Skip to main content
ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Research Project #441740

Research Project: Establishment and evaluation of Lilioceris egena for air potato biocontrol

Location: Invasive Plant Research Laboratory

Project Number: 6032-22000-013-092-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Aug 16, 2022
End Date: May 31, 2023

This proposal seeks support for the mass production, distribution, and evaluation of a new biological control agent of air potato, the bulbil-feeding beetle Lilioceris egena. We propose to increase our beetle laboratory rearing capacity, release and establish beetles throughout the invaded range, and monitor and examine their impact and safety on the target weed. Our overall goal is a reduction in the competitiveness of air potato in agricultural and natural environments. This will bring about cost-effective, sustainable, and safe control with reduced monetary expenditures and human exposure to herbicides 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) 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; (6) monitor impacts of L. egena on air potato bulbil production and germination at long-term research plots; and (7) Test whether common mosquito pesticides will be as toxic to L. egena as they are to L. cheni.

We will establish long-term monitoring plots at release sites, 3 located in southern Florida and 3 in central/northern FL. Air potato beetle Lilioceris egena adult and larval feeding tunnels are distinct from occasional L. cheni damage to bulbils. This allows us to evaluate L. egena presence by counting numbers of bulbils with tunnels. Monthly censuses will count number of bulbils per square meter and proportion of those bulbils that have feeding tunnels. Number of germinating bulbils and number of vines per square meter will be evaluated quarterly, these metrics are not expected to change as rapidly as number of damaged bulbils. We will monitor plots for 2 years and couple them with assessments of plant status and L. cheni presence to aid understanding of the long-term effects of L. egena on air potato phenology. We will survey within sites and at nearby sites for evidence (damaged bulbils) that the beetles are dispersing. 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. Objecive 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: 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 6: 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 7: We will conduct trials to determine whether common mosquitocides are as deadly to L. egena as they are to L. cheni.