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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

2017 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 which is now much easier to control. The latest prospective biological control agent is the galling fly Lophodiplosis indentata which is currently undergoing host range testing in quarantine. Old World climbing fern, 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 742,712 brown lygodium moths (Neomusotima conspurcatalis) and 321,000 mites (Floracarus perrepae) were released at remote and key conservation areas throughout central and south Florida. Outbreaks of the moth were observed in multiple locations in the winter of 2016-2017. Populations of the mite were also observed at multiple locations including Arthur R. Marshall Loxahatchee National Wildlife Refuge, on an island where bald eagles were nesting. Integrated pest management programs are being developed to determine how to effectively combine biological control with herbicide applications and prescribed burns to manage lygodium. New biological control agents for lygodium (L.) 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 are underway for L. stria on L. 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, in order to quantify its ability to sustain a population on a Caribbean species, L. volubile. ARS scientists from IPRL 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. Several individuals of the noctuid moth Callopistria sp. were also received from Hong Kong. A colony was established and host-range testing has been conducted with 20 non-target plant species. 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. Quarantine testing was completed of the first biological control agent of Chinese tallow, the flea beetle (Bikasha collaris). These results showed that the flea beetle was safe to release as it could only complete its life cycle on the target weed. Research is nearly complete on the second biological control agent, a moth Gadirtha fusca which shows this species is also highly specific to Chinese tallow. Ongoing surveys in China discovered a new potential agent, Sauris nr purpurotincta (Lepidoptera: Geometridae) but testing showed this species had a broad host range and was not suitable for field release. Other potential agents that might be useful include a new species of galling midge, possibly in the Lasioptera genus, which was introduced into quarantine. Currently, IPRL scientists are attempting to establish a colony of this midge to begin testing for safety and suitability. 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 including 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, and Thailand. Several insects found during these surveys were imported into Fort Lauderdale quarantine for further testing. These included species of an unknown tip binding moth, Strepsicrates sp., a stem boring moth Casmara sp., a fruit-feeding moth Mesophelps pos. albilinella, and a defoliating beetle Cryptocephalus sp. Host range testing on Strepsicrates and Cryptocephalus ruled these two species out based on their broad host range. Testing continues for Mesophleps and Casmara, though both show initial indications of broad host specificity. Brazilian peppertree, Schinus terebinthifolia, is one of the worst invasive species of southern Florida, occupying more area than melaleuca and lygodium combined. Host testing of the thrips Pseudophilothrips ichini, an agent developed for biological control of Brazilian peppertree, was completed and petitioned for release. The technical advisory committee (TAG) review was completed and passed a recommendation to USDA/APHIS for its release. Additional Brazilian collections yielded a defoliating caterpillar species from a complex of Paectes spp. The adults that emerged from these collections have been prepared and are undergoing morphological and DNA molecular determinations. These new species from these collections will be examined for suitable as biological control agents of Brazilian peppertree. Waterhyacinth, Eichhornia 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 considered established in southern and northern Florida locations. A total of 608,733 M. scutellaris were released in 6 counties in Florida during FY 2017. 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) has been 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 plant hopper has been tested in Ft. Lauderdale quarantine against 65 non-target plants and has shown a high degree of fidelity to waterlettuce. In addition, plants were severely damaged following exposure to this potential agent for 60 days. 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 that feeds only on air potato leaves and vine-tips. IPRL distributed 52,211 Lilioceris beetles to 195 locations in 8 counties of southern Florida during Fiscal Year 2017. In addition, ARS scientists from IPRL developed 5 field research sites in Florida that documented extensive feeding damage to the vines and growing tips which severely limited seasonal growth and caused unseasonal vine mortality, resulting in up to 95% reduction in bulbil production. Host specificity testing in quarantine of another agent, Lilioceris egena, is now completed with results that showed close fidelity of this beetle to its host. A petition to the Technician Advisory Group for the Biological Control of Weeds is being written. Earleaf acacia (Acacia auriculiformis) is a fast-growing, evergreen tree that invades agricultural and natural areas of Florida. A study was conducted to determine the feasibility for biological control of earleaf acacia. This study discovered new potential agents in the plant’s native range of Australia and compiled a test plant list following phylogenetic characterization of related taxa. Among the Australian discoveries were seed feeding weevils (Melanterius spp). Additionally, both larvae and adult defoliating chrysomelid beetles (Calomela sp . and pos . Dicranosterna sp.) were discovered along with seed feeding Bruchidae, foliage feeding Eriophyidae mites, leaf tying larvae (Lepidoptera: Gracillariidae), and two species of mirid bugs, including Riptortus sp.

1. New biological control agent for brazilian pepper. ARS researchers in Ft. Lauderdale, Florida, completed host range testing of the thrips, Pseudophilothrips ichini, and found this insect to be safe for release. A petition for general release was recommended by the USDA/APHIS Technical Advisory Group (TAG) for the Biological Control of Weeds. When the release is approved this biological control agent may provide land managers and farmers with a cost effective means of controlling Brazilian pepper by reducing the current reliance on herbicidal control.

2. New biological control agent for chinese tallow. ARS researchers in Ft. Lauderdale, Florida, completed host range testing of the flea beetle, Bikasha collaris and found this insect to be safe for release. A petition for general release was recommended by the USDA/APHIS Technical Advisory Group (TAG) for the Biological Control of Weeds. When the release is 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. Long-term decline of melaleuca seed production. ARS researchers in Ft. Lauderdale, Florida, monitoring long-term field research data on melaleuca found a 50% decline in seed rain over a 14-year period. In addition, melaleuca litterfall gradually decreased and non-melaleuca leaf fraction increased, indicating the return of a more diverse native plant community following the implementation of biological control.

4. Biocontrol of air potato restores native communities. ARS researchers in Ft. Lauderdale, Florida concluded a 5-yr long air potato biocontrol impact research project at five field research sites from four counties in Florida. Their research demonstrated that the air potato biological control program is responsible for a significant recovery in native plant communities through increases in plant species richness. These returning plant species were mainly natives that were suppressed, killed, or displaced by air potato vine blankets in numerous public and private natural areas throughout Florida.

Review Publications
Fung, J., Dyer, K.G., Wheeler, G.S. 2016. Life history and host range of Sauris nr. purpurotincta, an unsuitable biological control agent for Chinese tallowtree. Biocontrol Science and Technology. 27(1):17-27.
Wheeler, G.S., Dyer, K.G., Hight, S.D., Wright, S.A. 2017. Seasonal abundance of the adventive Chinese tallowtree herbivore Caloptilia triadicae and its parasitoids. Florida Entomologist. 100(1):52-56.
Wheeler, G.S., Duncan, J.G., Wright, S.A. 2017. Predicting spillover risk to non-target plants pre-release: Bikasha collaris a potential biological control agent of Chinese tallowtree (Triadica sebifera). Biological Control. 180:16-21.
Wheeler, G.S., Madeira, P.T. 2017. Phylogeny within the Anacardiaceae predicts host range of potential biological control agents of Brazilian peppertree. Biological Control. 108:22-29.
Zhang, B., Deangelis, D., Rayamajhi, M.B., Botkin, D. 2017. Modeling the long-term effects of introduced herbivores on the spread of an invasive tree. Landscape Ecology. 32(6):1147–1161.
Minteer, C., Tipping, P.W., Knowles, B.K., Valmonte, R., Foley, J.R., Gettys, L.A. 2016. Utilization of an introduced weed biological control agent by a native parasitoid. Florida Entomologist. 99:576-577.
Wheeler, G.S., Steininger, M.S., Wright, S.A. 2017. Quarantine host range of Bikasha collaris; a potential biological control agent of Chinese tallowtree (Triadica sebifera) in North America. Entomologia Experimentalis et Applicata. 163:184–196.
Manrique, V., Lake, E.C., Smith, M., Diaz, R., Franko, C., Pratt, P.D., Rayamajhi, M.B., Overholt, W.A. 2017. Comparative Evaluation of Development and Reproductive Capacity of Two Biotypes of Lilioceris cheni (Coleoptera: Chrysomelidae), Biological Control Agents of Air Potato (Dioscorea Bulbifera) in Florida. Annals of the Entomological Society of America. 110(3):310-316.
Rayamajhi, M.B., Pratt, P.D., Tipping, P.W., Leidi, J.G., Dray Jr, F.A., Madeira, P.T., Center, T.D. 2017. Attributes of naturally fallen (rained) melaleuca quinquenervia seeds to two habitat types of South Florida wetlands. American Journal of Plant Sciences. 8:1659-1671.
Jones, E.E., Wheeler, G.S. 2017. Life history and host range of Prochoerodes onustaria, an unsuitable biological control agent of Brazilian peppertree. Biocontrol Science and Technology. 27(4):565–580.
Wheeler, G.S., Manrique, V., Overholt, W., McKay, F., Dyer, K.G. 2016. Quarantine host range testing of Pseudophilothrips ichini, a potential biological control agent of Brazilian peppertree (Schinus terebinthifolia) in North America and Hawaii. Entomologia Experimentalis et Applicata. 162(2):204-217.
Broggi, E.J., Dyer, K.G., Wheeler, G.S. 2016. Host range testing and life history of the defoliator Hymenomima memor: an unsuitable biological control agent for S. terebinthifolia in the U.S.A. Biocontrol Science and Technology. 26(11):1565-1573.
Tipping, P.W., Martin, M., Gettys, L. 2016. A gall forming biological control agent suppresses vegetative growth of an invasive tree. Biocontrol Science and Technology. 26(11):1586-1589.
Smith, M., Wright, S.A., Wheeler, G.S., Purcell, M., Mankinson, J. 2017. Non-selective feeding and oviposition behavior of Cryptocephalus trifasciata (Coleoptera: Cerambycidae: Cryptocephalinae), precludes its use as a biological control agent for downy rose myrtle (Rhodomyrtus tomentosa). Biocontrol Science and Technology. 27(3):445-448.
Russell, A., Johnson, S., Ximena, C., McKay, F., Moshman, L., Madeira, P.T., Blair, Z.J., Diaz, R. 2017. Surveys in Argentina and Uruguay reveal Cyrtobagous salviniae (Coleoptera: Curculionidae) populations adapted to survive temperate climates in southeastern USA. Biological Control. 107:41-49.
Lake, E.C., Tipping, P.W., Rayamajhi, M.B., Pratt, P.D., Dray Jr, F.A., Wheeler, G.S., Purcell, M.F., Center, T.D. 2017. The role of melaleuca control in Everglades restoration: accomplishments and future plans. In: Van Driesche, R.G, Reardon, R.C., editors. Supressing over-abundant invasive plants and insects in natural areas by use of their specialized natural enemies. Morgantown, WV: Forest Health Technology Enterprise Team. p. 53-58.