Crude Bacillus thuringiensis pellets efficiently combats Eutetranychus orientalis,the spider mite

This study demonstrates the efficacy of the crude pellet of Bacillus thuringiensis subs. kurstaki (Btk) obtained by SmF or SSF to combat Eutetranychus orientalis Klein. For bioassay, the mites were collected from infested leaves of Vigna unguiculata and Moringa oleifera, and reared by leaf-disc method employing artificial feeding system. In terms of LC₅₀ values, the crude Btk-toxin (probit: 9.51 mg/mL) obtained by SSF was 2.2-fold more efficient in killing E. orientalis than that of SmF (probit: 22 mg/mL). For the efficacy trial with potted plants, 10 mg crude Btk-toxin obtained by SSF was directly sprayed on the infested plants (V. unguiculata), which completely eliminated the mites from the infested plants within 12 days of treatment. In comparison, the survival rate of mites which received Btk-toxin from SSF was significantly (P < 0.0001) lesser than those received Btk-toxin from SmF. In this first report, apart from the efficiency of Btk-toxin in solid-fermented matter to deter the mites without supplementing any adhesive or surfactant in the diet, a feeding system for its rearing in the laboratory coupled with bioassay was also demonstrated.