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 b iological control of purple loosestrife, Lythrum salicaria. We tested the h ost specificity of G. calmariensis against 40 nontarget species in 14 previ ously untested families, determining the ability of G. calmariensis adults to survive, feed, produce eggs, and oviposit on these plants in no-choice t ests. When adult feeding occurred, we then tested the potential for adult a nd 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 f or 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 fasic ulata (Asteraceae) and five members of the Rosaceae, subfamily Rosoideae, F ragaria x. ananassa, Filipendula rubra, Rosa setigera, Alchemilla mollis, a nd Rubus idaeus. In subsequent choice tests, oviposition never occurred on nontargets and no-choice larval establishment tests showed that neonates co uld not establish on any of these species. For F. rubra, which may potentia lly co-occur with L. salicaria, no-choice larval transfer trials showed tha t 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 supp ort preintroduction host specificity results indicating that normal feeding , oviposition, and development of G. calmariensis is confined to L. salicar ia. However, recent held observations confirm the greenhouse studies indica ting that transient feeding by teneral adults may occur on some nontargets under no-choice conditions. (C) 2000 Academic Press.