Response of Lilioceris cheni to herbivore induced plant volatiles from Dioscorea bulbifera

Abstract

Insect damage to a plant activates induced defenses, which include releases of herbivore induced plant volatiles (HIPVs) that attract natural enemies and usually repel generalist herbivores. Oppositely, most herbivore specialists have evolved responses against these defenses, and in many cases are attracted to host HIPVs. However, it is not clear if a specialist is able to discriminate HIPVs released by conspecifics, other specialists, or generalist damage. Dioscorea bulbifera is an invasive vine native to Asia and Africa with infestations in the southeastern United States, Hawai’i, and Puerto Rico. A host specific biological control agent, Lilioceris cheni (Coleoptera: Chrysomelidae) was introduced in 2011 to control D. bulbifera. Recently, a new host specific biological control agent, Lilioceris egena, has been released to improve the biological control program for D. bulbifera. In this study, attraction of L. cheni to HIPVs from generalist, Spodoptera frugiperda (Lepidoptera: Noctuidae); specialist, L. egena; and conspecific damage were investigated. Behavioral assays indicated L. cheni had preference for any type of herbivore damaged plants compared to undamaged plants and discriminated between conspecific damaged plants in the presence of generalist damaged plants, favoring conspecific damaged plants. Differently damaged D. bulbifera plants were then evaluated using gas chromatography coupled with mass spectroscopy which revealed significant quantitative differences between both the specialists’ herbivore damage compared to the generalist volatile profiles with induction of 11 volatiles and suppression of four. This study highlights the importance of understanding an invasive plant’s response to specialist and generalist damage for better management of the invasive species.