Evaluation of Co-toxicity Coefficient for Combined Impact of Botanicals with Spinosad against Pulse Beetle, Callosobruchus maculatus in stored Blackgram

Background: Blackgram is an important pulse crop in India, but storage pests such as Callosobruchus maculatus can cause severe damage. Synthetic insecticides are commonly used to manage these pests, but mixing them with food grains is not recommended. Instead, safer alternatives like botanicals can be used. However, botanical powders have a short post-application duration, which reduces their effectiveness. To enhance their efficacy, spinosad can be combined with botanical powders, resulting in a cost-effective and long-lasting solution. This study aims to evaluate the toxicity of this combination against C. maculatus. Methods: Botanicals like sweet flag powder and neem kernel powder were used in the experiment. Spinosad was mixed with these treatments and was used for the bio-assay with one-day-old adults of C. maculatus by mixing with blackgram seed. Mortality data were recorded at 1,2,3,5 and 7 days after the release of the test insect to calculate LD50 and other parameters for botanicals in combination with spinosad. Result: The highest co-toxicity coefficient was recorded for sweet flag powder (141.17) than neem kernel powder. Compared to neem kernel powder, sweet flag powder enhanced the mortality rate when combined with spinosad. Hence, a combination of sweet flag powder and spinosad is recommended for the control of C. maculatus.