Characteristics of Fipronil Solution Deposition on PaddyRice (Oryza sativa) Leaves

Characteristics of fipronil solution deposition on leaves of paddy rice (Oryza sativa) were studied. Deposition of fipronil solution on rice leaves increased significantly with the increasing of nozzle orientation and with the decreasing of droplet size. Deposition of fipronil solution on rice leaves treated with spray angle of 30°,45° and 60°,increased by 16.6％,39.3％ and 70.1％ comparing to that on vertical leaves,respectively. Deposition of fipronil solution treated in droplet size (VMD) of 157.3,193.2,215.4 and 233.7 μm decreased by 16.2％,39.1％,49.5％and 66.4％ comparing to that treated in smaller droplets of VMD 149.5 μm. Approximately 25.6％ to 28.1％ of the solution applied was deposited on rice leaves when treated in a spray volume less than 339 L/hm2,while it declined greatly in higher spray volume. The maximum retention of the solution on rice leaves was approximately 1.42 μL/cm2. As a function of organic silicon applied as spraying adjuvant at the dosage of 150 g/hm2,deposition of fipronil solution on rice leaves was improved by 80％~150％ comparing to that without the adjuvant in treatments of smaller droplets and less spraying volume combination,however,it wasn't increased when treated in combination of large spray volume (694.5 L/hm2) and coarse droplets (VMD 233.7 μm). The results indicated that,the deposition of pesticide solution on rice leaves would be improved greatly if it's applied in relatively small droplets and less spraying volume in spraying angle of 45°~60°,and by adding of organic silicon as spray adjuvant.