Baseline susceptibility of red flour beetle (Tribolium castaneum Herbst) to Bacillus thuringiensis toxins

In search of environmentally safe method for controlling the red flour beetle, Bacillus thuringiensis toxins from a variety of isolates were evaluated. Dung and soil samples were found to be rich sources for potentially useful B. thuringiensis strains. Isolates were first confirmed through morphological and biochemical characteristics. Selected isolates showed variability in their toxicity when checked against selected insect pests. Pesticidal activity of purified B. thuringiensis proteins mixed at different concentrations with artificial diet yielded 70% to 80% mortality in second instar larvae of selected insect pests. The B. thuringiensis strain isolated from bird droppings was found to be the best potential source of toxin and had the lowest LC50, whereas the highest LC50 was recorded in a sample of isolate obtained from cow dung.