Location: Invasive Plant Research Laboratory
Project Number: 6032-22000-013-116-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Jun 9, 2023
End Date: May 31, 2024
Objectives are to (1) Maintain laboratory colonies of the air potato biological control agent, L. egena; (2) Develop methods to optimize L. egena non-quarantine colony production; (3) Investigate methods for most efficiently conducting field releases of L. egena; (4) Determine whether L. egena will oviposit on bulbils on the vine, or only post-dehiscent bulbils; (5) Determine whether releasing both Nepalese and Chinese L. egena will be detrimental, beneficial, or neutral, in terms of reproductive success and longevity; (6) Monitor for establishment of persistent L. egena populations within release sites, dispersal within release sites, and dispersal from release sites to neighboring populations of air potato vine; (7) Validate physiological host range data used in acquiring release permit by conducting ecological host range study (similar to what was done with L. cheni); and (8) Test whether common mosquito pesticides will be as toxic to L. egena as they are to L. cheni.
Objective 1: Laboratory colonies of the air potato beetle L. egena will be maintained at the USDA/ARS Invasive Plant Research Lab (IPRL) in Fort Lauderdale, and the Florida Division of Plant Industry in Gainesville. Rearing of this biological control agent has previously been completed using field-collected bulbils. This method will predominate as new rearing methods are being developed and field populations are being established. Objective 2: Collecting sufficient numbers of bulbils during late fall/winter is labor intensive and creates problems of adequate storage (about 750 bulbils each year must be stored in the dark at 10°C to prevent germination). One way to avoid the need for collecting bulbils every year would be to grow our own, so we will investigate methods (e.g., artificial lighting regimes; supplementing plant hormones, like cytokinins and auxins, associated with bulbil formation) of stimulating cultivated vines to produce bulbils “out-of-season” to provide food resources for the mass rearing efforts. Objective 3: We will investigate infesting bulbils with known numbers of larvae, then depositing these larval-infested “bulbil bombs” at field sites. This will let larvae complete development in the bulbil and pupate in the local soil, thus imprinting on the local habitat. We will also test adult releases. Objective 4: We will investigate whether L. egena will feed and oviposit in bulbils growing on the vine, rather than just on dehiscent bulbils. Objective 5: Two biotypes of L. egena, acquired from significantly different centers of origin, were included in the host range trials and have been approved for release. We intend to conduct hybridization studies, crossing the pure lines and the resulting F1 generations, and then monitoring the F2 progeny for pupation success, female fecundity, and life spans as a means of determining whether or not we should release both strains in Florida. Objective 6: We will assess the minimum threshold for establishment and measured dispersal of L. egena both within release sites (i.e., moving out from release points to surrounding parts of the air potato population) and from release sites to nearby air potato infested sites. Objective 7: We intend to establish three long-term monitoring plots in southern Florida and three in central/northern Florida where we will monitor bulbil production, % damaged bulbils, and bulbil germination as metrics of agent success. Objective 8: We will conduct field trials to compare the ecological host range to the physiological host range determined in the lab. Objective 9: We will conduct trials to determine whether common mosquitocides are as deadly to L. egena as they are to L. cheni.