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 Hubner, 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 the y persisted in release fields, and what minimum number of release points pe r unit area would be adequate to ensure uniform distribution of the wasps f or augmentative releases. Dispersal was monitored from central release poin ts over distances from 35 to 230 m, in a square 9 ha grid of monitoring poi nts, using yellow sticky cards and O. nubilalis sentinel egg masses to dete ct 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 s ticky cards and sentinel egg mass parasitism decreased with distance from p oint of release, although 11-40% parasitism of egg masses occurred in monit oring positions most distant from the release points. Uniform parasitism of sentinel egg masses was achieved in areas of 1-2 ha surrounding central re lease points. It is suggested that a single release point per hectare shoul d be adequate to ensure uniform dispersal of T. ostriniae into sweet corn f ields. (C) 2001 Academic Press.