Abstract: In order to promote the effective utilization of pesticides in cotton fields, field tests were conducted during 2011-2012 to determine the appropriate spray method and volume used to control the cotton aphid, Aphis gossypii (Glover). Deposition of insecticides applied with the lever-operated knapsack sprayer and the knapsack mist blower at different spray volumes in cotton fields were studied by adding tracer allura red in insecticide solution. The results indicated that at the seedling stage of cotton, when 3% acetamiprid EC was applied with the mist blower at the dose of 450 mL/ha, the run-off rates were 24.4%, 28.9% and 26.7% at the spray volumes of 75, 150 and 225 L/ha, respectively. The runoff rates of 3% acetamiprid EC from the lever-operated sprayer operated at the the spray volumes of 300, 450 and 600 L/ha were 35.6%, 37.8% and 46.7%, respectively. Efficacy of acetamiprid applied with two sprayers at different water volumes against cotton aphids had no significant difference (P>0.05). At the adult-plant stage of contton, when 25% pymetrozine WP was applied at the dose of 300 g/ha, the run-off rates of pymetrozine for the lever-operated sprayer at the the spray volume of 600 L/ha and the mist blower at the the spray volume of 150 L/ha were 13.3% and 3.3%, respectively. The efficacy of pymetrozine applied at the dose of 225 g/ha using the mist blower at the the spray volumes of 150 and 300 L/ha had no significant difference compared with the treatment of 300 g/ha pymetrozine applied with the lever-operated sprayer at the spray volume of 600 L/ha (P>0.05). It is so concluded that low volume spray with the mist blower could facilitate not only to reduce the insecticide dosage used in cotton fields for aphid management, but also to decrease the run-off rate of insecticide onto soil and so reduce environmental pollution.

Key words: Aphis gossypii, pymetrozine, spray method, spray volume, pesticide deposition, control efficacy