Targeting diamondback moth in greenhouses by attracting specific native parasitoids with herbivory-induced plant volatiles

We investigated whether recruitment of specific parasitoids using a specific blend of synthetic herbivory-induced plant volatiles (HIPVs) could be a novel method of pest control in greenhouses. In the Miyama rural area in Kyoto, Japan,diamondback moth (DBM) (Plutella xylostella) larvae are an important pest of cruciferous crops in greenhouses, and Cotesia vestalis, a larval parasitoid of DBM, are found in the surrounding areas. Dispensers of HIPVs that attracted C. vestalis and honey feeders were set inside greenhouses (treated greenhouses). The monthly incidence of DBM in the treated greenhouses was significantly lower than that in the untreated greenhouses across a two-year period. The monthly incidences of C. vestalis and DBM were not significantly different in the untreated greenhouses, whereas the monthly incidence of C. vestalis was significantly higher than that of DBM in the treated greenhouses. Poisson regression analyses showed that, in both years, a significantly higher number of C. vestalis was recorded in the treated greenhouses than in the untreated greenhouses when the number of DBM adults increased. We concluded that DBM was suppressed more effectively by C. vestalis in the treated greenhouses than in the untreated greenhouses.