Effectiveness of Bacillus thuringiensis strains against Spodoptera frugiperda (Lepidoptera: Noctuidae)

Abstract

The fall armyworm (Spodoptera frugiperda) is one of the most important pests of maize, causing up to 20% production losses when defoliation occurs near to flowering, or even complete destruction of plants. Among the alternatives to control this pest, the use of Bacillus thuringiensis (Bt) has gained attention due to its efficiency and low impact on natural enemies. Strains Bt dendrolimus HD 37, Bt aizawai HD 68, Bt kurstaki HD 73, Bt darmstadiensis HD 146, and Bt thuringiensis 4412 were tested against second instar larvae in in vivo assays. Suspensions of Bt aizawai HD 68 and Bt thuringiensis 4412, containing 3 x 108 cells/ml, induced mortality of 100% and 80.4%, respectively. To test virulence, cell concentrations of 8 x 105 to 3 x 108 cells/ml of strains Bt aizawai HD 68 and Bt thuringiensis 4412 were applied on the second instar larvae: LC50 were 6.7 x 106 and 8.6 x 106 cells/ml, respectively.