BIOLOGICAL CONTROLÐMICROBIALS Susceptibility of the Lesser Peachtree Borer (Lepidoptera: Sesiidae) to Entomopathogenic Nematodes Under Laboratory Conditions

The lesser peachtreeborer, Synanthedonpictipes (Grote andRobinson), is an important pest of Prunus spp.We determined the susceptibility of S. pictipes to six entomopathogenic nematode species:Heterorhabditis bacteriophoraPoinar,H. indicaPoinar, Karunakar andDavid,H.marelatusLiu and Berry, Steinernema carpocapsae (Weiser), S. feltiae (Filipjev), and S. riobrave Cabanillas, Poinar and Raulston. Nematode virulence in S. pictipes was compared with virulence in two known susceptible hosts,Galleria mellonellaL. and Tenebrio molitorL. In S. pictipes, the steinernematids weremore virulent than the heterorhabditids, the virulence of S. carpocapsae was greater than S. riobrave, with S. feltiae being intermediate between the two, and no differences in virulence were detected among the heterorhabditids. Each nematode exhibited similar or greater virulence to S. pictipes than to T. molitor, and the steinernematidsÕ virulence to S. pictipes was greater or similar to H. bacteriophora or H. marelatus virulence in G. mellonella. A quadratic doseÐresponse relationship was detected between S. carpocapsae and S. pictipes, and an LC50 was estimated to be 7.99. Comparisons of steinernematid reproductive potential per host, or per milligram host, generally indicated the highest production in G. mellonella; production in S. pictipes was similar or greater than in T. molitor. In S. pictipes,nodifferences in reproductionweredetected amongnematode species. Basedonour Þndings and other studies on related insect species, we conclude that the prospects for controlling S. pictipes with entomopathogenic nematodes are promising (particularly with S. carpocapsae and S. feltiae), and Þeld testing is warranted.