BENZOYLPHENYL UREAS EFFECT ON GROWTH AND DEVELOPMENT OF EULOPHUS-PENNICORNIS (HYMENOPTERA, EULOPHIDAE), A LARVAL ECTOPARASITE OF THE CABBAGE MOTH (LEPIDOPTERA, NOCTUIDAE)

The hymenopteran parasitic wasp, Eulophus pennicornis, shows promise for controlling Mamestra brassicae. The effect of the benzoylphenyl ureas diflubenzuron, hexaflumuron, and teflubenzuron was examined by feeding treated cabbage leaves to host caterpillars, by topical application, or by spraying the caterpillars. Development of the parasitic wasp on caterpillars treated with benzoylphenyl ureas was affected in a concentration-dependent manner. The highest effect occurred in the early larval stadia. After feeding treated cabbage leaves to caterpillars, hexaflumuron was the most toxic compound followed by teflubenzuron and diflubenzuron. The lowest concentration (0.05 mu g [AI] per caterpillar) of hexaflumuron teflubenzuron: and diflubenzuron, applied topically to a M. brassicae caterpillar resulted in 10, 45, and 59%, respectively, normal E. pennicornis adults. Spraying diflubenzuron at a concentration of 6.4 mg (AI)/liter on the host caterpillar caused 30% mortality in E. pennicornis larvae compared with 94% for teflubenzuron and 99% for hexaflumuron al a concentration of 3.4 and 12.7 mg (AI)/liter, respectively. Female parasites did not suffer significant mortality by contact with the chemicals, but there was up to 70% reduction of progeny formation at a concentration of 38.1 mg (AI)/liter for hexaflumuron or 10.2 mg (AI)/liter for teflubenzuron. These results indicated that the use of chitin synthesis inhibitors at recommended doses may inhibit the development of the parasite.