Vol. 9, Issue 8, Part B (2025)

A bioassay was undertaken to evaluate the impact of pesticide-treated mulberry leaves on the larval parameters of silkworm hybrid FC2. The pesticides used for efficacy study against mulberry pests were selected based on recommended label doses and sprayed onto the plants. Leaves were harvested and fed to silkworms at intervals of 5, 10, 15 and 20 days after spraying (DAS) to assess their residual toxicity. The study revealed that Azadirachtin 1% (2 mL/L) and Chlorfenapyr 10 SC (1.5 mL/L) exhibited the highest levels of toxicity with larval mortality rates of 100% and 24.75%, respectively at 10 DAS. Toxicity from both chemicals declined significantly at 15 DAS. In contrast, Orgomite, a botanical pesticide (2.5 mL/L), demonstrated minimal toxicity causing only 7.50% mortality at 10 DAS. Wettable Sulphur 80 WP (2 g/L) and Era Safeguard (2.5 mL/L) were also relatively safer with mortality rates of 8.58% and 18.50%, respectively at the same interval. Additionally, the longest fifth instar larval duration was observed in the Chlorfenapyr treated group while the shortest was seen in the water sprayed control and Orgomite treated groups. Corresponding reductions in larval weight and effective rate of rearing were observed in accordance with toxicity levels. The findings indicate that Orgomite was the safest among the tested products, followed by Wettable Sulphur and Era Safeguard even within 10 days of application. Chlorfenapyr 10 SC, while effective required a minimum safety interval of 15 days to minimize harm to silkworms. Therefore, Orgomite and Chlorfenapyr 10 SC can be recommended for effective pest management in mulberry with respective post-spray safety periods of 10 and 15 days for safe silkworm rearing.