Virion-free plasma from entomopoxvirus-infected larvae of Pseudaletia separata (Lepidoptera : Noctuidae) kills larvae of a braconid endoparasitoid, Cotesia kariyai (Hymenoptera : Braconidae) cultured in vitro

Virion-free plasma from larvae of the armyworm, Pseudaletia separata, infec ted with an entomopoxvirus (PsEPV), adversely affects the embryonic and lar val stages of the gregarious braconid endoparasitoid, Cotesia kariyai. We i nvestigated the toxicity of virion-free plasma from PsEPV-infected P. separ ata larvae against C. kariyai embryos and larvae cultured in vitro. Parasit oid larvae collected from host larvae were individually transferred into pl astic Petri dishes with IPL-41 medium and cultured at 25 degrees C for 7 d. The development of C. kariyai larvae was adversely affected when virion-fr ee plasma was added to IPL-41 medium, even up to a dilution of 128. The mor tality of in vitro-cultured parasitoid larvae decreased with increases in t he concentration of virion-free plasma added to the medium. The parasitoid larvae became less susceptible to the lethal factor as the larval stage inc reased. Parasitoid larvae cultured in IPL-41 medium added to virion-free pl asma developed little if at all, and shrank and died 2 to 6 d after the sta rt of culture, regardless of the larval stage of the parasitoid. In dead pa rasitoid larvae, the tissue receded from the cuticle and organs lost their organization and cellular integrity. Embryos cultured in IPL-41 medium cont aining virion-free plasma never progressed beyond the egg stage, and somati c tissues lost their organization. On the other hand, embryos cultured in I PL-41 medium containing normal plasma developed to the first stadium.