Study of Dispersal as a Selection Criterion for Trichogrammatidae for Biological Control in Cauliflower Greenhouses

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is the most important pest of cultivated Brassica species worldwide, including several greenhouse crops, such as cauliflower seed crops. With the aim of selecting a candidate strain from the Trichogrammatidae (Hymenoptera: Chalcidoidea) for the control of diamondback moth in cauliflower greenhouses, we assessed the dispersal capacity of eight trichogrammatid strains, using sticky traps in a greenhouse cauliflower crop with a simplified structure. We determined the percentage of females trapped at various distances from the release point on various numbers of days after release. The results obtained were compared with the theoretical trapping probability. A dispersal index, weighted mean distance, was also calculated. Trichogramma chilonis Ishii from Reunion Island and T. ostriniae Pang & Chen from Japan dispersed most rapidly and over the greatest distances. The five best strains (T. chilonis from Japan and Reunion Island, T. evanescens Westwood from Egypt, T. ostriniae from Japan and T. semblidis Aurivillius from France) were then tested in realistic conditions of a cauliflower seed crop grown in a greenhouse. In both the studies carried out, T. chilonis from Reunion Island gave the highest percentage of females trapped and trichogrammatid dispersal capacity decreased with increasing crop density. These findings have implications for integrated pest management in cauliflower seed crops grown in the greenhouse.