Preparing for release of the Asian leaf beetle, Lilioceris egena, a biological control of air potato (Dioscorea bulbifera) in Florida

Authors: Dray, F Allen; Goldstein, Scott; Rayamajhi, Min; Tipping, Philip

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/23/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary: Air potato is a climbing vine that climbs over trees and shrubs in native Florida habitats, displacing native species and disrupting native plant communities. It does not produce seeds in Florida, but reproduces by tubers (called bulbils) that grow in the leaf axils (where the leaf attaches to the vine). An Asian leaf-feeding beetle, Lilioceris cheni, has been released in Florida to control air potato and is causing reductions in vine height, slowing growth, and reducing bulbil production. However, bulbil production has not been eliminated and new plants grow from these bulbils each spring. We have been studying a second species of beetle, Lilioceris egena, for possible release as another control for air potato. This beetle prefers to feed and lay its eggs on the bulbils. The damage thus produced is likely to reduce the numbers of bulbils that can germinate to produce new plants each spring. Our studies have shown that the beetle will only survive on air potato, and a petition has been sent to regulatory agencies for permission to release this insect in Florida. The regulatory process is ongoing and can sometimes take several years. In the meantime, we are maintaining colonies of L.egena and conducting small studies to better understand the beetle/bulbil interactions.

Technical Abstract: Air potato, Dioscorea bulbifera L., (Dioscoreaceae) is an herbaceous, perennial vine with alternate, heart-shaped leaves. It rarely flowers in the U.S. and reproduces exclusively through aerial tubers, called bulbils, which form in the leaf axils and abscise as the plant senesces in the fall. The Florida Exotic Pest Plant Council (FLEPPC) has listed air potato as a Category I weed because it displaces native plants, changes plant community architecture, and alters ecological function. Lilioceris cheni Gressitt & Kimoto (Coleoptera: Chrysomelidae) is a host-specific Asian beetle that feeds voraciously on air potato leaves. Releases of this beetle over the past 7 years have led to reduced air potato densities. However, plant population regrowth is still promoted via production of bulbils, albeit these are now fewer, and smaller, than prior to L. cheni release. Another Lilioceris species, L. egena Weise (collected in China during May 2011) preferentially attacks air potato bulbils, which do not sprout if their meristematic tissue is damaged. During 2012-2017, we conducted 2,857 host range trials showing that this beetle has complete fidelity to air potato. A petition requesting permission to release L. egena in Florida was submitted to the U.S.D.A. Animal and Plant Health Inspection Service (APHIS) Technical Advisory Group on Biological Control of Weeds (TAGBCW) in November 2017. On 30 March 2018, the TAGBCW recommended this insect be approved for release in the U.S. APHIS has accepted this recommendation and is currently pursuing the formal regulatory process required to grant final permission to release. This process can take up to two years, during which we are maintaining the insect colonies, maintaining cultures of Dioscoreaceae plants for use in post-release field-based ecological host range studies, and conducting research to better understand beetle/bulbil interactions.