Effect of <em>Bacillus thuringiensis </em>Berliner new strains against <em>Plutella xylostella</em> (Linnaeus, 1758) (Lepidoptera: Plutellidae)

Abstract

Viewing to study the pathogenicity of Bacillus thuringiensis strains on biological characteristics of P. xylostella, bioassays were made in which 58 strains of B. thuringiensis, a positive control with the strains HD1 from B. thuringiensis var. kurstaki, a negative control with B. thuringiensis var. tenebrionis (Coleopteran specific) were evaluated. Water with an adhesive spreader (Tween20^®) was used as a standard check. Bacterial suspensions were sprayed on leaf disks of kale and later supplied to 2^nd instar caterpillars of P. xylostella for food consumption in confined condition using disposable Petri dishes. Total mortality of caterpillars was observed in 11 of the evaluated strains and the remainder affected negatively pest biological lifecycle, being classified in groups A (A1, A2 e A3) and B (B1 e B2), respectively, in relation to the most harmful action over main biological characteristics of P. xylostella. Larve, pupae mortality and period of the larve period were more relevants parameters to determine which isolates affected most P. xylostella biology. It was thus verified that the isolates T3A.140, T3A.259, T08.024, E1, E26, 2.7L, 1.7L, E22, and 22.7L, caused 100 % larval mortality and are so thought to have the highest potential for development as commercial bioinseticides. The strains which were classified in group A could be also used in integrated pest management programs of P. xylostella, in Brassicaceae crops.

Additional Keywords: diamondback moth; entomopatogenous; brassica; resistance.