Parasitism of diamondback moth by Oomyzus sokolowskii

Abstract

The objective of this work was to evaluate the parasitism capacity of the larval-pupal parasitoid Oomyzus sokolowskii submitted to different densities of the host diamondback moth, Plutella xylostella, in the laboratory, greenhouse and field. In the laboratory and in the field, O. sokolowskii was exposed to densities of 2, 4, 8 or 16 larvae. In the laboratory, 300 mL recipient were used, and in the field kale plants were placed in cages (30x50 cm). In the greenhouse, microparcels consisted of six cabbage plants each infested with 25, 50, 85 or 100 larvae. The number of parasitized larvae increased with host density and varied from 1.7 to 10.4 (laboratory) and from 0.61 to 7.0 (field). In the greenhouse, parasitism rate was higher in microparcels with higher host infestation. The time of exposition was significant, with higher parasitism rate at 72 hours after host exposure (24 hour, 52.4%; and 72 hour, 80.7%), irrespective of host density. Oomyzus sokolowskii responds to increases in host density, but maintains the parasitism rate unchanged irrespective of variations in the host availability.