Laboratory rearing of Lytopylus rufipes (Hymenoptera: Braconidae: Agathidinae), a parasitoid wasp of the oriental fruit moth, Grapholita molesta (Lepidoptera: Tortricidae), using apple and a commercially available diet

Abstract

Lytopylus rufipes (Nees) (Hymenoptera: Braconidae: Agathidinae) is a potential natural enemy of the oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), but there is no established method to rear this wasp continuously. In the laboratory, female wasps can produce both female and male progenies without mating (deuterotokous), but host-infested plants are necessary to trigger oviposition behavior. In this study, immature apples were used because they keep well. Grapholita molesta larvae were transferred to immature apples, and then exposed to L. rufipes females. After parasitization, these apples were transferred to blocks of artificial diet (Silkmate 2M) for further rearing. Using this transitional diet system, L. rufipes females develop in 25.1 ± 1.8 (mean ± SD) days from egg to adult, but male wasps require only 23.8 ± 1.0 days. Furthermore, the longevity of female wasps was 12.2 ± 7.3 (mean ± SD) days, and the parasitism rate was 26.4 (95% Cl: 22.2–30.6). Female wasps can attack host larvae in all instars, but parasitism of first-instar larvae is more successful. Therefore, first-instar larvae of G. molesta are recommended for establishing a L. rufipes colony under laboratory conditions. This system decreases the requirement for plant material and maintains continuous production of L. rufipes.