Optimizing λ-cyhalothrin for the effective control of Alphitobius diaperinus: Temperature and food effect revealed

The lesser mealworm, Alphitobius diaperinus, presents substantial challenges as a secondary pest in global stored-product management, especially within the poultry industry. This study examines the effectiveness of λ-cyhalothrin, a synthetic pyrethroid, against A. diaperinus larvae and adults under various abiotic and biotic conditions. Bioassays were conducted at both half-label and label doses across different post-exposure temperatures ranging from 20 to 35 °C. The results demonstrate that λ-cyhalothrin exhibits temperature-dependent efficacy within a 7-day exposure period, with higher temperatures resulting in increased mortality rates for both tested life stages. For larvae, mortalities ranged 81.1 (20 °C)–94.4% (35 °C) (half-label dose in the absence of food), 90.0 (20 °C)–100.0% (35 °C) (label dose in the absence of food), 72.2 (20 °C)–85.6% (35 °C) (half-label in the presence of food), 88.9 (20 °C)–100.0% (35 °C) (label dose in the presence of food) 7 days post-exposure. For adults, mortalities ranged 35.6 (20 °C)–74.4% (35 °C) (half-label dose in the absence of food), 43.3 (20 °C)–97.8% (35 °C) (label dose in the absence of food), 24.4 (20 °C)–65.6% (35 °C) (half-label in the presence of food), 38.9 (20 °C)–94.4% (35 °C) (label dose in the presence of food) after 7 days of exposure. Additionally, the significance of food substrate presence in absorbing and providing a barrier against insecticidal toxicity is highlighted, as it negatively impacted mortality rates. Overall, these findings elucidate the complex interactions among temperature, dosage, and environmental factors that optimize λ-cyhalothrin administration efficiently managing A. diaperinus.