Potential of standard strains of Bacillus thuringiensis against the tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

BackgroundThe tomato pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the key pests of tomato worldwide, causing an estimated crop loss of 80 to 100%. This pest has developed resistance to several pesticides due to overuse, resulting in control failures in the field. The use of biological insecticides as Bacillus thuringiensis that expressed insecticidal proteins can be an alternative tool by insecticides to suppress the pest population.Main bodyLaboratory study investigated the efficacy of standard Bacillus thuringiensis (Bt) strains (4D1, 4D4, 4G1, 4K5 and 4XX4) against T. absoluta. Bioassay was conducted using tomato leaf discs treated with spore crystal lysates prepared from the standard strains, and mortality data was subjected to concentration-mortality probit analysis. The LC50 values for Bt 4D1, Bt 4D4 and Bt 4G1 were 6.10, 6.62 and 8.18 mu g/ml for the 2nd instar; 9.90, 10.20 and 11.12 mu g/ml for the 3rd instar; and 19.82, 23.16 and 24.54 mu g/ml for the 4th instar, respectively, while the Bt 4K5 and Bt 4XX4 were not toxic to T. absoluta.ConclusionThis study suggests that Bt strain 4D1 is effective against different larval instars of the pest and can be used in its management.