Tracking seasonal emergence dynamics of an invasive gall wasp and its associated parasitoids with an open-source, microcontroller-based device

The invasive Asian chestnut gall wasp, Dryocosmus kuriphilus (Hymenoptera: Cynipidae), is one of the most economically important pests of chestnut forest systems. Control is either based on the use of pesticides or the release of the parasitoid Torymus sinensis (Torymidae) for classical biological control of the pest. Both approaches require frequent monitoring of wasp emergence patterns, usually by recording adult emergence from samples of galls stored in dark boxes. Here, we have improved this monitoring method by developing and evaluating a microcontroller-based device. Cages in which galls were placed were modified by insertion of a turntable, which automatically separates wasps emerging at different times. We used this device to monitor the seasonal emergence of D. kuriphilus, its coevolved parasitoid T. sinensis and newly associated native parasitoids from fresh or overwintered chestnut galls formed in 2013 and 2014. In summer, native parasitoids (3.6 and 5.8% of 2-year parasitism) associated with current-year chestnut galls started emerging before the gall wasp and only partially overlapped with D. kuriphilus emergence. After overwintering, in the spring of the following year, T. sinensis (4.3 and 5.5% of 2-year parasitism from overwintered galls) emerged earlier than indigenous parasitoids (1.6 and 4.8%) and indicated potential for D. kuriphilus control. Overall, 14 species of native parasitoids belonging to five families were recorded from fresh and overwintered galls. We provide the schematic and the programming codes for this new device and propose that this automatic device be used to better track the flight periods of D. kuriphilus and its parasitoids.