Response of the melon fly parasitoidPysttalia fletcheri (Hymenoptera: Braconidae) to host-habitat stimuli

Abstract

Cohorts of mass-reared adult female Pysttalia fletcheri, parasitoids of the melon fly (Bactrocera cucurbitae), were exposed to host-plant stimuli in a laminar airflow wind tunnel to analyze the cues used in host-habitat finding. Parasitoids hovered twice as frequently around plastic zucchini models emitting fresh cucumber odor as around models emitting clean air. The odor of decaying pumpkin was even more attractive, resulting in over a 10-fold increase in hovering, a 50-fold increase in landing, and a 150-fold increase in host-searching and probing behaviors compared to clean air. Fresh cucumber leaf odors were not attractive to the parasitoids, but decomposing leaves elicited a strong increase in hovering, landing, and searching behaviors. Plastic leaves which visually simulated cucurbit foliage did not in themselves significantly alter orientation behaviors, but the combination of leaf visual stimuli plus decaying leaf odors caused strong increases in hovering, landing, and searching. Fresh pumpkin odor and the odor of yeast-inoculated pumpkin were not as attractive to parasitoids as decaying leaf odors. Yeast isolated from decaying pumpkin and cultured on various sterile media were not substantially more attractive than clean air.