- Volume 40 Issue 1
Residual effect of imidacloprid on brown planthopper (BPH) and residues on rice plant were investigated in pot and field tests. Residual effect (showing 100% mortality) of imidacloprid of granule formulation on the BPH lasted for 40 days at a recommended dose (0.3 kg a.i./ha) and for 30 and 20 days at a half and a quarter of the recommended dose, respectively. In case of liquid formulation of imidacloprid, the residual effect lasted for 40 days at both recommended dose (0.032 kg a.i.1ha) and a half of it, and lasted for 30 days at a quarter of it. The next generation formation of BPH was throughly depressed by the imidacloprid application at the former generation. This result supports the residual effect of imidacloprid on BPH. Seed dressing (3 ghg) showed insecticidal activity (96.7% mortality) for 55 days after treatment. When granule formulation of imidacloprid was applied to soil at a recommended dose , imidacloprid residue in leaves of rice plant increased up to 0.46 ppd for 6 days and then decreased to 0.09 ppm on 40 days after application. Residue of imidacloprid in leaves of rice plant increased up to about 0.23 ppm and about 0.2 ppm for 6 days when applied at a half and a quarter of the recommended dose, respectively and after that they decreased.