arid and mesic climates. These strong environmental gradients are the same ones which have driven high differences in native species presence across the province. [See pamphlet describing invasive plants in Cape Town.] This finding supports the “Goldilocks hypothesis”: that non-native plant species assemblages are driven by the same abiotic variables as native species assemblages. While did not directly study the “Biome decides hypothesis” (the composition of non-native flora is mediated by the biotic effects of native flora and fauna), Gildenhuys et al. (2026) doubt its applicability here because native species’ presence has probably been greatly reduced by the effects of urbanization.

Urbanisation intensity itself ranked third as a factor. Its effect was strongest at low to medium urbanization intensities. Because urbanization creates novel habitats, such as, “hardscapes” of paved surfaces that resemble deserts, their non-native plant assemblages are dominated by similar, urban specialist, species. At lower urbanization intensities a greater variety of habitats is available. Gildenhuys et al. (2026) conclude that urbanization acts primarily as a driver of opportunistic habitats for species at later invasion stages rather than as a filter of species introduction.

An earlier study found a similar effect from road density (often associated w/ urbanization) as an explanation for where specific woody non-native species establish. They do concede that larger urban areas might experience greater propagule pressure.

Gildenhuys et al. (2026) note that recent globalization of the plant trade has probably changed the specis planted in urban centers. For example, cities in the Western Cape are increasingly replacing English oak (Quercus robur) with more disease-resistant oaks. The change might reflect greater environmental awareness and regulations issued under the National Environmental Management: Biodiversity Act 10 of 2004. In newly established urban centers, fewer invasive species are being planted — at least among trees.

SOURCES

Gildenhuys, C.P., L.J. Potgieter, C. Hui, D.M. Richardson. 2026. Drivers of compositional turnover of the NIS urban flora in the W Cape, South Africa. Urban Ecosystems (2026) 29:51 https://doi.org/10.1007/s11252-026-01919-3

Le Roux, M.M., R.R. Klopper. 2025. Taking stock of South Africa’s flora. South African Journal of Botany 184 (2025) 571-579

Mbobo, T., D.M. Richardson, A. Datta, K.T. Faulkner, J.R.U. 2025. Wilson. Spatially-Differentiated Reg of NIS Can Be Improved Using Spp Distribution Models: Psidium guajava in South Africa as a Case Study. Diversity and Distributions. 2025 31:e70102 https://doi.org/10.1111/ddi.70102

Mudada, N., J. Chitamba, E. Nyangani, C. Chapano, N. Mapope,and W. Ngezimana. 2026. Weeds associated with cross border traffic, their approach and infestation rates in Zimbabwe.  ISABB Journal of Food and Agricultural Sciences. Vol. 12(1) January-June 2026. DOI: 10.5897/ISABB-JFAS2025.0192

Posted by Faith Campbell

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

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

Or

https://fadingforests.org

Floral richness of South Africa

Cape Coast lily (Crinum macowanii); photo by Jaqui Geux

South Africa is rich in plant diversity. That diversity is strongly shaped by the country’s varied topography, soils, & climate. Nine biomes & 465 vegetation types are recognized in a country of just 1.2 million km2 (471,445 square miles).

There is a long history of botanizing in southern Africa – with impressive results that include a Flora of the Southern Africa region (it covers Botswana, Eswatini, Lesotho, Namibia, as well as South Africa) and the African Plant Checklist & Database Project, which is the first continental checklist for Africa. This publication – which is being maintained continuously – contributes to goals of the Convention on Biological Diversity’s Global Strategy for Plant Conservation.

South Africans have also produced a national plant checklist that is updated every year. The most recent Checklist dates from 2025. The checklist includes bryophytes (mosses, hornworts, & liverworts), lycophytes & pteridophytes, gymnosperms, & angiosperms. Compilers plan to include marine macro-algae in future.

The 2025 checklist names 21,539 species in South Africa – 20,204 indigenous species, 1,329 naturalised species. Based on the, South Africa’s national flora comprises 5.3 % of the estimated ~ 380,000 plant species on Earth.

Geissoloma marginatum; photo by Tony Rebelo via Wikimedia

South Africa is home to 384 plant families, of which all but 34 contain only indigenous species. All the species in seven families are endemic to South Africa. These families are Bruniaceae, Geissolomataceae, Grubbiaceae, Lanariaceae, Penaeaceae (excl. Oliniaceae), Rhynchocalycaceae, & Roridulaceae. Of the 2,654 genera, 2,189 are indigenous. Three hundred (12%) of these genera are endemic. Sixty percent of the 20,204 indigenous species are endemic. All the endemic families other than Bruniaceae are composed of a single genus – demonstrating the phylogenetic uniqueness of this flora.

The 2025 Checklist contains 1,048 species that did not appear in the previous checklist (published in 2006). This is an increase of 4.9%. Numbers of indigenous taxa increased by less than 5%: additional 623 indigenous species (3.1%); 520 endemic species (4.3%). Numbers of non-indigenous species increased by considerably higher proportions: naturalized species increased by 414 species (31.1%), & invasive species by 451 (69.5%). These 865 species constitute 82.5% of all 1,048 newly recorded species. (I report the findings on non-indigenous species in a separate blog.)

The detection of previously unidentified species and infraspecific taxa – both native and non-indigenous – is the result of systemic botanizing campaigns focused on particular families. Thus, a study of the family Iridaceae in southern Africa led to description of 169 species in 20 genera. More than two decades of work on the Pelargonium (Geraniaceae) resulted in recognition of 34 new taxa. Thirty-three new species have been described in the genus Indigofera (Fabaceae).

The most specious plant family indigenous to South Africa is Asteraceae, with 2,124 species. Aizoaceae & Fabaceae follow with 1,603 & 1,566 species, respectively. The newly expanded Iridaceae is fourth; it encompasses 1,189 species. The world-famous Proteaceae rank 13th, with only 355 species. Considering genera, the largest by far is Erica (heath) at 734 species; no other genus houses more than 300 species. [The famous orchid genus Disa ranks 18th. There are ~182 species on the continent, primarily in East & Southern Africa.]

Disa uniflora on Table Mountain; F.T. Campbell

When considering phylogenies with high levels of endemism, the leading families are – again — Aizoaceae (1,426) and Asteraceae (1,352). Ranked third is Iridaceae (983). Fabaceae is ranked 4th (961). Nearly half (49%) of species in 1,071 genera are endemic. Again Erica ranks highest: 581 species – 78% of the species in the genus – are endemic. This is double the number in the genus ranked second — Aspalanthus (261species; all but 34 species are endemic). Pelargonium is 3rd : 204 of 261 species are endemic.

Flora of the provinces

 Of South Africa’s nine provinces, KwaZulu-Natal (94,361 km2) is home to the greatest diversity in terms of plant families (331 families) and genera (1,718 genera). Neighboring Eastern Cape Province (168,966 km2) ranks second with 305 families and 1,576 genera. Western Cape has somewhat fewer plant families (294) and genera (1,475), but by far the most species (11,379). Western Cape also leads in the proportion of its plant taxa that are endemic to the province: 58%. (This reflects the presence of a globally recognized distinct flora, the Cape Floral Kingdom.) KwaZulu-Natal and Eastern Cape (16% endemic) share most of their plant taxa with neighboring provinces or countries – Mozambique. Therefore, their levels of endemism are only 8% and 16%, respectively.

The clustering plant diversity and endemism in the south & east reflects the topographic variation provided by the Escarpment of South Africa.

The largest province is Northern Cape Province at 372,889 km2. It is home to 5,058 species but its fairly uniform terrain means there is not very high species diversity (25 % – half the proportion in Western Cape). However, the flora is unique because adapted to the harsh environment (I concede these statements seem contradictory).

Pachypodium namaquanam; F.T. Campbell

SOURCE

Le Roux, M.M., R.R. Klopper. 2025. Taking stock of South Africa’s flora. South African Journal of Botany 184 (2025) 571-579

Posted by Faith Campbell

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

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

Or

https://fadingforests.org

EAB infestation at 20 years: focus on green & white ash & white fringetree

dying ash in Shenandoah National Park; photo by F.T. Campbell

The emerald ash borer (Agrilus plannipennis; EAB) was detected in North America in 2002. So both U.S. and Canadians have been motivated to evaluate the probable trajectory of the primary hosts – the ash genus Fraxinus – in the face of the ongoing invasion. See Deschênes et al. 2026 and Wilson et al. 2025 – full citations at the end of this blog. Both studies focused on white (Fraxinus americana) and green ash (F. pennsylvanica); they say next to nothing about black ash (F. nigra). I regret this silence because of the unique ecology of black ash swamps. Neither addresses the threat to Oregon ash (F. latifolia) in the West.

The two assessments have similar findings: high mortality of larger trees (canopy and “recruit” size trees); abundant regeneration (seedling and saplings sizes) after an initial period; and uncertainty as to whether persisting EAB populations will kill the saplings before sufficient numbers grow into reproductive size.

There are two conspicuous differences. First, the American study does not consider the possible impact of biological control – although USDA APHIS has placed all its effort on this approach since January 2021. The Canadians report that self-sustaining populations of the wasps are now found across the northern U.S. and eastern Canada. In their study, conducted in Ontario, they detected only Tetrasticus planipennisi; it was parasitizing 16% of the EAB larvae in dissected stems. This wasp’s affinity for colder climates and short ovipositor – which limits it to parasitizing larvae inhabiting small stems – are portrayed as positive traits under these circumstances.

Second, the Canadians did not find “lingering” adult ash trees as have the Americans. These trees indicate the probability of finding workable levels of genetic resistance to the EAB. USDA Forest Service scientists are pursuing a breeding program.  While in south-central Michigan, where overstory ash mortality typically exceeded 80%, 46% of overstory ash and 82% of ash recruits were relatively healthy (Wilson et al. 2025), in Ontario none of 1,129 overstory ash trees survived beyond seven years after EAB detected. No trees exceeded 15 cm dbh (Deschênes et al. 2026).

ash resistance breeding trial at Holden Arboretum; photo courtesy of Jennifer Koch, USFS

Regeneration

As Deschênes et al. (2026) state, the future of ash stands depends on the complex of interactions among environmental conditions, management interventions, efficacy of natural enemies (natural or introduced), and life-history traits of the insect and its host. Coexistence might be possible if EAB larval densities remain sufficiently low to support survival of residual trees and successful seedling recruitment.

Larval densities in Ontario were said to be generally low, suggesting reduced carrying capacity in post-invasion forests, lower EAB fecundity, and higher EAB mortality in regenerating stems. Deschênes et al. (2026) note that in more northern areas colder temperatures are thought to slow larvae development. Perhaps these larvae might also be less vigorous, so they night disperse only over short distances. Still, there were sufficient EAB present after all the overstory trees had died to create 97% of the 298 galleries in regenerating ash stems (Deschênes et al. 2026). Furthermore, Wilson et al. (2025) say that EAB densities in infested trees in Michigan were similar to densities recorded during the initial invasion. This seems ominous to me – a solid foundation from which beetle populations could build up again as regenerating ash grow and provide more phloem for the insect to exploit.

Ash reproduce by both flowering/seeding and sprouting from the base. EAB predation is not the only complication. First, ash are dioecious so mature trees of both sexes must grow within a few hundred meters. Second, predation by the ash seed weevil (Lignyoodes helvolus) reduces seed supplies. Dense sedge mats can prevent germination (Wilson et al. 2025). Scientists generally believe that the soil seed bank is quickly exhausted, although Wilson et al. (2025) cite others’ conflicting findings. Neither article discusses predation by mammals, e.g., deer or rabbits. Wilson et al. (2025) mention attacks by beavers.

ash saplings felled by beavers; photo by F.T. Campbell

Wilson et al. (2025) did not study whether stump-sprouted ash were able to successfully recruit into the overstory. They do report that in one study in southeastern Michigan stump sprouts were the dominant form of green ash regeneration and about a quarter of these sprouts produced seeds at least once. Deschênes et al. (2026) found that on average 47% of regenerating stems at their Ontario research sites originated from stump sprouts.

EAB has been documented to attack and kill trees when the main stem is as small as 2.5 cm. While EAB probably prefer larger stems, Deschênes et al. (2026) suggest that stems become acceptable at the lower range of size required for seed production – 8–10 cm dbh. Reliable and abundant seed production doesn’t occur until white or green ash achieve > 20 cm dbh. At their Ontario sites, Deschênes et al. (2026) found that 42% of regenerating stems has been infested by EAB at least once; 14% had been attacked five or more times. They removed 74 EAB larvae from 28 stems; 49 (66%) were alive. Fifteen EAB (16% of current year galleries) had been parasitized — all by Tetrastichus planipennisi. They also observed numerous signs of defensive responses.

In Michigan, no ash recruits — living or dead – were found in plots in 28% of the cells. In the remaining 128 cells, an average of ~33% of ash recruits were infested by EAB, and ~21.4% of ash recruits dead. As is typical, white ash fared better than green ash. Recruit sized ash trees were twice as likely to die than to survive and mature into overstory size (Wilson et al. (2025).

In Ontario, as noted, all canopy ash had died. There were 119 live trees 5 – 10 cm dbh – a tenth as many “mature” ash as when EAB arrived, and all were smaller. There was abundant regeneration in most sites initially, but at the longest-infested sites in Essex County, regenerating ash stems were half as numerous as early after the transition (Deschênes et al. 2026).

The Canadians found it encouraging that some of the regenerating stems were vigorous despite containing EAB gallery densities greater than 20 larvae·m?2 of phloem. They did not know the mechanisms underlying survival of these stems. Possible explanations ranged from the low EAB carrying capacity of smaller trees to stronger host defenses in regenerating stems to EAB mortality due to parasitism.

Wilson et al. (2025) note that despite more than 20 years of EAB presence, densities of ash recruits, saplings, and seedlings were high relative to other species. However, they remind us, ~ one-third of the live ash recruits were infested so their survival into reproductive size was uncertain. The high mortality of overstory ash results in loss of seed resources, greater sun exposure, and cascading consequences for forest composition and function. In upland sites, cells with low ash basal area favored Quercus rubra and Tilia americana. They conclude that changes to forest composition is probably site specific — largely depend on what tree species are already present.

Despite the challenges described above, the Canadian scientists also believe that these findings demonstrate that ash has a capacity for long-term regeneration (Deschênes et al. 2026).

Changing Species Composition in the U.S.  (Wilson et al. 2025)

Canopy gaps caused by ash mortality have largely been filled by lateral ingrowth of species already there — American elm (Ulmus americana), black cherry (Prunus serotina), and northern red oak (Quercus rubra). The regeneration strata (saplings and seedlings) is dominated by Fraxinus (white outnumbering green when differentiated), maples (Acer rubrum, A. saccharum), black cherry, Crataegus species and Carya ovata. Elms are consistently among most common non-ash taxa among overstory, recruit, sapling and seedling strata. At some Ohio sites there was also increased abundance of non-native tree and shrub seedlings. This is not surprising since invasive plants are widespread in the forests of Ohio and other eastern states. A decade ago 93% of Forest Inventory and Analysis (FIA) plots in Ohio had at least one of 50 invasive plant species.

In another paragraph they mention Tilia americana as one of the important species in these forests.

Situation in Canada (Deschênes et al. 2026)

Deschênes et al. (2026) express concern that the death of nearly all canopy-level trees will substantially reduce ash’ ability to fulfill its ecological roles in these ecosystems. Still, ash regeneration is persisting for decades following overstory mortality. The taxon’s continued presence is driven largely by strong sprouting, which has been observed in several locations in Ontario. In some areas, low EAB infestation rates and evidence that regenerating stems can withstand multiple infestations raises hope that some might reach maturity and produce seeds. This scenario would be similar to that of elms, in which surviving trees contribute to ongoing regeneration and might eventually facilitate development of some level of resistance to the invasive fungus. A second possibility is that ash’ high sprouting capacity might point to a scenario similar to that of American chestnut. This species has persisted for a century primarily as sprouting shrubs — although they rarely reach reproductive maturity.

white fringetree; photo by Ryan Somma via Wikimedia

White Fringetree

Scientists also reviewed the status of a secondary host of EAB in North America, white fringetree (Chionanthus virginicus). Earlier studies of this host-pest relationship had been conducted on ornamental plantings where the trees tend to be scattered across open lawns and actively managed – including protection from pests. The Cipollinis (see full citation at the end of this blog) believe they might be better able to ward of EAB attack than are wild, unmanaged trees in forests that must compete for resources. They wanted to assess the current status and likely trajectory of the tree species in the wild.

To do so they revisited a wild population of the tree in southern Ohio previously assessed 10 years earlier. White fringetree is a small multi-stemmed tree native to the southeastern U.S. It is widely planted as an ornamental in across the east. In Ohio, white fringetree grows wild in only a few southern counties, in small populations or as widely scattered individuals. The species is classified as “Potentially Threatened” at the state level.

In 2015, 30% of the white fringetrees at the site were infested. These trees had signs of stress but none had died. EAB larvae grow more slowly on fringetree than on North American ash species. Meanwhile, all mature white ash trees at the site had been killed by EAB. Smaller white ash trees more comparable in size to the white fringetrees had attack rates and impacts comparable to those on the fringetrees.

In their new study, the Cipollinis found that nine of 31 trees tagged in 2015 (29%) had died; 22 (71%) were alive. Of those 22 living trees, 12 (55%) stayed the same or improved slightly over the five-year period; 10 (45%) declined. Five of these 22 living trees (23%) had evidence of current infestation. Trees that had died had a higher incidence of old EAB galleries, adult exit holes, and woodpecker activity. This is interpreted as demonstrating that EAB must cause extensive damage to kill fringetrees.

In summary, fringetrees in a wild unmanaged population continued to be attacked by EAB over 10 years and suffered higher attack rates and more significant impacts than those previously observed in managed pops. The Cipollinis conclude that trees large enough to attract EAB oviposition will continue to decline in health and be killed as long as beetles are present. They expect that wild white fringetrees might meet the same fate as ash trees, but over longer time scales. 

At the same time, this delay in complete mortality might create a refugium for remnant populations of EAB after most ash have been killed. This status would be exacerbated if it turns out that the biocontrol agents cannot find their target — EAB — in the alternative host. The Cipollinis found lower parasitism rates by Tetrastichus planipennisi in fringetrees, although this was not true for the egg parasite Oobius agrili and two Spathius larval parasites.

Whitebark fringetree populations can produce few adult EAB because the trees are small and contain low amounts of phloem. Still, as young trees grow into vulnerable sizes they might help sustain the EAB population – as young ash trees in the area appear to do.

While caution is appropriate in interpreting findings from a study of a single population, the Cipollinis argue that this population has been studied intensively: assessed six times over 10 years, beginning at the start of the EAB infestation. Therefore they think their analysis provides useful informative regarding the long-term impacts of EAB on fringetree.

They concede that larger populations in areas deep within the tree’s native range might experience different dynamics and impacts. So far, however, observations in Chattahoochee National Forest in Georgia and at Great Falls Park on the Maryland-Virginia border generally support their finding that wild fringetrees in natural landscapes will suffer higher attack rates and be more severely impacted by EAB than trees in managed landscapes.

Finally, the Cipollinis fear that a close relative, pygmy fringetree, Chionanthus pygmaeus, is at particularly high risk because it is endemic to only a few counties in the sandhills of central Florida. The species is already classified as endangered by both the state and the federal governments. The pygmy fringetree is smaller than white fringetree, so its size might help it escape attack. However, adults achieve sizes comparable to that of fringetree in some cases. So when EAB reaches Florida, the specie appears to be highly vulnerable.

SOURCES

Cipollini, D. and K. Cipollini. 2026  The Fate of a Wild White Fringetree (Chionanthus virginicus) Population in Ohio 10 Years After Invasion by Emerald Ash Borer (Agrilus planipennis) Forests 2026, 17, 712

Deschênes, É., C.J.K. MacQuarrie, L. Scott, C. Zimmerman, and I. Aubin. 2026. Ash population dynamics after two decades of emerald ash borer infestations in Canada. Canadian Journal of Forest Research. Can. J. For.Res. 56: 1–13 (2026) | dx.doi.org/10.1139/cjfr-2026-0075

Wilson, C.J, L. Labbate, T.R. Petrice, T.M. Poland, D.G. McCullough. 2025. Ongoing regeneration of ash and co-occurring species 20 years following invasion by emerald ash borer. Forest Ecology and Management 580 (2025) 122546

 

Posted by Faith Campbell

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

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

  Or

https://fadingforests.org

Factoids from recent publications

Agrilus auroguttatus

Agrilus genus

Hernández‐Gutiérrez, Nichols, and Kelly (2026) (full citation at the end of the blog) analyzed interactions between this genus of beetles and oaks (Quercus species). In this context, they report that 32 Agrilus species from Africa, Asia, Europe, and North and South America use 51 Quercus species as hosts in their native range. Eighteen (56.25%) use only Quercus hosts.

Oaks that host Agrilus species cluster in several clades, i.e., the entire Section Cerris and one clade of Section Ilex and two clades of section Lobatae. Clades where Agrilus hosts are underrepresented are Sections Cyclobalanopsis and Quercus &, surprisingly, two clades in Section Lobatae.  

Their analysis indicated that beetle-oak interactions involving all the 32 Agrilus species and 105 Quercus species in their study had a significant likelihood of being damaging. For example, northern red oak (Q. rubra) is already known to host six Agrilus species. Hernández‐Gutiérrez, Nichols, and Kelly (2026)’s analysis indicated that this tree species might be utilized by all 32 Agrilus species assessed. The tree’s wide distribution (both native and introduced) places it close to other known or probable hosts, which exacerbates the risk of an interaction. Another 26 Quercus species are predicted to host ten or more Agrilus species.

The model was not successful in predicting hosts of A. auroguttatus (goldspotted oakborer) in its introduced range in California.

black oak (Quercus kelloggii) in Cleveland National Forest killed by GSOB; photo by F.T. Campbell

It also predicted that few of China’s oak species might host Agrilus beetles. However, as Dr. Robert Haack notes (pers. comm. June 2026), larval hosts have been identified for only 13% of the nearly 1,200 Asian Agrilus.

Some Agrilus species have a very large number of predicted novel interactions. A. graminis and A. angustulus are predicted to have more than 40 novel oak hosts. Both have numerous known oak hosts; so their “polyphagous” nature is already documented.

Since two-thirds of 666 Agrilus species with known larval hosts exploit only one plant genus as a host in their native range, Hernández‐Gutiérrez, Nichols, and Kelly (2026) assert that they might spread faster if introduced to homogeneous rather than species-rich habitats. Dr. Haack believes that this statement is too broad (pers. comm. June 2026).

A. bilineatus; photo by Christina Butler via Wikimedia

Twolined chestnut borer

Haack and Blank (2024) document that the twolined chestnut borer, Agrilus bilineatus has preferentially infested apparently healthy English oak (Quercus robur) trees over healthy native oak trees in Michigan. In North America, A. bilineatus is a major pest of oaks and American chestnut (Castanea dentata)when they are stressed by drought or other factors. Infestation typically begins in the upper crown and proceeds downward; tree death often occurs within three years.

 At several sites in southern Michigan, where English oaks were intermixed with native white oaks (Quercus alba) and close to northern red oaks (Quercus rubra), A. bilineatus preferentially infested Q. robur trees that initially appeared healthy. Further study revealed that many of the English oaks attacked had low or depleted root starch levels.

Although these findings are cause for alarm, English oak is already used by 11 species of Agrilus in Europe. Perhaps the tree and ecosystem might have sufficient defenses in Europe. Meanwhile, A. bilineatus has been reported in Turkey as of 2018; I have found no recent information about the damage whether it is causing any damage there.

Data from Britain and Worldwide

Peyton et al. (2026) reviewed the effectiveness of a “horizon scanning” exercise conducted for Great Britain (England, Scotland and Wales). They report that 3,248 recognized non-native species have been detected in Great Britain, of which 2,016 have established self-sustaining populations. Some 194 (~10%) are considered invasive, that is, have negative impacts on biodiversity and wider ecosystem viability. These consist of 108 terrestrial species, 47 freshwater species, and 39 marine species. These bioinvaders cost the British economy an estimated ~£3.9 billion per year (the bulk of the damage is attributed to ash dieback, caused by the fungus Hymenoscyphus fraxineus).

In the decade between completion of the “horizon scan” and the present, 143 species were recorded as being introduced. The horizon scan predicted 31 of these species, 22%. Peyton et al. (2026) consider this to be success.

Peyton et al. (2026) report that globally, ~ 6% of non-native plant species are ranked as invasive. Among invertebrates, this proportion rises to 22%. Considering vertebrates introduced to Europe or North America, the figure is more than 50%!! I welcome global data that support my call for rethinking the “rule of tens” long relied on for estimating the proportion of non-native species that are invasive.  

Discussing bioinvaders’ role in causing extinctions, Peyton et al. (2026) report that 30 predators have been linked to declines and extinctions of 738 vertebrate species.

Peyton et al. (2026) also discuss the difficulty in predicting an introduced species’ impacts when in some cases the time lag between introduction and presence in the wild or between establishment and spread w/in the region can last decades or even a century. They cite as an example Senecio squalidus, which escaped the Oxford Botanic Gardens in the 1700s but started to spread only during mid-1900s.

Australia

More than 300 non-native insect pests, pathogens and nematodes have established on tree or shrub hosts in Australia; 20% have caused moderate to high impacts to commercial plantations, urban forests, or trees in natural ecosystems (Carnegie et al. 2026).The rate at which non-native forest pests and pathogens have been detected in Australia has doubled since 2018 compared to earlier decades: from ~ 1.5 to ~ 3 per year. Carnegie et al. (2026) attribute this rise to greatly expanded official surveillance efforts. Still, three-quarters of the most recent detections came too late for eradication to be attempted.

The Forestwatch program (inaugurated – under a different name – in 2022) includes pathogens. I rejoice!!! Still, the target species threaten primarily tree species not native to Australia but important to commercial forestry or urban forests: Asian longhorned beetle,  burnt pine longicorn (Arhopalus ferus), pine pitch canker, pine wilt disease, red turpentine beetle (Dendroctonus valens), Asian spongy moth, red needle cast, and sudden oak death. The exceptions are strains of Austropuccinia psidii not yet intro to Australia, and eucalypt leaf blight (caused by Teratosphaeria destructans) (Carnegie et al. 2026).

Austropuccinia psidii infection on Melaleuca in Australia; photo by John Tann via Flickr

Among the introduced pests causing the greatest damage to native species are

  • Phytophthora cinnamomi: this soil fungus can kill 40% of the plant species in the southern portion of Western Australia  – which is one of 36 “Biodiversity Hotspots” recognized by the Critical Ecosystem Partnership Fund.  
  • Austropuccinia psidii (cause of myrtle rust) in natural ecosystems; Members of the host family Myrtaceae occur in 11 of 13 major vegetation formations on Australia. Various authorities have identified 76 species as at risk to the rust.

I hope the Australians are developing strategies for landowners to counter damage by the polyphagous shot hole borer (Euwallacea fornicatus) and its associated fungus (Fusarium euwallaceae). DMF Outbreak detected near Perth, Western Australia, in 2021 – apparently three years after the actual introduction. By June 2025 authorities had determined that it was too widespread to be eradicated, so landowners will be responsible for any management.  (Carnegie et al. 2026) Impact is predicted to be greatest in urban landscapes, and cost up to AU$9.7 M per annum to manage.

Pherosphaera fitzgeraldii; photo from https://savingourspecies.environment.nsw.gov.au/managementsite/3752

Phytophthora pluvivora was first detected in Australia on an English oak, Quercus robur. However, it has since been recorded on native species in the Blue Mountains, including the critically endangered dwarf mountain pine (Pherosphaera fitzgeraldii) in a National Park.

SOURCES

Carnegie. A.J., B.A. Summerell, C. Trollip, F. Tovar, D.I. Smith, and J. McDonald. 2026. Sentinel trees for early detection of non-native forest pests and pathogens in Australia. Front. For. Glob. Change 9:1801183. doi: 10.3389/ffgc.2026.1801183

Haack, R.A. and R.B. Blank. 2025.  Susceptibility of English Oak (Quercus robur) to the Twolined Chestnut Borer, Agrilus bilineatus (Coleoptera: Buprestidae): Observations from Michigan. The Great Lakes Entomologist. 57: 113-125. https://doi.org/10.22543/0090-0222.2492

Hernández‐Gutiérrez, E., R.A. Nichols, and L.J. Kelly. 2026. Combined phylogenetic and geographic data can predict plant–pest interactions with high accuracy. New Phytologist (2026) doi: 10.1111/nph.71306

Peyton, J.M., S. Rorke, D.C. Aldridge, O.L. Pescott, K. Dehnen- Schmutz, D.G. Noble,  J. Sewell, A.J.A. Stewart,  T. Adriaens,  B.C. Beckmann,  J. R. Britton, J. Brodie1, P.M.J. Brown, I.C.N. Cavadino, P.F. Clark, A.M. Dunn, J.Foster, C. Harrower, M.C. Harvey, M.C. Jackson, T. Jones, C.A. Maggs, G. Martin, F. Mathews, A.C. Mill, D. Murphy,  E. Paganini, R. Payne, W. Rabitsch, T. Renals,    K. Schönrogge, R.H. Shaw, G.C. Smith, P.D. Stebbing, P.A. Stroh, H. Tidbury, E. Tricarico, J. Vallet,   K.J. Walker, L.E. Wood, C.A. Wood, B. Woodcock, H.E. Roy. 2026. Assessing the success of a horizon scanning approach in predicting invasive non- native species arrival. J Appl Ecol. 2026;63: https://doi.org/10.1111/1365-2664.70217

Posted by Faith Campbell

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

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

Or

https://fadingforests.org

U.S. Imports from Asia rise … & as more regions expand ports, the pest risk spreads to new places

Pananax ship; photo by 2005emsaguinden via Wikimedia

Imports from Asia, specifically China, had surged in the first half of 2025 as importers tried to get ahead of new tariffs. Blog They then fell sharply, although there was also a shift in Asian suppliers from China to Vietnam and India. At the end of 2025, experts expected the slump to persist into 2026. However, now we learn that U.S. imports from Asia jumped 13% from April to May, to 1.68 million TEUs (Michael Angell, Journal of Commerce, June 16, 2026). According to Politico, the shift to importing goods from Vietnam, and to a lesser extent to Thailand and Indonesia, has continued.

American cities continue to compete for to build larger ports so they can receive more cargo. Of course, more cargo means more incoming containers. As my blogs document (click “wood packaging” in the “Categories” section below the “Archives”), containers and especially the crates and pallets inside them too often transport wood-boring insects and other invasive species.

My source of information on these developments is from the Journal of Commerce website. Unfortunately, access is blocked by a paywall.

Recent reports concern port cities dredging and widening their ports in hope of attracting increased import volumes.

Norfolk; photo by PghPhxNfK via Wikimedia

Norfolk, Virginia

This month the Virginia Port Authority (VPA), Governor Abigail Spanberger and other federal, state, and local officials inaugurated the Port of Norfolk’s expanded capacity. At 55 feet, Norfolk is now the deepest and widest port along the East Coast. The project, begun in 2019, will allow Norfolk to handle vessels carrying up to 18,000 TEUs [twenty-foot equivalent containers]. Authorities are encouraging ocean carriers to call there.

The port was visited by 1,497 container ships over the past 12 months; nearly a quarter had a capacity greater than 11,000 TEUs.

Virginia’s container volumes grew on average 3% annually between 2017 and 2024. In 2025, total container volume fell 8% from 2024 because shippers hoped to avoid tariff deadlines by unloading cargo at a first or second port of call. Virginia was the six-busiest US port for imports this year through May, handling 635,205 TEUs. That was up 2.6% from the same five-month period a year ago. To attract shippers to Norfolk as a first or even second port of call for more container services, Virginia Port Authority CEO Sarah McCoy said, Virginia needs to emphasize rail links. This involves expanding the region’s distribution center network.

The project to dredge and widen the port began in 2019. The total project has a budget of $1.4 billion. The project included adding two ultra-large container vessel (ULCV) berths at each of its two container terminals. The final component is to renovate the North Berth, including developing a fifth ULCV berth, plus four new ship-to-shore cranes and semi-automated stacking cranes in its container yard. Completion is scheduled for mid-2027. At that time, the port’s total handling will reach 5.8 million TEUs. The International Longshoremen’s Association (ILA) is contesting installation of semi-automated stacking cranes in a series of lawsuits.

Other East Coast ports are also adding terminal capacity. This includes the Port of Baltimore, where a shipping company is developing a container terminal that includes handling two ULCVs simultaneously. Apparently they are not deterred by the months-long closure of the Port of Baltimore caused by a ship colliding with a bridge downstream from the port.  

[Information from Michael Angell, Senior Editor, East Coast Ports. “Norfolk aims to be preferred USEC gateway with deeper port” June 18, 2026]

U.S. Army Corps of Engineers dredge in the Savannah River

The Port of Savannah remains dominant. In 2025 Savannah and the roll on-roll of facility in Brunswick together handled nearly 5.7 million TEUs, an increase of 2.6% or 146,000 TEUs compared to 2024. Even so, Georgia Ports is financing a $4.5 billion port and inland infrastructure plan which will add five new container berths in Savannah, the most new berths of any U.S. port and one new RoRo berth in Brunswick. Port officials brag about their rapid turnover of cargo from ship to rail. Forty-two double-stack trains per week take this cargo to Atlanta, Memphis, Nashville, Charlotte and Orlando. The Port Authority also operates two inland terminals – in in Chatsworth and Gainesville, Ga.

Corpus Christi

As I have reported in previous blogs, Gulf Coast ports are also upgrading to receive more shipments. DP World, a Dubai-based terminal operator, is negotiating to develop a container terminal at the Port of Corpus Christi. This would open this port to container logistics.

Corpus Christi is already the third-busiest port in the US by gross tonnage, behind Houston and South Louisiana. The bulk of cargo is petroleum and bulk commodities. (In past years, dunnage associated with bulk commodities proved to cause pest-infestation problems in nearby Houston.)

dunnage piled on the dock at Houston; photo by S. Useman

Last year Corpus Christi completed an eight-year, $625 million project to widen and deepen its main shipping channel (from 47 feet to 54 feet). The expansion allows visits by super-post-Panamax container vessels.

[Information from Michael Angell, Senior Editor, East Coast Ports. “DP World begins talks with Corpus Christi for container terminal project” June 16, 2026]

Warehouse Capacity

Leaders of logistics managers note that importers and domestic manufacturers are diversifying their supply chains – both warehouse facilities and shipping routes – because of ongoing supply chain disruptions even years after COVID 19. While many industrial warehouses across the U.S. still have vacancies (averaging above 7%), some markets are filling up. They mention Chicago, Indianapolis, Memphis, Dallas, and Kansas City. These cities’ warehouse vacancies average ~5%. Indianapolis leads; asking rents for industrial space there have climbed more than 50% over the past five years. Phoenix also anticipates increased demand for space, although its current vacancy rate is 10.6% – the highest vacancy rate of the 25 largest markets.

The move away from Los Angeles-Long Beach began years ago. To move freight inland, shippers need options, particularly access to intermodal rail.

shipping containers at Long Beach in the early 2000s; photo courtesy of Bob Kanter of the Port of Long Beach

The experts attribute this growth to the need for more flexibile supply chains and demand for materials used in constructing data centers. Demand for the second category is reportedly strongest in the Southeast, followed by interior central markets.

[Information from William B. Cassidy, Senior Editor, Trucking. “US warehousing expanding faster at key inland hubs” June 18, 2026]

Posted by Faith Campbell

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

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

Or

https://fadingforests.org

Funding for USFS & APHIS – first Congressional actions

ash trees (Fraxinus spp.) killed by EAB along Mattawoman Creek, Prince Georges County, Maryland; photo by Leslie A. Brice

I report here on action so far on funding vital agencies in Fiscal Year 2047 (which begins on October 1, 2026). I describe the various programs roles in addressing the invasive species threat briefly in my earlier blog.

USDA Forest Service

The House Appropriations Committee approved the FY27 Interior Appropriations bill (which includes the USFS) in early June. I greatly appreciate Congress’ continued support for two USFS programs that are vitally important in protecting resilience of the Nation’s forests in the face of invasions by non-native pests and plants: Research and Development and Forest Health Management (in the State, Private, and Tribal lands division). The Trump Administration had – for the second year in a row – called for ending these programs’ specific appropriations.  

Research and Development

In my testimony I had asked the Subcommittee to maintain funding for R&D at the Fiscal Year 2026 Continuing Resolution level of $308 million. Instead the Subcommittee ignored the Administration’s request and provided $295 million – a fairly small reduction under the circumstances. Funding for the Forest Inventory and Analysis (FIA) program continues to see small increases — to $34 million.

While there is no specific line item for invasive species in the R&D budget, the report does encourage the USFS to address high priority invasive species, pests, and diseases, including the emerald ash borer, an unspecified “bark beetle”, spotted lanternfly, and Spruce Budworm. The list also includes three invasive plant species: buckthorn, Amur honeysuckle, and Callery pear. This language is not tied to a specific program, so it is unclear what will actually result.

In the R&D section of the report, the Committee “recognizes the significant damage invasive species can cause throughout forests, including urban forests, and encourages the USFS to continue reforestation efforts, including through the management of woody invasive species & tree planting in urban areas.” Again, the wording seems somewhat misplaced since the R&D program does not carry out tree planting.

State, Private, and Tribal forests

I had asked the Interior Appropriations Subcommittee to maintain funding for State, Private, and Tribal forests program at the FY26 Continuing Resolution level of $310.6 million. Again, appropriators ignored the Administration’s request and provided $283,500,000 – a fairly small reduction. The Forest Health Management program was funded at $58 – of which $16 million is specified for efforts on federal lands, $42 million for helping state and tribal agencies and private landowners to manage pests on their lands.

The Subcommittee report emphasized the importance of working with Colorado to curtail spread of mountain pine beetle d associated wildfire risk. Music to my ears is the Committee’s statement encouraging the USFS to work with state & local agencies to counter the high rate of tree mortality due to the goldspotted oak borer infestation in Southern California. It advised prioritizing insect research, prevention, suppression, & mitigation projects that support community wildfire protection & State forest action plans. Since none of the members of the House Interior Appropriations Subcommittee is from California, I am pleasantly puzzled.

coast live oak (Quercus agrifolia) killed by goldspotted oak borer; Heisey County Park, San Diego County, California. Photo by F.T. Campbell

The Interior Appropriations Subcommittee expressed continued concern about poor regeneration of eastern white oak (Quercus alba). (Of course, several other tree species are also regenerating poorly but a strong lobby is tied to oaks due to their economic importance.

i’iwi – a formerly common Hawaiian honeycreeper badly suppressed by avian malaria; photo by by James Petruzzi

Hawaii’s endangered birds

I am very pleased that the House Interior Appropriations Committee has provided $1,250,000 is for continuing research to protect Hawaiian forest birds from the dire extinction threat arising from non-native mosquitoes carrying avian malaria & other pathogens.

USDA Animal and Plant Health Inspection Service

APHIS is responsible for preventing the introduction and spread of pests and invasive plants that harm agriculture, including forests. APHIS policy guides port inspections carried out by the DHS CBP. APHIS inspects imported live plants. Unlike the USFS, APHIS has the support of the Trump Administration, so funding levels have remained steady. Of course, continuing introductions of new pests and spread of established ones – and inflation – have increased the cost of countering invasions, so the agency continues to fall behind despite its relatively privileged position.

The House of Representatives adopted the FY27 Agriculture Appropriations Bill in early June. I apologize for the obscurity of the FY26 funding levels. Figures are in millions of dollars.

FY2025 enacted                        FY27

APHIS total                                $1,148                                      $1,157

Plant health subtotal               $387.5                                      $387.6             

Agric. quarantine                      $35.5                                        $35.5

Field crop and rangeland           $12                                           $10

Pest detection                           $29                                           $29

Methods development               $21.5                                        $21

Specialty crops                          $206.5                                      $209

Tree and wood pests                  $59                                           $58.6

In its report, the Subcommittee on Agriculture Appropriations did not express concern about the issues that I had raised in my testimony. Instead, it mentioned several agricultural pests, e.g., citrus greening, fruit flies, a non-native beetle threatening nut orchards, and spotted lanternfly (Lycorma delicatula). The Subcommittee also urged APHIS to work with the USDA Forest Service to counter the spread of two native wood-borers, mountain pine beetle (Dendroctonus ponderosae) in Colorado and southern pine beetle (Dendroctonus frontalis). Since both are native, APHIS’ role is unclear. The Subcommittee mentioned two invasive plants: glossy buckthorn (Frangula alnus) – saying it threatens biodiversity, especially in the Allegheny National Forest in Pennsylvania; and Carizzo cane (Arundo donax), saying it contributes to tick invasions in addition to hampering detection of human immigrants along the Rio Grande.

sounder graphic by Jack Mayer, Savannah River National Laboratory

The bill increases funding for the national feral swine management program by $500,000. (I cannot determine total the appropriation). The Agriculture Appropriations Subcommittee had urged APHIS Wildlife Services to prioritize states with the largest invasive populations – although this choice contradicts standard advice for managing invasive species, including feral swine.

In one action linked to our concerns about wood-borer introductions via wood packaging, the Subcommittee encouraged APHIS to recognize sulfuryl fluoride as a treatment for logs, wood products, & wood packaging. This fumigant has been accepted under the international (ISPM#15) since 2013.

wooden pallets discarded next to wooded border in Glacier National Park, Montana; photo by F.T. Campbell

Posted by Faith Campbell

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

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

Or

https://fadingforests.org

Bioinvader Threat to Caribbean cacti – Who is Protecting Them?

Photo of infested cactus at Cabo Rojo National Wildlife Refuge, Puerto Rico. Taken August 20, 2018 by Yorelyz Rodríguez-Reyes

For 15 years I have maintained a profile of the Harrisia cactus mealybug Hypogeococcus pungens because it threatens columnar cacti in the subfamily Cactoideae from the Caribbean basin and possibly in the American Southwest and Mexico. My recent attempts to clarify the current situation have been frustrated by the apparent collapse of funding support for scientists trying to conserve these cactus species.

The dry regions of the Caribbean Islands are home to about 100 native cacti, 75% of which are endemic. According to the Center for Plant Conservation, 20 species are listed as threatened by the IUCN. Puerto Rico specifically is home to 14 cactus species, at least three of which are endemic.

How and when the mealybug first invaded the Caribbean and North America is unknown. The presence of the insect now known as H. pungens Hyp-C on Puerto Rico was detected in the Guánica Commonwealth Forest and Biosphere Reserve on the island’s southern coast in 2005 (Zimmerman et al. 2010). However, the actual introduction probably occurred about ten years earlier, in about 1996 (Poveda-Martinez et al. 2022).  See map of locations below.

In the 20 years since then, the mealybug has spread across the island’s dry districts. By 2010, it was estimated to be present on about 1,400 km2. By 2014 – nine years after detection — the mealybug had reached the small island of Caja de Muertos. The most recent survey of which I am aware (date unclear) detected the mealybug on 268 out of 445 cactus plants examined (60%) in 12 out of 39 sites examined (Poveda-Martinez et al. 2022). The mealybug is also killing native cacti on the nearby U.S. Virgin Islands (Poland et al. 2019), although I have found no data on this invasion or its impact.

Below – columnar cacti on St. John, US Virgin Islands; photos by F.T. Campbell

H. pungens Hyp‑C threatens seven of 14 native cactus species in Puerto Rico. Three of the cacti are endemic; two are federally listed as endangered species: Harrisia portoricensis and Leptocereus grantianus (USDA ARS). Since the mealybug’s detection in Puerto Rico, it has caused extensive damage to Pilosocereus royenii (Royen’s tree cactus), Leptocereus qaudricostatus (pitaya), Melocactus intortus (turk’s cap), and an introduced cultivar, Cereus hexagonus. It has caused minor damage to Stenocereus fimbriatus (Zimmerman et al. 2010). These cacti provide food or shelter for endemic bats, birds, moths and other pollinators (Segarra and Ramirez; USDA ARS).

The insect’s attack promotes abnormal gall-like growth on the stem and deformed flowers. These deformations severely affect infested plants’ reproduction and eventually survival (Poveda-Martinez et al. 2022).

Biological Control

When the mealybug was first detected Commonwealth and federal agencies tried to counter it. A search for possible biocontrol agents in the insect’s native range in Argentina began the 2010. While no funds have ever been appropriated for this activity, for several years the U.S. Department of Agriculture supported the work by allocating funds to the Agriculture Research Service Insect Behavior and Biocontrol laboratory in Gainesville, Florida, from broader programs. Dr. Stephen Hight took the lead, working with colleagues in South America. According to Dr. Hilda Diaz-Soltero, then a USDA official, these funds came primarily from the USDA Invasive Species Coordination Program and APHIS Eastern Region. In fiscal years 2017 and 2019, an additional ~$550,000 came in the form of grants under APHIS’ Plant Pest and Disease Management and Disaster Prevention Program. Link Scientists at the Center for Excellence in Quarantine and Invasive Species at the University of Puerto Rico devoted at least a decade to the search.

Scientists focused on two parasitoid wasps, Anagyrus cachamai and A. lapachosus (Hymenoptera: Encyrtidae). A third candidate, the predator Hyperaspis conclusa, was also assessed (Aguire et al.).

Research on the mealybug-wasps interaction uncovered troubling patterns. First, it has long been known that some mealybugs believed to be belong to the species Hypogeococcus pungens feed on columnar cacti while others feed on plants in two unrelated families, Amaranthaceae and Portulacaceae (USDA ARS; Zimmerman et al. 2010). Would the introduced wasps attack the cactus-feeding mealybug in sufficient numbers?

The confusion over how many mealybug species have been introduced – and where – severely hampered development of a program. (The mealybug has been introduced to control invasive cactus in Australia and South Africa. Most sources say it has been highly effective – prompting the initial concern when it appeared on Puerto Rico.) I have been unable to find any information about the status of the candidate biocontrol agents more recent than 2022.

Genetic Conservation

The USDA also partnered with the Naples (Florida) Botanical Garden to collect fruits and vegetative material for ex situ conservation. Rigorous phytosanitary procedures were followed to ensure the absence of the mealybug. Collections of fruits and vegetative material provided 1,298 cacti samples from 13 species, representing 1,173 maternal lines from 91 sites throughout Puerto Rico. A total of 90,720 seeds representing 8 species are banked at the NBG for long-term storage. Propagation of the vegetative material has 56% success, and plants are incorporated into the NBG’s living collections. (These figures include Opuntia cacti that are hosts of a second invasive insect, Cactoblastis cactorum.)  

Genetic Concerns

Scientists now consider Hypogeococcus pungens (Hemiptera: Pseudococcidae) to be a species complex composed of at least five putative species. The species are separated in part by the plants they use as hosts. Two of the complex have apparently been introduced to Puerto Rico: H. pungens Hyp‑C feeds on cacti; H. pungens Hyp‑AP feeds on hosts in the Portulacaceae & Amaranthaceae. Both evolved from putative source populations in Brazil (Poveda-Martinez et al. 2022).

The two species H. pungens Hyp-C and Hyp-AP are currently separated on Puerto Rico by host preferences and climatic niches. They also occupy different geographic areas. Scientists fear that ongoing climate change could allow H. pungens Hyp-C to establish farther into the island’s interior and in a large area in the north. Such range expansion would end the geographic separation. Overlapping of the two species is likely to exacerbate the threat to Puerto Rico’s cacti. Most directly, it would complicate implementation of management strategies, especially biological control. Intermixing of the two species could also facilitate hybridization which might result in more vigorous attacks or a broadened host range. Hybridization is frequent in closely related species (Poveda-Martinez et al. 2022).

The Mealybug is Frequently Introduced

Mealybugs that feed on cacti and believed to be in the species Hypogeococcus pungens made multiple appearances in southern California between 2000 and 2018 – in gardens and in nurseries. Confusingly, CDFA reports interception of the mealybug on alternanthera and ludwigia plants shipped from Florida (CDFA 2018). I have no more recent data. The population in Florida was reported to be present in 16 counties in 2009); it might be the species that feeds on plants other than cacti (Poveda-Martinez et al. 2022). Other populations has been reported in the Dominican Republic (no date) (CDFA 2018); and in Hawai`i in 2005 (Hawaii Department of Agriculture new pest report). A mealybug that feeds on Amaranthaceae and Portulacaceae was detected in 2000 in San Juan, Puerto Rico (Poveda-Martinez et al. 2022).

In the absence of control measures, scientists expect H. pungens Hyp-C to continue decimating Puerto Rican cactus diversity and threaten other cactus rich ecosystems across the Caribbean islands, Central America and, potentially, North America (Poveda-Martinez et al. 2022).

saguaro and organ pipe cacti in Organ Pipe Cactus National Monument; photo by F.T. Campbell

North America has more than 500 columnar cactus species in the Cactoideae (Zimmerman et al. 2010). Some of these cacti are already endangered, e.g., several Pediocactus. Others are totems of the desert, e.g., the saguaro (Carnegiea gigantea) and organ pipe (Stenocereus thurberi) cacti. Picture The larger ones, particularly, play important ecological roles. It is not known how vulnerable individual species are to the mealybug (Golubov pers. comm. January 2011). In Mexico several mealybugs in the same genus are already present. The natural enemies of these mealybugs might be able to attack H. pungens Hyp-C if it invades the country (Zimmerman et al. 2010). Despite the well-founded concern, apparently no funds have been allocated by governments or conservation organizations to studying the vulnerability of these cacti to one or more mealybugs in the Hypogeococcus genus.

The most likely pathway by which the mealybug is spread is the trade in plants for planting (the horticultural trade) (Zimmerman et al. 2010). A decade ago APHIS reported intercepting mealybugs on cactus (primarily on roots) imported from Germany, Peru, and Puerto Rico. APHIS has also intercepted several other mealybugs in the same genus – on plants (including orchids and bromeliads as well as cacti) from Belize, Costa Rica, Ecuador, Guatemala, Honduras, Mexico, Panama, Peru, and Venezuela (USDA APHIS alert).

A decade ago NatureServe and IUCN found that 31% of Earth’s cactus species were threatened with extinction. They named overharvesting (often for the illegal horticultural trade) and destruction of habitat by smallholder livestock ranching and farming. Did not mention predation by introduced insects – although that is now manifest not only in the cactus mealybug but also the cactus moth.

Sources

Aguirre, M. G. Logarzo, S. Triapitsyn, H. Diaz-Soltero, S. Hight, O. Bruzzone. 2023? Effect of egg production dynamics on the functional response of parasitoids

California Plant Pest and Disease Report. 2005. Vol. 22 No. 1. Covering Period from July 2002 through July 2005.California Department of Food and Agriculture. 2018.California Pest Rating for Hypogeococcus pungens Granara de Willink | Harrisia cactus mealybug Hemiptera: Pseudococcidae Pest Rating: A California Pest Rating for Hypogeococcus pungens Granara de Willink | Harrisia cactus mealybug Hemiptera: Pseudococcidae Pest Rating: A

Hawaii Department of Agriculture. 2006. https://hawaii.gov/hdoa/pi/ppc/2006-annual-report/new-pest-detections  (accessed 11/1/10)

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.

Poveda-Martinez, D. N.A. Salinas, M. Belen Aguirre, A.F. Sanchez-Restrepo, S. Hight, H. Diaz-Soltero, G. Logarzo,  and E. Hasson. 2022 Geonomic & ecol evidence shed light on the recent demographic history of two related invasive insects. Scientific Reports.

Segarra-Carmona, A.E., A. Ramirez-Lluch. No date. Hypogeococcus pungens (Hemiptera: Pseudococcidae): A new threat to biodiversity in fragile dry tropical forests.

Segarra-Carmona, A.E., A. Ramírez-Lluch, I. Cabrera-Asencio and A.N. Jiménez-López. 2010. First Report of a New Invasive Mealybug, the Harrisia Cactus mealybug Hypogeococcus pungens (Hemiptera: Pseudococcidae). J. Agrie. Univ. RR. 94(1-2):183-187 (2010)

Srivastava, M., P. Srivastava,  R. Karan, A. Jeyaprakash, L. Whilby, E. Rohrig, A.C. Howe,  S.D. Hight, and L. Varone. 2019. Molecular detection method developed to track the koinobiont larval parasitoid Apanteles opuntiarum (Hymenoptera: Braconidae) imported from Argentina to control Cactoblastis cactorum (Lepidoptera: Pyralidae). Florida Entomologist 102(2): 329-335.

Triapitsyn, Aguirre, Logarzo, Hight, Ciomperlik, Rugman-Jones, Rodriguez. 2018. Complex of primary and secondary parasitoids (Hymenoptera: Encyrtidae and Signiphoridae) of Hypogeococcus species. mealybugs (Hemiptera: Pseudococcidae) in the New World. Florida Entomologist Volume 101, No. 3 411

USDA Agriculture Research Service, Research Project: Biological Control of the Harrisia Cactus Mealybug, Hypogeococcus pungens (Hemiptera:pseudococcidae) in Puerto Rico Project Number: 0211-22000-006-10 Project Type: Reimbursable

Zimmermann, H.G., M.P.S. Cuen, M.C. Mandujano, and J. Golubov. 2010. The South American mealybug that threatens North American cacti. Cactus and Succulent Journal. 2010 Volume 82 Number 3

Countries Fall Short on Plant Conservation Efforts

Prostanthera cuneata – member of a genus endemic to Australia. Photo by Leonora (Ellie) Enking via Flickr

In 2023 a global meeting of plant conservation experts convened by The Royal Botanic Gardens, Kew (U.K.) released the 5th edition of a report on the State of the World’s Plants and Fungi.

Associate Professor of Plant Ecology and Conservation Science Rachael Gallagher from Western Sydney University had led the global evaluation of conservation assessments for unique flora species. She is also the lead author of an article (2023; full citation at the end of this blog) evaluating how well countries around the world met their treaty obligation to assess the conservation status of endemic plant species native to their territories. The analysis identified 221,399 endemic plant species in a total of 173 countries. The treasure is not distributed evenly. Five countries harbor a third of the endemic plant species: in descending order, Brazil, Australia, China, Mexico, and South Africa. (The United States, including its islands, ranks 8th.)

On average, countries completed assessments of just 34% of their endemic species. New Zealand and here and South Africa shone: they assessed 87% of their unique species. China assessed 71%. One of the world’s poorest countries, Madagascar, evaluated 42% of its ~10,000 endemic plant species. Reminder: tiny Madagascar ranks 6th in the number of endemic plants. Australia – one of the richest countries– carried out the process for 39% — slightly more than the global average. Other countries that are stewards of numerous endemic plants were below the average: Brazil reviewed 29%, Mexico assessed only 24%.

Rachael Gallagher and her colleagues in the Australian Biodiversity Council were quite critical of Australia’s low level of performance. They called on their countrymen to do much more to prevent the decline and extinction of the country’s unique plant species. Australia, as party to the Convention on the Conservation of Biological Diversity, has a treaty obligation to prevent extinction of species which occur nowhere else. Remember, Australia’s flora and fauna rank extremely high on a scale of phylogenetic distinctness as an heir of the isolated continent of Gondwanaland.

Gallagher and colleagues concede that many endemic plant taxa in Australia have huge ranges — averaging 235,829 km2. But these vast expanses do not prevent sudden population crashes caused by calamities. They mention the megafires of 2019–2020 and – over the longer term – climate change. I think of the invasion by the rust fungus Austropuccinia psidii.

When we think about Australia, we wonder at the kangaroos and koalas. I assume Australians consider their unusual fauna to be iconic symbols of their country. Why are they not equally committed to their flora – 88% of their plant species are endemic. Do they suffer from the same “plant blindness” I have encountered in the United States? South Africa undertook an assessment of her endemic flora that concluded that a quarter of these species are threatened. Sixty percent of the country’s 20,000 plant species are endemic.

a protea in South Africa’s fynbos; photo by Michael Wingfield

[I have found no parallel analysis of America’s endemic plant species. Our nation’s rank of 8th in number of endemic species is explained by the highly unique floras of the islands, especially the Hawaiian archipelago. More than 95% of native species on the Islands are endemic. This includes 67% of the large trees still present in the forests (Potter et al. 2023).]

This study reflects the findings of the International Union for the Conservation of nature (IUCN)’s 2024 Red List of Threatened Species. A decade-long global project had found that at least 16,425 of the 47,282 tree species (38%) assessed are at risk of extinction. Trees accounted for over one quarter of species on the IUCN Red List. Tree species are at risk of extinction in 192 countries around the world.

Sources

Gallagher, R.V., S. P. Allen, R. Govaerts, M.C. Rivers, A.P. Allen, D.A. Keith, C. Merow, B. Maitner, N. Butt, T.D. Auld, B.J. Enquist, W.L. Eiserhardt, I.J. Wright, J.C.O. Mifsud, S. Espinosa-Ruiz, H. Possingham, V.M. Adams. 2023. Global shortfalls in threat assessments for endemic flora by country. Plants, People, Planet. DOI: 10.1002/ppp3.1036

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

Posted by Faith Campbell

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

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

Or

https://fadingforests.org