2013 Annual Report
1a.Objectives (from AD-416):
1. To conduct host specificity tests with the beetle Lilioceris egena for possible use as a biological control agent against the invasive Asian vine Dioscorea bulbifera (air potato).
2. To assess impacts of the beetle Lilioceris cheni on populations of air potato in Florida.
1b.Approach (from AD-416):
1. Challenge adult and larval L. egena with potential food resources, including roots, tubers, corms, taproots, bulbs, and rhizomes from a variety of plant species in the Dioscoreaceae and closely related families as food sources.
2. Measure L. cheni impacts on the following parameters: (a) abundance and biomass of existing subterranean tubers of air potato; (b) aerial biomass production, including vine growth and propagule (bulbil) production of air potato; and (c) recovery and maintenance of native plant diversity.
This research relates to in-house objectives: 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.
Dioscorea bulbifera (air potato) is a perennial vine present in nearly every county in Florida. It reproduces vegetatively via persistent subterranean tubers and aerial bulbils that resemble potatoes, hence the common name air potato. This invasive vine can grow more than 20 m before senescing in the fall and is classified as a Category 1 weed by the Florida Exotic Pest Plant Council because of the damage it causes to native plant communities. A classical biological control program against D. bulbifera began after the fortuitous discovery of a Chrysomelid beetle attacking the plant in Nepal in 2002. This leaf-feeding beetle, Lilioceris cheni, proved host-specific to D. bulbifera and USDA-APHIS issued a permit for release in the United States. Subsequent collections were made in China, which yielded L. cheni and a congener, L. egena, which feeds preferentially on bulbils. Open field releases of L. cheni began in 2012. The beetle has tentatively established in several release sites in south Florida. 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 L. egena is underway and preliminary results are encouraging, with a strong preference for D. bulbifera and only test-feeding on the two congeners native to Florida.