Field life of the insect growth regulator, diflubenzuron, on lucerne

Abstract The residual life of the insect growth regulator, difiubenzuron, applied as a wettable powder spray to growing lucerne (Medicago sativa L. cv. Wairau) in February, has been measured. For single spray applications of 20–100 g/ha applied in the first week of the trial, initial residue levels were 1.8–8.5 mg/kg. The first and second half-lives were 3 and 4 days respectively, whereas the third half-life was over 15 days. Residues of 0.3–1.5 mg/kg remained 22 days after application. Dilution of the chemical appeared to be caused more rapidly by herbage growth than by chemical degradation. In multiple spray trials with applications of 20–100 g/ha at weekly intervals, the disappearance rate fell off significantly towards the end of the trial period when the herbage growth was less. The multiple sprays gave increasing residue levels throughout the trial period, with residues of 3.2–23.5 mg/kg at 8 days following the fourth spray. A simplified procedure for the analysis of diflubenzuron residues on plant ...