Efficacy of the entomopathogenic nematodes on pupal stage of the Oriental fruit moth, Grapholita molesta (Lepidoptera: Tortricidae) and Codling moth, Cydia pomonella (Lepidoptera: Tortricidae).

Abstract

Oriental fruit moth Grapholita molesta (Lepidoptera: Tortricidae) and codling moth, Cydia pomonella (Lepidoptera: Tortricidae) are serious pests of temperate fruit trees such as peach, pear and apple. Control of pupae would reduce or eliminate damage to fruit caused by subsequent generations. The objective of this study was to evaluate the effectiveness of commercially available entomopathogenic nematodes (EPNs) against pupae of G. molesta and C. pomonella under laboratory conditions. In a preliminary assay, a series of application rates of Steinernema carpocapsae and Steinernema feltiae were used against pupae, and on the basis of the results, we selected an application rate of 5,000 infective juveniles/insect to determine the EPN virulence. Due to limited availability of insects, we conducted two rounds of fully replicated virulence experiments. In virulence test in round 1, we tested S. carpocapsae, S. feltiae, and Heterorhabditis bacteriophora against G. molesta and C. pomonella pupae. In round 2, S. carpocapsae was considered a standard (based on the results of round 1 test) and was included with three other species of EPNs: Steinernema riobrave, Steinernema glaseri, and Heterorhabditis indica. Results indicated that all EPNs tested were pathogenic and caused higher mortality than the non-treated control. The highest pupal mortality (60-80%) against both insects at 3 days posttreatment was observed for S. carpocapsae treatments compared with other treatments in both rounds of tests. In conclusion, EPNs have potential to be applied to G. molesta and C. pomonella pupae to efficiently reduce fruit damage and pest populations in the subsequent growing season. Future studies will need to explore the use of EPNs against G. molesta and C. pomonella pupae under different/natural environmental conditions within orchard agroecosystems.