Dispersal Behavior of Trichogramma ostriniae (Hymenoptera: Trichogrammatidae) in Sweet Corn Fields: Implications for Augmentative Releases against Ostrinia nubilalis (Lepidoptera: Crambidae)

The dispersal behavior of Trichogramma ostriniae Pang et Chen, a potential biological control agent of European corn borer, Ostrinia nubilalis Hübner, was investigated in fields of sweet corn in central New York. The aims of the study were to quantify T. ostriniae dispersal, to determine whether they persisted in release fields, and what minimum number of release points per unit area would be adequate to ensure uniform distribution of the wasps for augmentative releases. Dispersal was monitored from central release points over distances from 35 to 230 m, in a square 9 ha grid of monitoring points, using yellow sticky cards and O. nubilalis sentinel egg masses to detect T. ostriniae. Results showed that the wasps dispersed rapidly, up to 180 m in 6 days and 230 m in 21 days. The number of T. ostriniae captured on sticky cards and sentinel egg mass parasitism decreased with distance from point of release, although 11–40% parasitism of egg masses occurred in monitoring positions most distant from the release points. Uniform parasitism of sentinel egg masses was achieved in areas of 1–2 ha surrounding central release points. It is suggested that a single release point per hectare should be adequate to ensure uniform dispersal of T. ostriniae into sweet corn fields.