Activity of Bacillus thuringiensis isolates on Lasioderma serricorne (F.) (Coleoptera: Anobiidae)

Abstract

Three Bacillus thuringiensis (Bt) strains isolated from stored tobacco residues were characterized and tested for their insecticidal activity against larvae of the cigarette beetle, Lasioderma serricorne (F.) (Coleoptera: Anobiidae). The molecular genetic analysis of the three isolates showed high homology to B. thuringiensis subsp. tenebrionis. The 65 kDa crystal toxin present in all the strains was found to be encoded by genes identical to the cryIIIA gene responsible for the insecticidal activity of B. thuringiensis subsp. tenebrionis. Diet incorporation bioassays were used to compare the activity of the tobacco Bt isolates with that of the anticoleopteran B. thuringiensis subsp. tenebrionis and two commercially available bioinsecticides. The responses to spore/crystal suspensions from all strains were in the range of 60–80% mortality after 7 days. The purified parasporal crystals showed a slightly lower insecticidal activity. The effects of exposure to sublethal doses on larval development and adult emergence were estimated.