Effects of Application Method, Spray Volume, and Insecticide Mobility on the Control of Stephanitis chinensis

Emerging or poorly studied pests may require control before detailed information is available on their biology or management. We used Stephanitis chinensis Drake (Hemiptera: Tingidae), a poorly studied tea pest that feeds mainly on abaxial leaf surfaces, to determine how insecticide mobility, application method, and spray volume affect control efficacy. Twelve insecticides assigned to literature-based plant-mobile or contact-dominant categories were tested in leaf-dip bioassays at recommended field-rate concentrations and in field trials comparing misting with conventional spraying at 450 and 900 L/ha. Water-sensitive paper measured abaxial deposition across three canopy levels. At 48 h, 11 insecticides caused 90.0–100.0% mortality, whereas rotenone caused 66.0%. Field efficacy was significantly affected by mobility, application method, and assessment day, but spray volume had no significant main effect. Misting significantly improved efficacy in 34 of 36 comparisons for contact-dominant insecticides and 11 of 36 for plant-mobile insecticides; increasing spray volume improved only 1 of 72 comparisons. Under misting, droplet density and coverage exceeded measurement limits throughout the canopy (>300 droplets/cm2); conventional spraying produced lower deposition that declined toward the lower canopy. Improving abaxial and within-canopy deposition was more effective than increasing spray volume. Misting improved efficacy more frequently for contact-dominant insecticides such as bifenthrin and pyrethrins, whereas plant mobility of thiamethoxam, imidacloprid, sulfoxaflor, cyantraniliprole, and matrine may partly compensate for inadequate deposition.