Effect of pesticide application techniques on thrips control in the cowpea flowering stage

Thrips are among the most damaging pests to cowpeas in Hainan, China. Conventional pesticide application methods often fail to achieve satisfactory control due to the small size and concealed habitats of thrips. This study aimed to enhance the efficacy of pesticides by improving their application techniques. The optimal application time of day was identified, and the physicochemical properties of four types of spray adjuvants were tested to evaluate their impact on efficacy. A terrestrially targeted air-assisted sprayer for cowpeas was designed to adjust the wind direction and target at thrips hiding spots. Field trials were conducted in Hainan to assess the efficacy of modified application times, adjuvant addition, and targeted air-assisted spraying.

The results indicate that clear weather and an 8:00 a.m. application time are optimal, with a 22.52% and 30.22% increase in efficacy compared to applications at 10:00 a.m. and 4:00 p.m., respectively. Two adjuvants, Qigong and Beibeijia, were selected and, when used with a knapsack sprayer, increased efficacy by 28.50% and 17.92%, respectively. The terrestrially targeted air-assisted sprayer significantly improved the reduction rate of the thrips population by 27.31% and 21.77% compared to knapsack sprayers and spray guns, respectively.

The use of the cowpea terrestrial air-assisted sprayer with adjuvants at 8:00 a.m., compared to the conventional application method by farmers using electric knapsack sprayers, resulted in at least a 40.03%, 46.08%, and 52.22% increase in efficacy at 1, 2, and 3 days after treatment, respectively. The findings provide a scientific basis for efficient thrips control in cowpeas. © 2024 Society of Chemical Industry.