Observations on the effect of regular releases of Trichogramma spp. in controlling Heliothis spp. and other insects in cotton

Abstract

Regular releases of the egg parasite Trichogramma sp. (from Western Australia) were made at the rate of 50000 adults/ha from November 1975 to March 1976 on 8 ha of cotton in south-eastern Queensland. Whole-plant sampling indicated the presence of adult parasites in the crop, but the observed mean rate of egg parasitism (49.4%) was insufficient to provide adequate control of Heliothis spp. Some control of larvae of Heliothis was provided by populations of predators (including the spider Cheiracanthium mordax L. Koch (diversum L. Koch) and the carabid Calosoma schayeri Erichs.) that built up in the trial site. A single spray application of Bacillus thuringiensis and chlordimeform (chlorphenamidine) at 350 g/ha provided adequate control of a larval population of Anomis flava (F.) that built up in the unsprayed crop. This treatment did not affect the emergence of adult parasites from the host eggs (Sitotroga cerealella (Ol.)) that were used to distribute the parasite. Eggs of A. flava were not parasitised by Trichogramma. Crocidosema plebejana Zell. was active throughout the season and caused some damage to the crop.