Entomopathogenic screening of native Bacillus thuringiensis (Berliner) isolates against Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) under laboratory condition

Abstract

Fall Armyworm, Spodoptera frugiperda (J E Smith) (Lepidoptera, Noctuidae) is native to the tropical and subtropical region of America. Being a polyphagous pest known to cause major damage to economically important cultivated grasses. This insect is one of the most important pests of maize, being firstly registered in the India in 2018 and it causes a 33% yield loss in the plant production. The use of chemical pesticides as a prophylactic method causes some problems such as ecological instability, pollution, high costs and death of natural enemies. In the current study, screening of native B. thuringiensis isolates and their insecticidal activities were tested against the 2nd instar larvae of maize fall armyworm, Spodoptera frugiperda under laboratory condition. Preliminary bioassay was conducted using diet incorporation method and treated with spore crystal lysates prepared from the native Bacillus thuringiensis isolates. Upon screening 50.0 per cent (of the B. thuringiensis isolates exhibited mortality in the range of 26-50 per cent while 10.0 per cent of the B. thuringiensis isolates showed more than 75 per cent mortality after 7 days of exposure. Among the seventy isolates, Bt-Oa1 and Bt-257 recorded maximum of 86.84% mortality after 7 days after treatment.