Releases of Trichogramma minutum1 and T. cacoeciae1 in an Apple Orchard and the Effects on Populations of Codling Moths 2

Continuous releases of a local strain of Trichogramma minutum Riley (in 1966, 1967, 1968) and of T. cacoeciae Marchal (in 1968) were made in portions of an apple orchard during the period when adult codling moths, Laspeyresia pomonella (L.), were present. In 1966, at harvest, fruit from the treated trees contained 27–34 larvae per 100 fruit; fruit from untreated trees contained 102–122 per 100 fruit. In 1967, 15.0% of the apples in the release area were injured at harvest compared with slightly less than 19.4% in the untreated check. In 1968, although the eggs of the codling moth and of the redbanded leafroller, Argyrotaenia velutinana (Walker), introduced into the release trees were 46–75% parasitized, 83.2–92.8% of the apples on the treated trees were infested or damaged at harvest.