The clove essential oil was diluted to three different concentrations (1.20, 2.40, and 4.80 mg oil/ml) with tap water after being dissolved in detergent (1:1 v:v; as a surfactant, purchased from Beijing goldfish technology Co., LTD, Beijing, China). The same concentrations of detergent alone served as a negative control, and tap water was used as a blank control. The solutions were applied (about 1.5 liters per tree) in a completely randomized block design by atomizer (purchased from Alibaba, China) and the trees in one plot constituted a single treatment.