Effects of Conspecific Herbivory and Mating Status on Host Searching and Oviposition Behavior of Plutella xylostella (Lepidoptera: Plutellidae) in Relation to Its Host, Brassica oleracea (Brassicales: Brassicaceae)

Abstract

Knowledge of host chemical volatiles has tremendously informed the fundamental understanding of plant-insect interactions as well as revealed opportunities for the creative use of plant-derived chemicals in the food and flavor industries and in insect pest management. This study was undertaken to assess the host searching behaviors of diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae) females in relation to their mating status and conspecific larval herbivory. This involved measurement of odor-modulated upwind flight of female moths in a wind tunnel. Subsequently, the host location, recognition and acceptance behaviors of gravid females in relation to either intact uninfested or larvae-infested cabbage, Brassica oleracea L. (capitata group; Brassicales: Brassicaceae) hosts were compared in no-choice and dual-choice tests. Mating status had little effect on the female responses to host odor and flight duration. However, female moths were significantly more attracted to conspecific larvae-infested cabbage plants and had significantly shorter flights than in relation to intact uninfested cabbage hosts. Behavioral responses of gravid females were consistent when offered intact and larvae-infested cabbage hosts in both no-choice and choice tests in observation cages. Antennal rotation and ovipositor probing were found to be important in host searching and recognition, respectively, before a host was accepted for egg laying. Female moths oviposited significantly more eggs on larvae-infested cabbage than on intact uninfested cabbage and in particular more on leaves than on other parts of the cabbage plant. These results indicate the potential of developing a brassica host-derived kairomone attractant as a useful monitoring tool for female diamondback moths in area-wide integrated pest management programs that have a sterile insect technique (SIT) component.