Enhancing biological pest control: olfactory conditioning of parasitoid wasps

Abstract: Parasitoid wasps are used in biological control programmes to supress pest
populations below economic thresholds but can be slow to establish following release. Slow
establishment may, in part, be a result of current mass-rearing systems that do not account for how cognitive processes such as learning can affect host location and recognition. This study examined whether naive Diaeretiella rapae M’Intosh (Hymenoptera: Braconidae) wasps associated the aphid host/plant system in which they were reared with future oviposition choices and whether the aphid host or aphid host plant had a greater influence on choices made. To achieve this, wasps were reared on two different systems: (1) Brevicoryne brassicae (Hemiptera: Aphididae)/Pak choi (Brassica rapa subsp. chinensis var. ‘Hanakan’) or (2) Myzus persicae (Hemiptera: Aphididae)/Pak choi (var. ‘Hanakan’), and their oviposition preferences were tested on four different combinations of the same or different aphid host, on the same or different plant. Results from wasps reared on system (1) suggest that the aphid host was the primary factor influencing the number of parasitoid mummies produced, whereas for wasps reared on system (2) both aphid host and plant influenced parasitisation. Further research is needed to evaluate how wasp rearing systems can affect parasitisation efficacy upon releases of biological controls into crops.