INTERACTIONS AMONG HELICOVERPA-ARMIGERA (LEPIDOPTERA, NOCTUIDAE), ITSLARVAL ENDOPARASITOID MICROPLITIS-CROCEIPES (HYMENOPTERA, BRACONIDAE), AND BACILLUS-THURINGIENSIS

Interactions among Helicoverpa armigera (Hubner), its larval endoparas itoid Microplitis croceipes (Cresson), and Bacillus thuringiensis Berl iner were evaluated under laboratory conditions. Prefeeding H. armiger a with lethal concentrations (0.08 and 0.16 mg/g) of Dipel (B. thuring iensis subsp, kurstaki strain HD-1) did not prevent M. croceipes from ovipositing in the infected host larvae. Development of parasitoid imm atures in host larvae prefed for 24 or 48 h with the dietary B. thurin giensis was not adversely affected. However, feeding on the same diets for 72 h was detrimental to the parasitoid because of premature host mortality. Continuous exposure of H. armigera larvae to the diets at d ifferent time intervals after parasitization (0, 4, or 6 d), prevented successful development and pupation of M. croceipes, mainly caused by early mortality of the host. Feeding parasitoid adults with B. thurin giensis preparations of subsp. kurstaki strain HD-73 mixed in honey wa s not harmful to the wasps. Moreover, Dipel or purified B. thuringiens is spores of HD-73, but not purified crystals of this strain, increase d longevity of the wasps compared with the control (honey alone). Micr oscopic observations and color indications showed that the adult paras itoid ingested the honey with the Dipel. The incompatibilities between application of B. thuringiensis to host larvae and parasitization wit h M. croceipes are discussed with regard to combining microbial and en tomophagous control strategies against H. armigera.