The importance of multigeneration host specificity testing: rejection of a potential biocontrol agent of Nymphaea mexicana (Nymphaeaceae) in South Africa

Abstract

Abstract Classical biological control utilizes natural enemies of invasive non-native plants imported from their native range to manage problematic populations. However, a potential biological control agent must undergo strict host specificity tests to ensure that it does not feed on species native to the invaded range. Nymphaea mexicana Zucc. (Nymphaeaceae) is an invasive waterlily in South Africa that is native to the southern USA and parts of Mexico and is a target for biological control in South Africa. The planthopper, Megamelus toddi Beamer (Hemiptera: Delphacidae), is a potential biological control agent that was imported from Florida, USA for host specificity tests under quarantine conditions. Survival and multigeneration trials were carried out to determine the ability of M. toddi to survive and reproduce on its original host, N. mexicana, as well as Nymphaea nouchali Bur. fil., a waterlily native to South Africa, and Nymphaea marliacea var. chromatella Lat.-Marl., a hybrid of N. mexicana. M. toddi was unable to survive for more than two generations on the hybrid but completed three generations on N. nouchali and N. mexicana, indicating that M. toddi is unsafe for use as a biological control agent in South Africa. Nevertheless, the results from this study contribute information about a species that has not been thoroughly studied and emphasizes the importance of conducting thorough host specificity tests before releasing potential biological control agents.