Dispersal and parasitism of Heliothis virescens eggs by Trichogramma pretiosum (Riley) in cotton

This study was carried out in cotton fields in Lambayeque, Peru to investigate dispersal and parasitism by Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae), an egg parasitoid of Heliothis virescens (Fab.) (Lepidoptera: Noctuidae). Experiments were conducted in a cotton crop 38 to 55 days old, in plots of 625 m(2). The release of T. pretiosum adults was done at two densities: 160 000 and 320 000 parasitoids/ha. Two release strategies were used: (1) one day prior to adult emergence (pupae), and (2) adults one day post-emergence and fed on honey. Parasitoids released as pupae achieved low parasitism. Parasitism resulting from release of adults was higher than that resulting from Trichogramma spp. present in the crop prior to parasitoid release. There was no difference between parasitism upwind and downwind of the release point at points along a transect for 10 m, except in the case of pupae released at a density of 160 000 parasitoids/ha which showed lower upwind parasitism. Parasitism of eggs found on developed leaves was higher than that on terminal buds.