Location: Invasive Plant Research Laboratory2013 Annual Report
1a. Objectives (from AD-416):
1. As new high-priority invasive species are detected in the U.S., conduct feasibility studies to determine their suitability for biological control. 2. 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. 3. Conduct faunistic and floristic inventories to discover natural enemies that may serve as biological control agents for target weeds including, but not limited to Brazilian pepper, lygodium, downy rose myrtle, skunk vine and Chinese tallow. Additional biological control agents will be sought for species for which some control has been achieved, including melaleuca. 4. Conduct risk analysis to determine environmental safety of new and existing potential biological control agents for weeds such as air potato, melaleuca, Brazilian pepper, lygodium, downy rose myrtle, Chinese tallow, waterlettuce and skunk vine. 5. Release, establish, evaluate efficacy, and corroborate environmental safety of approved biological control agents and develop and distribute the technology to customers in order to expedite their adoption and deployment.
1b. Approach (from AD-416):
Survey foreign nations for potential biological control agents, determine host specificity of candidate species, release approved agents into natural and agricultural ecosystems, and evaluate influence of agents on target weed and nontarget species population dynamics. Study molecular genetic target weeds. Study their roles as insect feeding attractants/deterrents, effects on biological control agents' nutritional and reproductive physiology, and possible use in host specificity protocols. Study biological control agents' impact on competition between target weeds and non-target native plants. Identify ways to incorporate biological control agents into IPM strategies. Survey water bodies in Connecticut for presence of troublesome aquatic weeds.
3. Progress Report:
The flea beetle Bikasha collaris (Chrysomelidae) exhibits a high degree of specificity for the target weed Chinese tallow (Triadica sebifera). No choice and dual choice tests for B. collaris larvae and adults as well as oviposition tests are complete. There is strong evidence that B. collaris will not sustain successive generations on any non-target species. Scientists have established field plots for Chinese tallow in order to evaluate the population dynamics of this invasive tree. This information will be used to evaluate the impacts of biological control agents once they are developed and released. Scientists are processing the last sample from a six year chronosequence study comparing the decomposition dynamics of Melaleuca quinquenervia and Pinus elliotti logs in a western Everglades site in order to examine mass loss, nutrient concentrations, and invertebrate abundance and diversity. Final assessments were made in a 16 year study that elucidates the influence of biological control on Melaleuca and the return of native species following density reductions of the exotic weed. A study was initiated at the A.R.M. Loxahatchee National Wildlife Refuge evaluating the impact of biological control on Melaleuca as well as the impact of herbicide operations. Megamelus scutellaris is the first new biological control agent released against waterhyacinth in more than 30 years. In Florida, field establishment and evaluation sites have been monitored since 2010. Starter colonies of M. scutellaris have been sent to two state agencies, one university, and two federal agencies operating in Florida, California, Louisiana, and Mississippi. The insect has overwintered in multiple locations in Florida as far north as Gainesville. Open field releases of the air potato beetle Lilioceris cheni continued in 2013. Despite relatively small releases, large populations built up in the field and caused premature die back of air potato vines and reduced bulbil production in some sites. Host specificity testing of another air potato biological control agent, Lilioceris egena, is underway and preliminary results are encouraging, with a strong preference for D. bulbifera and only test-feeding on a few congeners native to Florida and the Caribbean. Both Lilioceris species have been characterized by molecular taxonomy. The Lygodium microphyllum biological control agent Neomusotima conspurcatalis continues to increase its range and has dispersed beyond initial predictions. Scientists discovered that persistent feeding by Austromusotima camptozonale on aerial plant parts can kill the invasive fern L. microphyllum, including perennial rhizomes. Additionally, the Lygodium gall mite, Floracarus perrepae, was discovered in areas well beyond the established release sites. Within quarantine, host range testing of the Lygodium herbivores, Lygomusotima stria and Neostrombocerus albicomus are ongoing. Critical test plants were acquired in 2013 by ARS scientists, including Lygodium volubile and L. micans from Jamaica, which will be used in host range testing and molecular barcoded.
1. Discovery and testing of a new agent for biological control of the weed, Chinese tallow, Triadica sebifera. Chinese tallow is a weed of coastal prairies and forests in the southeastern U.S. Current management tactics, such as chemical and mechanical controls, are not sustainable solutions considering that Chinese tallow grows rapidly and produces a large number of seeds annually. Biological control is a permanent and cost-effective alternative means of Chinese tallow suppression. Surveys conducted in China discovered a promising caterpillar, Gadirtha n. sp. that is being tested for biological control of this invasive weed. Results show this insect completed development only on the target weed when tested in quarantine. These results indicate that this potential biological control agent shows promise for safe control of this weed in the U.S.
2. Importation, colonization, evaluation, and consignment of a new biological control agent ecotype for waterhyacinth. ARS researchers at Ft. Lauderdale, Florida and Argentinean scientists from Fundacion para el Estudio de Especies Invasivas searched for ecotypes of Megamelus scutellaris in several South American countries in order to obtain better climatic matches for environments across North America with infestations of waterhyacinth. Several populations were collected, shipped, analyzed for molecular variation, colonized, tested, and then deployed in the U.S. to increase the effectiveness of this permitted agent against the world's worst aquatic weed.
Boughton, A.J., Kula, R.R., Gates, M.W., Zhang, Y., Nunez, M., O'Connor, J., Whitfield, J.B., Center, T.D. 2012. Parasitoids attacking larvae of a recently introduced weed biological control agent, Neomusotima conspurcatalis Warren (Lepidoptera: Crambidae): key to species, natural history, and integrative taxonomy. Annals of the Entomological Society of America. 105:753-767.