Keeping a close eye on the searching behaviour of the mass-reared parasitoid Dichasmimorpha longicaudata: addressing a standardised test

Abstract

ABSTRACT Tephritid fruit flies are responsible for many losses in the fruit market due to direct damage to fruits and their quarantine restrictions. Augmentative parasitoid releases are an effective method of biological control that is complementary to the sterile insect technique (SIT) currently used for the management of many tephritid species. However, mass-produced parasitoids must exhibit high-quality attributes that are crucial for the reduction of pest populations. Females must be able to disperse and locate host larvae following kairomones. Nevertheless, there is currently no standardised, fast-processing method to assess the quality of searching parasitoids. Since parasitoid effectiveness is linked to flight ability, we developed a test with a larval-odour device that aimed to measure the quality of female parasitoids via their ability to locate host larvae by their odour. As an odour source, we applied a used or clean artificial host diet on a 3 × 2 cm piece of filter paper. We diluted the diets in ethanol at 1/1, 1/2, 1/3, and 1/4 (% mass/vol) to obtain an odour gradient. Female wasps landed and attempted to oviposit more frequently on devices treated with used diet than on those treated with clean diet. We suggest that this test can be implemented as a simple and fast method to evaluate the searching behaviour of mass-reared parasitoids of fruit fly larvae.