Evaluation of the Efficacy of Some Chemical and Biological Pesticides in Controlling the Two-spotted Spider Mite (Tetranychus urticae) on Different Common Bean (Phaseolus vulgaris) Cultivars and their Impact on Pest Population Dynamics

The two-spotted spider mite, Tetranychus urticae Koch, is a major pest damaging common bean crops worldwide. This study was conducted to monitor the population dynamics of T. urticae on four common bean cultivars (Bronko, Giza-6, Valentino, and Nebraska) during 2023 and 2024 growing seasons. Also, the efficacies of six acaricides, against the motile stages of the mite, were assessed. Results showed significant differences in cultivar susceptibility. Nebraska exhibited the highest infestation levels, while Bronko demonstrated the greatest tolerance, likely due to morphological and biochemical defense mechanisms. Valentino and Giza-6 showed intermediate susceptibility. Seasonal variations influenced population peaks, with earlier infestations observed in 2024, potentially due to climatic factors. Acaricide efficacy trials revealed that abamectin was the most effective, followed by spiromesifen and fenpyroximate. Bifenazate provided moderate control, while pyridaben and hexythiazox were the least effective, likely due to insect tolerance and to mode of action of acaricides. These findings emphasize the need for integrated pest management strategies, including the selection of insect-tolerant cultivars and acaricide rotation to mitigate resistance. Continuous monitoring of insect populations is recommended to improve control measures. The present study can be recommended to carry out further studies for the management of the two-spotted spider mite, T. urticae on common bean.