Efficacy of a cold fogger sprayer for control of orchid midge

Abstract

Study on efficacy of a cold fogger sprayer for controlling orchid midge, Contarinia maculipennis Felt in orchid nurseries at Nakornpathom province during October 2015 to September 2017 were investigated. Field study by colorimetric method was performed to compare the spray deposition and spray run-off under actual working conditions. RCB design was planed with 6 treatments and 4 replicates. Very low volume treatments were applied with the cold fogger sprayer at 6, 8, 10 and 12 l/rai with 3.0 meter swath width. High volume treatments were applied with a spray lance length of 0.4 meter with adjustable cone nozzle connected to high pressure pump sprayer. Rates of application were 120 (recommendation rate) and 160 l/rai (farmer use rate) with 0.5 meter swath width. The results indicated that the spray deposition on orchid spike provided by the cold fogger sprayer was not different when compared with the high pressure pump sprayer method. In addition, the cold fogger sprayer could effectively reduce spray run-off by more than 13 times as compared with the high pressure pump sprayer. Subsequently, two field studies were performed to evaluate the bio-efficacy of spraying techniques, both very low and high volume with the application of Thiamethoxam/lambda-cyhalothrin (24.7% ZC) at 120 and 160 ml/rai. It was found that the control of orchid midge of all treatments were equally effective. The cold fogger sprayer reduced the use of insecticide by 25%, as compared with farmer method. Furthermore, the cold fogger sprayer could reduce spraying time spent by more than 25% compared with recommended and farmer methods.