The in vitro efficacy of a Zimbabwean isolate of Zoophthora radicans Brefeld (Batko) in the control of Lepidoptera larvae infesting Brassica sp.

Abstract

The use of microbes in pest control is an important aspect of integrated pest management (IPM). A Zimbabwean isolate of the fungal entomopathogen Zoophthora radicans was tested for efficacy in the control of Brassica infesting lepidopteran larvae. Z. radicanscaused 98.68% mortality on small (1st - 2nd instar) diamondback moth (Plutella xylostellaL.) larvae and 21.34% mortality on large (3rd - 4th instar) diamondback moth (DBM) larvae 6 days after treatment. Z. radicans was not effective against larvae of Helicoverpaarmigera, webworm (Hellula undalis), cabbage moth (Crocidolomia sp.) and cabbage looper (Trichoplusia ni). There was no significant difference (p > 0.05) in adult Cotesia plutellae emergence from cocoons treated with Z. radicans and cocoons sprayed with water. There was 95% emergence of C. plutellae adults from cocoons treated with Dimethoate 40 EC. No adults of C. plutellae emerged from cocoons treated with Carbaryl 75 WP, Malathion 25 WP and Malathion 50 EC. The study showed that Z. radicans was effective against early instar DBM larvae and did not have adverse impacts on the emergence of C. plutellae adults from cocoons and Diaeretiella rapae adults from aphid mummies. Key words: Zimbabwe, Zoophthora radicans, efficacy, in vitro, Lepidoptera, Brassica spp.