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ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Research Project #430076

Research Project: Identification, Evaluation, and Implementation of Biological Control Agents for Invasive Weeds of Southeastern Ecosystems

Location: Invasive Plant Research Laboratory

2019 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.

Progress Report
Melaleuca quinquenervia ('melaleuca') is a tall 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 which is now nearing completion of host range testing in quarantine. A petition for regulatory consideration is being prepared for submission to the technical advisory group (TAG) for the biological control of weeds. Old World climbing fern, Lygodium microphyllum, ('lygodium') (L. microphyllum) 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. This fast-growing fern produces enormous numbers of spores that can travel long distances on the slightest breeze and, as a result, this weed continues to expand its range in Florida. To date, IPRL has developed and established a moth and a mite whose ranges continue to increase across Florida. An additional 146,333 brown lygodium moths (Neomusotima conspurcatalis) and 920,048 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 Floracarus perrepae (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. Integrated pest management programs are being developed to effectively combine biological control with herbicide applications and prescribed burns to manage lygodium. Preliminary data suggest the mite preferentially attacks young lygodium sporelings and regrowth following herbicide treatments. 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 (L. stria), shows high specificity after quarantine testing against 69 non-target plants. Multigenerational tests are underway for L. stria on the U.S. native plant Lygodium palmatum and the invasive Lygodium 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. IPRL scientists received shipments of the newly described lygodium stem borer, Siamusotima disrupta from Hong Kong and are developing rearing methods for this poorly known species so that it can be tested. Additional individuals of the noctuid moth Callopistria exotica were also received from Hong Kong to support IPRL quarantine testing which have now examined 39 non-target 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 also recommended this species for field release in 2018. Currently both species are before U.S. Fish and Wildlife Service awaiting a letter of concurrence. Other potential agents that might be useful include a new species of galling midge, possibly in the Schizomyia genus, which was introduced into quarantine. Also, a leaf rolling caterpillar Dichomeris cymatodes was collected in China during the summer. This species was colonized in IPRL quarantine and is being tested for safety and suitability for field release. Additional herbivore pressure from biological control agents is needed to reduce the performance of this invasive weed. 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. Downy rose myrtle thrives in forest understories, preventing natural fire events, disrupting nutrient cycles while outcompeting native plants for light and nutrients. 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 sp. and a fruit-feeding moth Mesophelps albilinella. 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. Brazilian peppertree, Schinus terebinthifolia, is one of the worst invasive species of southern Florida, occupying more area than melaleuca and lygodium combined. A release permit for a thrips biological control agent, Pseudophilothrips ichini, was issued in May 2019. This species and a psyllid Calophya latiforceps will be mass produced at our facility for release throughout Florida. Research has been initiated to develop field nursery plots for establishment and mass production of the thrips and psyllid biological control agents. Several new species have been discovered while conducting field surveys in Brazil and Argentina including a new species of sawfly and five moth species. Two of the moth species were colonized in quarantine and tested for safety but were found to feed on non-target plants and thus will not be pursued further. Waterhyacinth, Ponderia crassipes, is considered the worst floating aquatic weed on earth, damaging ecosystems and entire economies of developing countries. The planthopper Megamelus scutellaris (M. 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 363,485 M. scutellaris were released in 13 sites in Florida during FY 2019. The agents have dispersed up to 6.4 km from release sites on Lake Okeechobee, including through areas sprayed with herbicides. 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. Quarantine based studies on its impact on waterlettuce have been completed and published. Studies on its development at different temperatures have also been completed and the data are being analyzed. 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 biotypes (Nepalese and Chinese) of a biological control beetle Lilioceris cheni (L. cheni) that feed only on air potato leaves and vine-tips. To date during FY 19, IPRL has distributed 27,905 L. cheni beetles to 130 locations in southern Florida. In addition, ARS scientists from IPRL have developed models for landscape level L. cheni biocontrol impact evaluation that can be used with minimal effort. Host specificity testing in quarantine of another agent, Lilioceris egena, was completed and a TAG petition was submitted and approved with minimal comments. Consideration for a release permit now moves to APHIS and U.S. Fish & Wildlife. Earleaf acacia (Acacia auriculiformis) is a fast-growing, evergreen tree that invades agricultural and natural areas of Florida. A feasibility study determined that a classical biological control had good potential for suppressing this species. Field surveys in Australia discovered several potential agents including various seed feeding beetles, leaf feeding beetles (Calomela sp. and Dicranosterna sp.), foliage feeding mites, fruit galling flies, leaf tying caterpillars, and two species of mirid bugs, including Riptortus sp. Foreign surveys for additional agents are ongoing. 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.

1. New biological control agent for Brazilian pepper. ARS scientists in Ft. Lauderdale, Florida, recently obtained authorization for field release of the thrips biocontrol agent Pseudophilothrips ichini. Thrips feeding under greenhouse conditions reduced Brazilian pepper seedling growth by 80%. 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. ARS scientists in Ft. Lauderdale, Florida, completed host range testing of the moth Gadirtha fusca and found this insect to be safe for release. A TAG petition for general release was approved and it is currently under review by APHIS. 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 in Ft. Lauderdale, Florida, completed host range testing for a new biological control agent, the beetle Lilioceris egena, that eats the reproductive bulbils (‘potatoes’) associated with air potato. A TAG petition was submitted and approved with minimal comments. It is currently under further review by APHIS.

4. No indirect effects of biological control. ARS scientists in Ft. Lauderdale, Florida, through a National Institute of Food and Agriculture funded research project examining the indirect effects of biological control found no evidence that the release and establishment of weed biological control agents negatively influences other native insects in both similar aquatic and terrestrial habitats.

Review Publications
Rayamajhi, M.B., Pratt, P.D., Tipping, P.W., Center, T.D., Leidi, J.G., Rodgers, L. 2018. Natural-enemies affect the seed and litter fall dynamics of Melaleuca quinquenervia in the wetlands, and influence long-term species diversity in leaf-litter. Wetlands Ecology and Management. 27(1):125-139.
Sebesta, N., Jones, I.M., Lake, E.C. 2018. First report of foliar nectar production by Lygodium microphyllum (Lygodiaceae), an invasive fern in Florida. American Fern Journal. 108(4):180-183.
Goode, A.B., Pasachnik, S. 2019. Flight response and human habituation in an insular endemic lizard. Herpetological Review. 49(2):215-217.
Chamely-Wiik, D., Haky, J., Louda, D., Romance, N., Goode, A.B., Vitale, M. 2018. The effects of a University/Secondary school partnership on the communication skills of STEM graduate students. International Journal of Science Education: Part B. 9(1):72-81.
Wheeler, G.S., Jones, E., Wright, S.A., Dyer, K.G. 2018. Quarantine host range and natural history of Gadirtha fusca, a potential biological control agent of Chinese tallowtree (Triadica sebifera) in North America. Entomologia Experimentalis et Applicata. 166:894-906.
Boeve, J., Rozenberg, R., Mc Kay, F., Wheeler, G.S. 2018. Toxic peptides in populations of two pergid sawflies, potential biocontrol agents of Brazilian peppertree. Journal of Chemical Ecology. 44(12):1139-1145.
Campbell, J., Grodsky, S., Halbritter, D.A., Vigueira, P., Vigueira, C., Keller, O., Greenberg, C. 2019. Asian needle ant (Brachyponera chinensis) and woodland ant responses to repeated applications of fuel reduction methods. Ecosphere. 10(1):1-12.
Rayamajhi, M.B., Rohrig, E., Leidi, J.G., Kerr, C., Salcedo, E., Poffenberger, R., Smith, M., Lake, E.C., Dray Jr, F.A., Pratt, P.D., Tipping, P.W., Center, T.D. 2019. Herbivory by the biocontrol agent Lilioceris cheni suppresses propagule production and smothering ability of the invasive vine Dioscorea bulbifera. Biological Control. 130:1-8.
Goode, A.B., Minteer, C., Tipping, P.W., Knowles, B.K., Valmonte, R., Foley, J., Gettys, L. 2019. Host range of Lepidelphax pistiae (Hemiptera: Delphacidae) and its potential impact on Pistia stratiotes L. (Araceae). Biocontrol Science and Technology. 29(7):706-714.
Hayden, J., Wheeler, G.S., Dyer, K.G. 2019. Amended identification of Oxydia (Lepidoptera: Geometridae) on Brazilian peppertree. Biocontrol Science and Technology. 29(4):400-404.
Jones, I., Lake, E.C. 2018. Interactions between two biological control agents on Lygodium microphyllum. Insects. 9(4):180.
Halbritter, D.A., Gordon, J., Keacher, K., Avery, M., Daniels, J. 2018. Evaluating an alleged mimic of the monarch butterfly: Neophasia (Lepidoptera: Pieridae) butterflies are palatable to avian predators. Insects. 9(4):150.
Tipping, P.W., Foley, J., Gettys, L., Minteer, C. 2018. Assessing the risk of Eccritotarsus eichhorniae to pickerelweed, Pontederia cordata in North America. Biocontrol Science and Technology. 28(4):332-340.
Wheeler, G.S., Jones, E.E., Broggi, E., Halbritter, D.A. 2018. The impact and production of the Brazilian peppertree biological control agent Pseudophilothrips ichini (Thysanoptera: Phlaeothripidae) is affected by the level of host-plant fertilization. Biological Control. 121:119-128.
Halbritter, D.A., Willett, D., Gordon, J., Stelinski, L., Daniels, J. 2018. Behavioral evidence for host transitions in plant, plant parasite, and insect interactions. Environmental Entomology. 47(3):646-653.
Wheeler, G.S., Dyer, K.G., Broggi, E., Ding, J., Purcell, M., Madeira, P.T. 2018. Molecular comparisons of native range collections of Gadirtha fusca, a potential biological control agent of Chinese tallowtree. Biocontrol Science and Technology. 28(8):796-804.
McCulloch, G., Hereward, J., Lake, E.C., Smith, M., Purcell, M., Walter, G. 2018. The complete chloroplast genome of the invasive fern Lygodium microphyllum (Cav.) R. Br. Mitochondrial DNA Part B. 3(2):746-747.
Goode, A.B., Minteer, C., Tipping, P.W., Knowles, B.K., Valmonte, R., Foley, J., Gettys, L. 2019. Small-scale dispersal of a biological control agent – Implications for more effective releases. Biological Control. 132:89-94.
Purcell, M., Harms, N., Grodowitz, M.J., Zhang, J., Ding, J., Wheeler, G.S., Zonneveld, R., Dechenon, R. 2019. Exploration for candidate biological control agents of the submerged aquatic weed Hydrilla verticillata, in Asia and Australia 1996–2013. Biocontrol. 64(3):233–247.
Halbritter, D.A., Wheeler, G.S. 2019. Organic mulch can increase the survival of a weed biological control agent during laboratory mass rearing. Biocontrol Science and Technology. 29(9):852-859.
Mc Kay, F., Dellape, G., Dyer, K.G., Wheeler, G.S. 2019. New record of Brontocoris tabidus (Hemiptera: Pentatomidae) attacking larvae of Heteroperreyia hubrichi (Hymenoptera: Pergidae). Journal of the Entomological Society of Argentina. 78(2):22-25.
McCulloch, G., Makinson, J., Zonneveld, R., Purcell, M., Brookes, D., Gurdasani, K., Lake, E.C., Raghu, S., Walter, G. 2019. Scrutinizing biological control survey data from the native range – the phylogeny and Lygodium fern host associations of Musotiminae moths. Biological Control. 134:123-129.
Lake, E.C., Kula, R.R., Gates, M.W., Smith, M., Minteer, C., Tipping, P.W. 2019. The first pupal parasitoids of Neomusotima conspurcatalis Warren (Lepidoptera: Crambidae), a biological control agent of Lygodium microphyllum (Cav.) R. Br. (Polypodiales: Lygodiaceae) in Florida. Proceedings of the Entomological Society of Washington. 121(2):314-319.
David, A.S., Quintana-Ascencio, P., Menges, E., Thapa-Magar, K., Michelle, A., Christopher, S. 2019. Soil microbiomes underlie population persistence of an endangered plant species. The American Naturalist. 194(4).
David, A.S., Jones, I., Lake, E.C. 2019. Windspeed predicts population dynamics of the eriophyid mite Floracarus perrepae on invasive Old World climbing fern (Lygodium microphyllum) in a shade house colony. Experimental and Applied Acarology. 78:263–272.