Skip to main content
ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Research Project #439299

Research Project: Development and Implementation of Biological Control Programs for Natural Area Weeds in the Southeastern United States

Location: Invasive Plant Research Laboratory

2022 Annual Report

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]

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
Invasive weeds are one of the leading causes of habitat loss and dramatically disrupt ecosystem services. In sensitive ecosystems such as Florida’s Everglades, the harms brought about by invasive species can exacerbate stressors caused by climate change and development, leading to species declines and even extinctions. Biological control is one of the most cost effective means of controlling invasive species with an expected return on investment in excess of 35:1 in successful programs. The Invasive Plant Research Laboratory in Fort Lauderdale, Florida has several recent and historical examples of successful biological control programs that have reduced cover, reproduction and the negative impact from invasive species (e.g., melaleuca, air potato, alligator weed, common salvinia, etc.). Below, find examples of our progress in the last fiscal year towards restoring America’s largest wetlands from the impacts of harmful plant invasions. Melaleuca quinquenervia is an evergreen tree, that once infested about 800 square miles. Melaleuca outcompete native plants, eliminate animal habitats, increase fire severity, disrupt nutrient storage and cycling, and affect human health. Biological control developed by ARS researchers in Fort Lauderdale, Florida has transformed this plant so that it no longer dominates the landscape and is now much easier to control using conventional methods. A release permit for the latest agent, L. indentata was issued in March 2022. We are currently in talks with several Florida land management agencies to obtain permission to release and long-term monitor populations. Additionally, we are ramping up plant production to begin a mass rearing and release project with this agent. This research will include food web studies, ecological impact studies, and niche studies to look at the in-situ interaction between L. indentata and the other melaleuca biological control agents. Old World climbing fern, Lygodium microphyllum, negatively impacts a myriad of communities in The Everglades and peninsular Florida. In FY22, 360,000 brown lygodium moths (Neomusotima conspurcatalis) and 14.5 million 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. Multi-year, multi-site research is quantifying the damage these agents cause to lygodium in the field both on their own and as part of an integrated weed management strategy. New biological control agents for lygodium continue to be developed including two leaf feeding moths, a sawfly, and four species of stem borers. We plan to petition for the release of two of these agents: Lygomusotima stria and Callopistria exotica. Both species show a high level of host-specificity in no-choice quarantine tests. We are currently focused on determining environmental limits for survival and reproduction. Chinese tallow, (Triadica sebifera), is an invasive tree that has invaded about 500,000 acres of southern U.S. forests, reducing timber yields and habitat. The Technical Advisory Group (TAG), USDA-APHIS, and U.S. Fish and Wildlife Service (USFWS) approved the release of the biological control agents, the flea beetle (Bikasha collaris) and the moth Gadirtha fusca. Currently we are waiting for USDA-APHIS to issue a release permit. Research to maximize agent production indicated that potting media affects rearing success of the root feeding flea beetle, B. collaris. Rearing conditions for G. fusca, including survival, development rate, pupal weights, and fecundity were greatest at 25 degrees Celsius temperature. Diapause in G. fusca larvae was induced by short photoperiod resulting in greater pupal weights and slower development rates. Brazilian peppertree (BP), Schinus terebinthifolia is one of the most invasive weeds in southern Florida, occupying over 700,000 acres and displacing native plant communities from ecologically sensitive areas. Biological control is expected to provide land managers with a cost-effective, self-sustaining means of controlling BP. The newly implemented mass rearing project with the thrips, Pseudophilothrips ichini for the biological control of BP continues to expand. Since permitted, we have released over 2 million thrips at 561 locations. Preliminary surveys recovered thrips at 35-60% of the sites at 61-90 days after release. These thrips are foliage feeders but we found them also causing considerable damage to reproductive tissues causing direct reduction in the weed’s reproduction. Food web studies to examine community-wide impacts have been concluded. Three semi-permanent long-term field research sites have been established aiming at representing the north-south distribution range of BP in Florida. Food-web studies after one year of thrips releases did not show any increase in the native arthropod predator community (e.g., spiders and ants), an indication that the thrips will not provide a subsidy to predators. Waterhyacinth, Pontederia crassipes, often described as the world’s worst weed, damages ecosystems, economies, and even public health 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 Florida. Mass rearing has been scaled back, but we are currently engaged in an areawide research project to determine optimal strategies for integrating biological control into large-scale weed management for Waterhyacinth. This research is focused on field sites on Lake Okeechobee. Our work in the community mesocosms confirmed previous work that the inclusion of herbivores with a chemical control strategy increases the efficacy and longevity of herbicidal control. It also decreases the non-target impacts on the native community. Work in Argentina at Fundación para el Estudio de Especies Invasivas (FuEDEI) is currently underway to investigate the feasibility of an additional agent, Thrypticus truncates. Waterlettuce, Pistia stratiotes, is a serious floating weed of the southeastern U.S. In 2022, Genetic research comparing worldwide populations of this weed have concluded that there are at least seven distinct clades, three of which may possibly be new cryptic species. One of these appears to be native in countries bordering the Caribbean (including Florida), and another may be more broadly native throughout the Americas (including portions of U.S. Gulf Coast). This discovery led us to abandon pursuing the Argentine planthopper Lepidelphax pistae in the U.S. because it is not genotype specific and attacks all waterhyacinth in Florida. We are currently conducting mesocosm studies to investigate the efficacy of various IPM approaches using native herbivores and herbicides. Air potato (Dioscorea bulbifera) vine has spread throughout public and private forested properties in all 67 Florida counties and in other adjacent states. The Invasive Plant Research Laboratory in Fort Lauderdale, Florida has developed two genotypes (Nepalese and Chinese) of the beetle Lilioceris cheni that feeds only on air potato leaves and vine-tips. In FY 2021, all mass rearing and release of L. cheni was transferred to Florida Department of Agriculture & Consumer Services. Focus of the project has now shifted to another agent, Lilioceris egena, which feeds and develops on vegetative propagules (called bulbils). Following Animal and Plant Health Inspection Service approval (March 2021), mass rearing has resulted in 7500 beetles released at over 60 sites. 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. Calomela intermerata is currently undergoing host range evaluation, biology studies, and impact assessments. Thus far, more than 50 species have been cleared and we have observed no feeding or development on any non-target species. Additionally, Trichilogaster was imported into the Fort Pierce quarantine and colonies are thriving. We anticipate receipt of a colony once quarantine repairs are finished. Temperature dependent development and reproduction studies are now underway with the Queensland and Northern Territory genotypes of C. intemerata. Casuarina species, or Australian pine, are fast growing evergreen trees that have become serious invasive weeds of agricultural, urban, and coastal areas in the US especially in southern Arizona, California, Florida, Hawaii, and Texas. With their shallow root system, they are prone to fall during extreme wind events causing economic damage to agriculture, homes, and businesses. Casuarina leaf litter leaches toxic substances that preventing germination. When flowering, people suffer from allergic reactions to the abundant amounts of pollen produced seasonally. Biological control is being examined with the USDA-Australian Biological Control Lab which has discovered and prioritized several potential agents including gall inducing wasps, Selitrichodes spp, seed feeders Bootanelleus orientalis and Dasineura sp., defoliating moths, Cryptophasa irrorata, and Calathusa maritime, and a cecidomyiid tip gall midge Ophelmodiplosis clavate.

1. Release of the air potato beetle, Lilioceris egena. Air potato (Dioscorea bulbifera) is a subtropical Old World vine that has become invasive along the Gulf Coast, especially in Florida. ARS researchers at Fort Lauderdale, Florida, received a permit to release the beetle Lilioceris egena in the U.S.: this beetle feeds only on air potato and specializes on the reproductive bulbils (‘potatoes’). Despite slowed growth and bulbil production caused by a previously released Asian beetle (Lilioceris cheni), stakeholders face significant infestations resulting from germination of those bulbils still being produced. By attacking these bulbils, L. egena will significantly impede population regrowth allowing native species to reclaim stakeholder lands currently covered by air potato.

2. New Biological Control Agent for Melaleuca quinquenervia. Host range testing by ARS researchers at Fort Lauderdale, Florida indicated the leaf-galling midge, Lophodiplosis indenta will be safe for release. This release was recommended by TAG and U.S. Fish and Wildlife Service, and a release permit was issued by the USDA APHIS. These biological control agents may provide land managers additional control for recalcitrant melaleuca infestations in perennially wet areas.

Review Publications
Stewart, H.A., Janiak, D.S., Wright, J.L., Hunt, D., Carmona Cortes, A., Powell, K.T., Chapman, L.J., Altieri, A.H. 2022. Epibiont community composition of red mangroves Rhizophora mangle are contingent on root characteristics. Marine Ecology Progress Series. 686:15–35.
Jones, I.M., Madeira, P.T., Blair, Z.J., Lake, E.C. 2021. Using molecular gut content analysis to identify key predators in a classical weed biological control system: a study with Neomusotima conspurcatalis (Lepidoptera: Crambidae). Biocontrol. 66:825–836.
Madeira, P.T., Dray Jr, F.A., Tipping, P.W. 2022. The phytogeography and genetic diversity of the weedy hydrophyte, Pistia stratiotes L. Biological Invasions. 60(5):685–69.
Smith, M.C., Lake, E.C., Wheeler, G.S. 2016. Oviposition preference by Neomusotima conspurcatalis, a biological control agent for the invasive fern, Lygodium microphyllum. Entomologia Experimentalis et Applicata. 160(1):11-17.
Smith, M., Pratt, P.D., Rayamajhi, M.B. 2022. Crown area predicts total biomass for Rhodomyrtus tomentosa, an invasive shrub in Florida. Invasive Plant Science and Management. 15(1):61-66.
Wheeler, G.S., Kendra, P.E., David, A.S., Lake, E.C., Sigmon, J., Palacios, J.N. 2021. Community of bark and ambrosia beetles (Coleoptera: Curculionidae) infesting Brazilian peppertree treated with herbicide and the volatile tree response. Environmental Entomology. 50(6):1311–1321.
Hoddle, M., Lake, E.C., Minteer, C., Daane, K. 2021. Importation Biological Control. In: Mason, P.G. Biological Control: A Global Endeavour. First Edition: CSIRO Publishing. 67-89.
Hogg, B.N., Stokes, K.H., Rayamajhi, M.B., Geiger, J., Pratt, P.D. 2020. Foliar lifespan, phenology and seasonal dynamics of the invasive shrub Schinus terebinthifolia. Invasive Plant Science and Management. 60(3)212-220.
Hadish, J., Biggs, T., Shealy, B., Bender, M.R., McKnight, C., Wytko, C., Smith, M., Feltus, A.F., Honaas, L.A., Ficklin, S. 2022. GEMmaker: Process massive RNA-seq datasets on heterogeneous computational infrastructure. BMC Bioinformatics. 23. Article 156.
Wheeler, G.S., Jones, E., Fung, J., Fernandez-Triana, J., Vitorino, M., Mckay, F. 2022. Predicting parasitoid accumulation of potential Brazilian peppertree biological control agents from assessments in the native and invaded ranges. Biological Control. 173.
Foley Iv, J.R., Salom, S.M., Barney, J.N., Lakoba, V.T., Brooks, R., Fletcher, R., Heminger, A., Maynard, L., Mcelmurray, P., Haak, D.C., Sharma, G., Seo, H. 2022. Transformative learning in graduate global change education drives conceptual shift in invasive species co-management and collaboration. Environmental Education Research.
Halbritter, D.A., Rayamajhi, M.B., Wheeler, G.S., Leidi, J.G., Owens, J.R., Cogan, C.A. 2021. Advances in mass rearing Pseudophilothrips ichini (Hood) (Thysanoptera: Phlaeothripidae), a biological control agent for Brazilian peppertree in Florida. Insects. 12(9):790.