Herbivory by the biocontrol agent Lilioceris cheni suppresses propagule production and smothering ability of the invasive vine Dioscorea bulbifera

Abstract

Expanding populations of Dioscorea bulbifera, a trellising invasive vine of Afro-Asian provenance, have become widely established in the southeastern United States. Its clambering habit enables the weed to grow over, smother and displace native vegetation while producing vast quantities of vegetative propagules (bulbils) and reducing biodiversity of different ecosystems in Florida. A specialized foliage-feeding beetle, Lilioceris cheni from Nepal and China, has been released in USA for biological control of D. bulbifera. To determine the beetle’s potential to curb the vine’s ability to overtop native vegetation and to suppress propagule production, beetle restricted (insecticide treated) and unrestricted (beetle inoculated) sites were compared at five localities in Florida. Dioscorea bulbifera cover, L. cheni population density, and herbivore damage were documented at 6-week intervals, with bulbil density and biomass measured annually, for 5 years. Results from beetle unrestricted treatment revealed that high L. cheni feeding damage reduced vine cover over native vegetation, and decreased bulbil density and biomass. Spillover of L. cheni populations from beetle unrestricted into restricted treatment areas after exhaustion of D. bulbifera vines resulted in coalescing effects between treatments, so the beetle restricted treatment also showed some reduction in vine cover and bulbil density but individual bulbil biomass remained unchanged. These results show that L. cheni has the ability to suppress the invasive attributes of D. bulbifera in its adventive range.