The effects of Thuricide “HP” (a biological insecticide, whose active
ingredient is based on Bacillus ihuringiensi var. kurstaki Berliner) for the
control of S. littoralis larvae were evaluated in laboratory tests. Larvae of the
early three instars were more susceptible than those of the elder ones. thus
indicating that successful control of the cotton leafworm may be obtained if B.
thuringiensis application was oriented against the early larval instars. Treatment
of fourth instar larval caused high mortality percentage amongst the resulting
pupae. while the lowest percentages of the obtained adults resulted from larvae
of all 4 instars treated with 15x106 spores/g. Pupal and adult deformations
increased after the 2iiçj. and 41ji instar larval treatment among all concentrations.
Adult longevity was not affected due to larval treatment, but reduced fecundity
females of was observed. The obtained eggs hatched normal Spores of B.
thuringiensis were detected in the abdomens of adults that resulted after larval
feeding on contaminated castor-bean leaves.