Oviposition preferences of the oriental fruit moth Grapholita molesta (Lepidoptera: Tortricidae) to pear HIPVs

Abstract

Herbivore-induced plant volatiles (HIPVs) are regarded as an indirect plant defense against herbivores, since they attract natural enemies to infested plants. On the other hand, HIPVs also affect behavioral responses of herbivores. In a previous study, Lytopylus rufipes, a parasitoid of the oriental fruit moth (Grapholita molesta), showed positive responses to pear HIPVs, but the influence of pear HIPVs on G. molesta is still unclear. To better understand these responses, we first tested oviposition preferences of G. molesta to uninfested and infested pear shoots (US and IS, respectively) and uninfested mature leaves (ML) in dual-choice bioassays using a cylindrical tube. Then, preferences to volatile components were also assessed. G. molesta females preferred US-, IS-, and ML-treated areas compared to the control area (no leaves), respectively. Subsequently, G. molesta females preferred IS over US, and US more than ML in bioassays. Furthermore, G. molesta females did not show any significant preference for individual volatile components, but more eggs were laid in an area treated with a synthetic pear HIPV blend, compared to the hexane-treated area (control). These results indicate that G. molesta females do not avoid infested pear shoots nor HIPVs. Moreover, HIPVs may recruit not only natural enemies, but also G. molesta females to the release point of HIPVs. Thus, it is important to examine responses of G. molesta females to HIPVs in the field before employing them for pest management.