Modelling pesticide residues on greasy wool: surveys of the insect growth regulators triflumuron and diflubenzuron

Surveys have examined the relationship between louse and flystrike treatmen ts on farms and the resulting residues of insect growth regulators on greas y wool. These results have been summarised using a model of the on-farm sur vey data. The model estimated the amount of chemical taken up by the wool a t application. This was based on experimental breakdown rates of these inse cticides on wool determined in controlled trials. The data indicated that the backliner, triflumuron, when used off-shears wi thin 24 h of shearing, was normally applied at slightly higher than the rec ommended rate on-farm and left an average residue of 30 mg/kg greasy wool a t the following shearing 12 months later. Diflubenzuron, applied by dipping or jetting, was usually applied at lower than the recommended rates, and l eft an average residue of 40 mg/kg on the wool at shearing 12 months later. When treatment was applied to very short wool (< 3 weeks after shearing) t he residue was only about 20 mg/kg, but when applied at later times after s hearing the residue at the following shearing was not closely related to th e time of treatment. The model can be used to estimate the expected residue level and likely ran ge of results from most standard insect growth regulator treatments. This w ill improve advice to producers so most can meet specified industry standar ds.