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

Polanczyk, Ricardo AntônioSilva, Rogério Fernando Pires daFiúza, Lídia Mariana

The fall armyworm ("Spodoptera frugiperda") is one of the most important pests of maize, causing up to 20(per cent) 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 10 8 cells/ml, induced mortality of 100(per cent) and 80.4(per cent), respectively. To test virulence, cell concentrations of 8x10(5) to 3x10(8) cells/ml of strains "Bt aizawai" HD 68 and "Bt thuringiensis" 4412 were applied on the second instar larvae: LC(50) were 6.7x10(6) and 8.6x10(6) cells/ml, respectively.