Location: Invasive Plant Research Laboratory2020 Annual Report
Our goal is the environmentally safe, sustainable suppression of exotic invasive species that threaten natural, agricultural, and urban ecosystems in the United States with an emphasis on weeds. Objective 1: Develop biological control programs for invasive weeds threatening the Everglades, and similar southeastern ecosystems, through the discovery, identification, efficacy testing, safety testing, release, and evaluation of new biological control agents. Sub-objective 1.1. Elucidate the ecology and population dynamics of targeted weeds and their potential insect and pathogen biological control agents, and investigate the impact of weed suppression on community and ecosystem structure and function. Sub objective 1.2. Conduct faunistic and floristic inventories to discover natural enemies that may serve as biological control agents for targeted weed species. Sub-objective 1.3. Conduct risk analysis to determine environmental safety of new and existing potential biological control agents for weeds. Objective 2: Improve current biological control programs of invasive weeds in the Everglades, and similar southeastern ecosystems, by developing integrated weed management strategies.
As described above, biological control research progresses in a stepwise fashion and our objectives detailed below are interconnected and flexible. The objectives are intentionally general to encompass the various weed targets and natural enemies that are currently under investigation, as well as those that may be added during the life of the research project. The first objective contains three sub-objectives that address the ecology of the weed, the discovery of potential agents, and the determination of their safety for release. The second objective focuses on the integration of biological control with other methods. A Milestone Table is prepared for each sub-objective and provides details on the tested hypotheses, scientific assignments, annual goals (milestones), and expected products of the research.
Melaleuca quinquenervia ('melaleuca') is an evergreen tree that was introduced into southern Florida in 1886 and by 1994 had infested about 800 square miles. Infestations of melaleuca outcompete native plants, eliminate animal habitats, increase fires, disrupt nutrient storage and cycling, and affect human health. Classical biological control programs at the USDA-ARS Invasive Plant Research Lab (IPRL) in Ft. Lauderdale, Florida, have transformed this plant into a less invasive form that no longer dominates the landscape and is now much easier to control using conventional methods. The latest prospective biological control agent is the galling fly Lophodiplosis indentata. A completed host range examination was submitted to the Technical Advisory Group (TAG) for evaluation, and in May 2020 the TAG recommended L. indentata for release. Old World climbing fern, Lygodium microphyllum, ('lygodium') is a climbing fern native to tropical Asia that has invaded Florida and is smothering tree islands, cypress domes, pine woodlands, and tropical hammocks in the Everglades. To date, IPRL has developed and established a moth and a mite whose ranges continue to increase across Florida. An additional 274,562 brown lygodium moths (Neomusotima conspurcatalis) and 1,107,701 mites (Floracarus perrepae) were released at remote and key conservation areas throughout central and south Florida. Outbreaks of the moth continue to be observed in multiple locations leading to browning out of lygodium populations. ARS scientists continue to learn more about the biology of F. perrepae to optimize rearing and release methods. The mite has established in many locations in Florida and can cause a four-fold reduction in rachis growth rates compared to undamaged rachises. A new study showed that both biological control agents colonized Lygodium regrowth in less than 1 year following prescribed burns. Furthermore, following herbicide treatments, the mite preferentially attacked young lygodium sporelings and regrowth. New research is underway to begin quantifying the damage of these agents to Lygodium in the field. New biological control agents for lygodium continue to be developed including two leaf feeding moths, a sawfly, and four species of stem borers. The moth, Lygomusotima stria, shows high specificity after quarantine testing against 69 non-target plants. Multigenerational tests have been completed for L. stria on the U.S. native plant L. palmatum and the invasive L. japonicum, whose range overlaps those of L. palmatum and L. microphyllum. Similar testing is underway for the lygodium sawfly, Neostrombocerus albicomus, to quantify its ability to sustain a population on a Caribbean species, Lygodium volubile. The noctuid moth Callopistria exotica has been tested against 44 non-target species with plant production and acquisition underway for additional species. This insect feeds voraciously and early results indicate that is a lygodium specialist. Chinese tallow, (Triadica sebifera), is an invasive tree that has invaded about 500,000 acres of southern U.S. forests where it reduces timber harvests and wildlife habitat. The TAG approved the release of the first biological control agent of Chinese tallow, the flea beetle (Bikasha collaris). A TAG petition for a second biological control agent, the moth Gadirtha fusca, was submitted after research showed this species to be highly specific to Chinese tallow. TAG and U.S. Fish and Wildlife Service (USFWS) have recommended both species for field release. Currently we are waiting for USDA/APHIS to post this action in the federal register and issue a release permit. Research to maximize agent production indicated that potting media did not affect rearing success of the root feeding flea beetle, B. collaris. Rearing conditions for G. fusca, including survival, development rate, pupal weights, and fecundity where greatest at 25 C temperature. Diapause in G. fusca larvae was induced by short photoperiod resulting in greater pupal weights and slower development rates. Rhodomyrtus tomentosa (downy rose myrtle) is a tall shrub that invades biologically important habitats like the Everglades in Florida and also forests, grasslands, and pastures in Hawaii. Biological control may offer a solution to this problem and surveys for potential agents have been conducted in mainland China, Hong Kong, Sri Lanka, Malaysia, Singapore, Indonesia, and Thailand. Several insects found during these surveys were imported into Fort Lauderdale quarantine for further testing. These included species of the stem boring moth Casmara subagronoma and a fruit-feeding moth Mesophelps albinella. Although testing is not yet completed, these species may prove to be unsuitable because the initial data suggests they are not specific enough to use safely against this weed. Efforts are underway to describe Casmara subagronoma and Mesophleps albinella. Brazilian peppertree, Schinus terebinthifolia, is one of the worst invasive species of southern Florida, occupying more area than melaleuca and lygodium combined but also in displacing and degrading Florida’s pristine ecosystem which includes the Florida Everglades Ecosystem. A release permit for a thrips biological control agent, Pseudophilothrips ichini, was issued in May 2019. This species is being mass produced at our facility for release throughout Florida and at field nursery plots. To date, 158,700 adults have been released at sites in Broward, Collier, Hendry, Miami Dade, and Okeechobee county and at biological control impact monitoring sites in Big Cypress National Preserve. Currently, the thrips are being widely released and preliminary results indicate that field populations have established at numerous locations. Effective sampling methods are being developed to monitor the thrips population and include a combination of color sticky traps that are baited with aggregation pheromones. Waterhyacinth, Pontederia crassipes, is considered the worst floating aquatic weed on earth, damaging ecosystems and entire economies of developing countries. The planthopper Megamelus scutellaris was the first new biological control agent released against waterhyacinth in more than 30 years and is now widely established in southern and northern Florida locations. A total of 176,410 M. scutellaris were released in 7 sites in Florida during FY 2020. The agents have dispersed up to 6.4 km from release sites, including through areas sprayed with herbicides and across terrestrial landscapes. Waterlettuce, Pistia stratiotes, is a serious floating weed in Florida and the southeastern U.S. A new species of planthopper (Lepidelphax pistae) was collected in Argentina, colonized in Ft. Lauderdale quarantine, and is currently being tested to determine its environmental safety as a biological control agent for waterlettuce, Pistia stratiotes, another serious floating aquatic weed. To date, the planthopper has been tested in Ft. Lauderdale quarantine against 42 non-target plants and has shown a high degree of fidelity to waterlettuce. Air potato (Dioscorea bulbifera) vine is one of the most invasive climbing vines of exotic origin. It has spread throughout public and private forested properties in all 67 Florida counties and in other adjacent states. IPRL has developed two genotypes (Nepalese and Chinese) of a biological control beetle Lilioceris cheni that feed only on air potato leaves and vine-tips. To date during FY2020, IPRL produced and released 655 adults. Mass rearing efforts for this species have been terminated and resources redirected towards the new Brazilian pepper biological control agent. Host specificity testing in quarantine of another agent, Lilioceris egena, was completed and a TAG petition was submitted and approved with minimal comments. US Fish & Wildlife has signed off on the proposed release of this insect, but the regulatory process has been delayed (awaiting listing in the Federal Register for public comments) due to the Covid-19 pandemic. Earleaf acacia (Acacia auriculiformis) is a fast-growing, evergreen tree that invades agricultural, disturbed and natural areas of Florida in the wetland/upland ecotone. Extensive field surveys in Australia discovered dozens of potential agents including various seed feeding beetles, leaf feeding beetles (Calomela sp. and Dicranosterna sp.), foliage feeding mites, fruit galling flies, leaf tying caterpillars, two species of mirid bugs, including Riptortus sp., and a galling wasp, Trichilogaster sp. Foreign surveys for additional agents have been scaled back and only include unsurveyed areas in the indigenously-controlled Arnhemlands in Northern Territory. The beetle Calomela intermerata passed initial screening for host specificity in Australia and has been imported into the quarantine facility in Fort Lauderdale where it is currently undergoing host range evaluation, biology studies, and impact assessments. Additionally, rearing protocols for Trichilogaster have been established and host range testing will commence shortly. A Next Generation GBS population study, displaying the origins of the Florida invasive population as the Northern Territories, Australia, will soon be published.
1. New mass rearing project initiated for biological control agent for Brazilian pepper. The thrips biocontrol agent Pseudophilothrips ichini was recently selected for inclusion into the Comprehensive Everglades Restoration Plan (CERP) mass rearing program by ARS scientists at Ft. Lauderdale, Florida. This biological control agent may provide land managers and farmers with a cost effective means of controlling Brazilian pepper by reducing the current and expensive reliance on herbicidal control.
2. New biological control agent for Chinese tallow. Host range testing indicated the moth Gadirtha fusca will be safe for release. This release was recommended by TAG and U.S. Fish and Wildlife Service ARS scientists at Ft. Lauderdale, Florida. We are waiting for the posting of this action in the federal register. When the release is ultimately approved, this biological control agent may provide land managers and farmers with a cost-effective means of controlling Chinese tallow by reducing the current reliance on herbicidal control.
3. New biological control agent for air potato. ARS scientists at the Invasive Plant Research Laboratory completed host range testing for a new biological control agent, the beetle Lilioceris egena, that eats the reproductive bulbils (‘potatoes’) associated with air potato. The proposed release permit is currently awaiting listing on the federal register for public comments as one of the final steps in the regulatory process.
4. New biological control agent for melaleuca. ARS scientists at Invasive Plant Research Laboratory completed host range testing for a new biological control agent, the pea-galling fly Lophodiplosis indentata, that forms extensive pea galls on melaleuca foliage. A TAG petition was submitted and approved. It is currently under further review by APHIS and a permit is expect in late FY21 or early FY22.
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