Preference of Encarsia tricolor for cabbage crops and impact on cabbage whitefly parasitism

Abstract: Plant protection strategies including biological control of the cabbage whitefly
Aleyrodes proletella in field crops are still under development and lack the necessary
effectiveness. The combination of banker plant systems and tailored flower strips could increase this effectiveness. However, it is unclear to what extent the foraging behaviour of the natural enemy Encarsia tricolor is influenced. In this study, we systematically characterized the orientation behaviour of the parasitic wasp through a series of choice experiments conducted in both open field and greenhouse environments. The results suggest that E. tricolor is strongly attracted to cabbage crops, neglecting single flowering plants and flower strips. In a choice trial, 15 times more E. tricolor were found on infested Brussels sprouts compared to flowering Brassicaceae Alyssum maritimum. Under field conditions, the parasitism rate of A. proletella nymphs on trap plants was 12.4 ± 2.6 % compared to 0.6 ± 0.3 % (SE) in the flower strip. However, for this study, E. tricolor was reared on cabbage. It still needs to be studied to what extend the banker plant system with its alternative host Trialeurodes vaporariorum is important for the outcome.