Host specificity testing of Galerucella calmariensis L. (Coleoptera: Chrysomelidae) on wild and ornamental plant species

Galerucella calmariensis has been widely distributed in North America for biological control of purple loosestrife, Lythrum salicaria. We tested the host specificity of G. calmariensis against 40 nontarget species in 14 previously untested families, determining the ability of G. calmariensis adults to survive, feed, produce eggs, and oviposit on these plants in no-choice tests. When adult feeding occurred, we then tested the potential for adult and larval impacts in a series of choice and no-choice tests. For nontarget plants that may co-occur with L. salicaria, we also tested the propensity for larval and adult attack under conditions of high G. calmariensis density. In no-choice adult feeding tests, G. calmariensis did not feed or survive on most of the species tested. Minor damage was observed on Vernonia fasiculata (Asteraceae) and five members of the Rosaceae, subfamily Rosoideae, Fragaria x. ananassa, Filipendula rubra, Rosa setigera, Alchemilla mollis, and Rubus idaeus. In subsequent choice tests, oviposition never occurred on nontargets and no-choice larval establishment tests showed that neonates could not establish on any of these species. For F. rubra, which may potentially co-occur with L. salicaria, no-choice larval transfer trials showed that third instar G. calmariensis larvae did not feed on F. rubra and pupated at significantly reduced weights. In a large-cage choice study with larvae and adults, no feeding or oviposition on F. rubra occurred. These data support preintroduction host specificity results indicating that normal feeding, oviposition, and development of G. calmariensis is confined to L. salicaria. However, recent held observations confirm the greenhouse studies indicating that transient feeding by teneral adults may occur on some nontargets under no-choice conditions. (C) 2000 Academic Press.