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ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Research Project #440913

Research Project: Release and establishment of the Asian bulbil beetle, Lilioceris egena, a biological control of air potato (Dioscorea bulbifera) in Florida

Location: Invasive Plant Research Laboratory

Project Number: 6032-22000-013-089-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Jul 1, 2021
End Date: Aug 30, 2022

Objective:
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. This project is 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 3: Deploy APHIS-approved biological control agents and evaluate their efficacy by documenting impacts to target weed populations. [C2, PS 2B] The objectives specific to this project are: (1) develop methods for mass-rearing non-quarantine colonies of L. egena (2) conduct field releases of L. egena (3) conduct an ecological host range study (4) monitor release sites to ascertain whether beetles are developing self-persistent populations and to evaluate L. egena efficacy (5) determine whether L. egena will oviposit on bulbils on the vine, or only on post-dehiscent bulbils (6) monitor for L. egena dispersal within release sites, and from release sites to neighboring populations of air potato vine.

Approach:
Objective 1: Multiple colonies (two of insects derived from China, two of insects derived from Nepal) currently contain 100-200 adult beetles each. We are testing various methods for increasing productivity so we have beetles to release at field sites. Objective 2: Field releases will be small (possibly caged) and conducted at a few sites during 2021, then will expand during 2022 once lab colonies show winter reproductive diapause has ended. Initially we plan on releasing larval-infested air potato bulbils at field sites harboring abundant bulbils on the ground. Eventually, we will likely release adults as well. Objective 3: Open-field host-specificity testing helps describe the ecological, or realized host range, which is frequently more restrictive than the physiological host range because it incorporates host searching and recognition behaviors that are bypassed in laboratory-based host range trials. The most important species to test in ecological host range trials generally are congeners of the target weed so we have maintained a half-dozen of each Dioscorea spp. from the physiological host range trials to use in the proposed open-field trials. This trial will follow the methods of Lake et al. 2015. Objective 4: We will establish long-term monitoring plots at several release sites in southern Florida and several more in central/northern Florida. L. egena adult and larval feeding tunnels are distinctly different from occasional L. cheni damage to bulbils. This will allow us to evaluate L. egena presence by counting numbers of bulbils with tunnels. Monthly censuses will count the numbers of bulbils per square meter and the proportion of those bulbils that have feeding tunnels. Two additional metrics, the number of germinating bulbils and vines per square meter will be evaluated on a quarterly basis. Objective 5: We propose to cage vines dcage vines developing on outdoor trellises at our facility, release L. egena adults into the cages and monitor the bulbils on those vines for L. egena eggs, larval development and premature abscission of the bulbils. Bulbils that are damaged but complete development will be harvested and potted to monitor for germination. These latter will be compared to germination rates of similar, undamaged bulbils from trellises outside the cages.