Evaluating the Compatibility of Spinosad and Alpha-Cypermethrin for Controlling Six Insect Pests Infesting Stored Wheat

SIMPLE SUMMARY: This study investigated the effectiveness of combining spinosad and alpha-cypermethrin against major wheat storage pests, including Rhyzopertha dominica, Tribolium castaneum, Cryptolestes ferrugineus, Sitophilus oryzae, Oryzaephilus surinamensis, and Trogoderma granarium. Spinosad was tested at two concentrations and alpha-cypermethrin was used at one concentration in laboratory conditions. The results show that combining both treatments led to higher pest mortality compared to individual treatments. The most effective treatment combination was the application of the high dose of spinosad with alpha-cypermethrin, resulting in the highest mortality and substantial progeny reduction. Trogoderma granarium was found to be the most tolerant pest, followed by O. surinamensis, C. ferrugineus, T. castaneum, S. oryzae, and R. dominica. This study suggests that combining alpha-cypermethrin and spinosad can be an effective strategy for protecting stored wheat against multiple insect pests. ABSTRACT: The deterioration of stored wheat due to pest infestations is a significant concern, with pests like Rhyzopertha dominica, Tribolium castaneum, Cryptolestes ferrugineus, Sitophilus oryzae, Oryzaephilus surinamensis, and Trogoderma granarium being major contributors. This study examined the efficacy of spinosad and alpha-cypermethrin, individually and in combination, against these pests under laboratory conditions. Spinosad was tested at two concentrations (0.05 and 0.1 mg/kg), while alpha-cypermethrin was applied at 0.05 mg/kg. The combined application of both insecticides led to significantly higher pest mortality compared to single treatments. Importantly, all treatments caused substantial pest mortality and exhibited the ability to suppress pest progeny production over time, as observed in both laboratory and persistence trials. Among the various treatment combinations, the joint application of 0.1 mg/kg spinosad and 0.05 mg/kg alpha-cypermethrin emerged as the most effective, resulting in elevated mortality and a marked reduction in pest progeny. Rhyzopertha dominica exhibited the highest susceptibility among the pests, followed by S. oryzae, T. castaneum, C. ferrugineus, O. surinamensis, and T. granarium. The remarkable performance of the joint action of alpha-cypermethrin and spinosad at low doses highlights this combination as an efficacious approach for safeguarding stored grain against these destructive insect pests, warranting further exploration.