Olfactory responses of Plutella xylostella natural enemies to host pheromone, larval frass, and green leaf cabbage volatiles

Abstract—The parasitoids Trichogramma chilonis (Hymenoptera: Trichogram-matidae) and Cotesia plutellae (Hymenoptera: Braconidae), and the predator Chrysoperla carnea (Neuroptera: Chrysopidae), are potential biological control agents for the diamondback moth, Plutella xylostella (Lepidoptera: Yponomeu-tidae). We present studies on the interactions between these bioagents and var-ious host-associated volatiles using a Y olfactometer. T. chilonis was attracted to a synthetic pheromone blend (Z11–16:Ald, Z11–16:Ac, and Z11–16:OH in a 1:1:0.01 ratio), to Z11–16:Ac alone, and to a 1:1 blend of Z11–16:Ac and Z11– 16:Ald. C. plutellae responded to the blend and to Z11–16:Ac and Z11–16:Ald. Male and female C. carnea responded to the blend and to a 1:1 blend of the ma-jor components of the pheromone, although no response was elicited by single compounds. Among the four host larval frass volatiles tested (dipropyl disul-fide, dimethyl disulfide, allyl isothiocyanate, and dimethyl trisulfide), only allyl isothiocyanate elicited significant responses in the parasitoids and predator, but C. plutellae and both sexes of C. carnea did respond to all four volatiles. Amon