Location: Invasive Plant Research Laboratory
2024 Annual Report
Objectives
The objectives of this project plan are to develop environmentally safe, self-sustaining methods for the management of invasive weeds of exotic origin that threaten ecologically sensitive aquatic and terrestrial ecosystems of the United States, with a focus on the southeastern region. The following four objectives are relevant to the NP 304 Action Plan, Component 2 – Weeds; Problem Statement 2B: Biological control and ecosystem research and Problem Statement 2C: Integrated approaches to weed management.
Objective 1: Identify and prioritize invasive weeds that negatively affect ecologically sensitive terrestrial and aquatic ecosystems of the southeastern United States. [C2, PS 2C]
Objective 2: Survey native habitats of the candidate weeds in their geographical areas of origin for potential biological control agents. Acquire and characterize biological control agents and conduct thorough host-specificity tests informed by molecular phylogeny to determine fundamental host range. [C2, PS 2B]
Objective 3: Deploy APHIS-approved biological control agents and evaluate their efficacy by documenting impacts to target weed populations. [C2, PS 2B]
Objective 4: Evaluate impact of biological control projects on native plant diversity, invertebrate food webs, and plant disease dynamics at community and landscape levels. Develop integrated methods to improve overall weed management efforts. [C2 PS 2B and 2C]
Approach
Biological control research is a dynamic process and thus the proposed research objectives detailed below are often interconnected, flexible, with feedback loops. Although we have presented discrete research objectives in a generalized fashion to accommodate the various weed targets and their natural enemies which are currently under investigation, some may be removed and others added during the life of the proposed 5 yr research project. A Milestone Table has been prepared for each objective which details the hypotheses, scientific assignments, annual goals (milestones), and expected outcomes of the given research activities
Progress Report
Objective 1: ARS researchers at Fort Lauderdale, Florida held meetings with representatives from the Florida Fish & Wildlife Conservation Commission (FWCC), the South Florida Water Management District (SFWMD), and the U.S. Army Corps of Engineers (USACE) as well as members of the Florida Invasive Species Council (FISC) and Everglades Cooperative Invasive Species Management Area (eCISMA) discussing and prioritized potential weed targets. Fresh approaches to weeds like waterhyacinth and waterlettuce have consequently been initiated and new weeds like mosquito fern, Australian pine tree, and seaside vetch identified as possible targets.
Objective 2: Native range surveys for potential biological control agents of Cogongrass were conducted in Australia, Japan, Kenya, Portugal, South Africa, and South Korea. New discoveries include an unknown smut disease from Portugal; an unknown rust from Kenya; a gall former Lasioptera sp., a rhizome feeder (2 spp), and several stem boring weevils from Australia; and a stem boring caterpillar Acrapex azumai from Japan. Molecular studies are underway to refine our understanding of which waterways harbor native versus non-native genotypes, or both, of waterlettuce in Florida. Molecular studies are also underway to provide finer-grained detail on what foreign populations of Lygodium have contributed to invasive populations in Florida. Testing for three potential biological control agents of L. microphyllum has been completed. Petitions for release of all three species have been submitted to the regulating body, the Technical Advisory Group (TAG). Recommendations for release have been issued by TAG for two of these species, the defoliating moth Callopistria exotica and the sawfly Neostrombocerus albicomus. The petition for the third species, Lygomusotima stria, was submitted to TAG for review during May.
Objective 3: Mass rearing programs have resulted in releases this FY of over 20 million Floracarus perrepae mites and over 100,000 Neomusotima conspurcatalis moths targeting Old World climbing fern (Lygodium microphyllum), over 85,000 Lilioceris egena beetles targeting air potato vine (Dioscorea bulbifera), and nearly 400,000 Pseudophilothrips ichini thrips targeting Brazilian peppertree (Schinus terebenthifolia). The Lygodium insects are widely dispersed throughout southern Florida and produce occasional “brown-outs” where larval feeding causes fern leaves to die. This impact is ephemeral though. The air potato beetles attack bulbils (a sibling species attacks leaves); we’re studying how much damage is required to stop germination. Brazilian peppertree thrips have produced very heavy canopy damage and notable thinning at several sites this fiscal year. Canopy thrips damage scores jumped from 21.9% from 2023 to 35.9% thus far in 2024; this means that 35.9% of any canopy surveyed at a field site, on average, has some form of thrips damage present (crinkled leaves and/or dead tips). Staff are using a state-of-the-art vertical takeoff and landing, fixed-wing drone to collect multispectral images of 100 x 20 m plots of Brazilian peppertree regrowth following a clearcutting treatment, with a goal of comparing thrips-infested plots to thrips-free plots over the course several years.
Objective 4: Effects of inclement weather and covid-related supply chain issues combined to delay full deployment of booms on Lake Okeechobee until this year. These are now in place and fully operational. A trip to South Africa in August will produce genotypes of the waterhyacinth planthopper Megamelus scutellaris for mass rear and release on the lake beginning this fall.
Accomplishments
1. Callopistria exotica TAG petition submitted. Host testing was completed by ARS researchers at Fort Lauderdale, Florida on the moth Callopistria exotica, a proposed Lygodium bioagent. A petition was submitted to APHIS’ Technical Advisory Group on Biological Control of Weeds, which recommended to APHIS that this moth be approved for release. APHIS is now preparing an Environmental Assessment in furtherance of the regulatory process required prior to issuing a release permit.
2. Neostrombocerus albicomus TAG petition submitted. Host testing was completed by ARS researchers at Fort Lauderdale, Florida on the sawfly Neostrombocerus albicomus, a proposed Lygodium bioagent. A petition was submitted to APHIS’ Technical Advisory Group on Biological Control of Weeds, which recommended to APHIS that this moth be approved for release. APHIS is now preparing an Environmental Assessment in furtherance of the regulatory process required prior to issuing a release permit.
3. Lygomusotima stria TAG petition submitted. Host testing was completed by ARS researchers at Fort Lauderdale, Florida on the moth Lygomusotima stria, a proposed Lygodium bioagent. A petition was submitted to APHIS’ Technical Advisory Group on Biological Control of Weeds, who has not made a recommendation yet.
4. Cogongrass insects imported into Q. A crown boring moth (Emmalocera latilimbella) and a shoot boring fly (Atherigona sp.) were imported from Australia into the USDA Biocontainment lab in Fort Lauderdale for host range testing as possible biocontrols of cogongrass.
Review Publications
Mcavoy, T.J., Mays, R., Goldstein, S.L., Dray Jr, F.A., Yu, Z., Reardon, R., Salom, S.M. 2023. Additional host range testing of eucryptorrhynchus brandti (Coleoptera: Curculionidae) for the biological control of tree-of-heaven, ailanthus altissima (Simaroubaceae) in the U.S.A. Biocontrol Science and Technology. 1-26. https://doi.org/10.1080/09583157.2023.2294219.
Goode, A.B., Tipping, P.W., Dray Jr, F.A., Valmonte, R.J., Knowles, B.K., Pokorny, E.N. 2023. Effects of invasive plant haplotypes on a biological control agent (Lepidelphax pistiae) fecundity and impact. Biocontrol Science and Technology. https://doi.org/10.1080/09583157.2023.2272229.
Pemberton, R., Wheeler, G.S., Madeira, P.T. 2023. Bee (Hymenoptera: Apidae) pollination of Vanilla planifolia in Florida and their potential in commercial production. Florida Entomologist. 106(4):230-237. https://doi.org/10.1653/024.106.0404.
Manrigue, V., Kraus, E., Schaffer, C., Diaz, R., Kelm, C., Poffenberger, R., Murray, R., Smith, M., Dray Jr, F.A., Leidi, J.G., Lake, E., Rayamajhi, M., Minteer, C., Mass, J.L., Hight, S.D. 2023. Assessing the status of biological control of air potato (Dioscorea bulbifera) in the southeastern USA. Biocontrol Science and Technology. (33)12:1173-1185. https://doi.org/10.1080/09583157.2023.2294207.
Halbritter, D.A., Kariuki, E., Wheeler, G.S., Rayamajhi, M.B., Minteer, C., Read, Q.D. 2023. Changes in plant architecture in Brazilian peppertree damaged by the biological control agent, Pseudophilothrips ichini Hood (Thysanoptera: Phlaeothripidae). Biological Control. 188. Article c105434. https://doi.org/10.1016/j.biocontrol.2023.105434.