SYNOMONE-MEDIATED INTERACTIONS BETWEEN THE PARASITOID DIAERETIELLA-RAPAE AND BREVICORYNE-BRASSICAE UNDER FIELD CONDITIONS

An interaction apparently mediated by synomones (Nordlund et al., 1981) between Diaeretiella rapae (M'Intosh), a primary parasitoid and the cabbage aphid, Brevicoryne brassicae (L.), was investigated under field conditions. Direct application of an allylisothiocyanate emulsion at a rate of 0.25 ml per broccoli plant consistently gave higher aphid parasitization rates and/or number of wasps per plant than those observed on plants treated with 0.25 ml of water or with 0.25 ml of wild mustard extract. These results suggest the existence of a synomone-mediated interaction between the species involved, indicating potential avenues to enhance field parasitization rates through manipulation of the chemical environment of cole cropping systems.