ORGANOPHOSPHORUS RESIDUES IN WOOL GREASE RESULTING FROM SPECIFIED ON-FARM LICE AND FLYSTRIKE CONTROL TREATMENTS

Objective To investigate wool organophosphorus concentrations resultin g from a range of farm pesticide application methods. Design Random sa mpling of wool for pesticide residues and on-farm interviews to determ ine associated treatments. Procedure Tasmanian fleece wool lots were s ampled at random and tested for organophosphorus residues. The grower was identified and the pesticide treatments applied to the sheep were ascertained by on-farm interview. Results The residue concentrations s howed a large variation that was not accounted for by differences in t reatments by growers. Organophosphorus concentrations were proportiona l to the number of treatments applied, and inversely related to the ti me between pesticide application and the subsequent shearing, and were significantly influenced by the method of application. After allowing for the time of application, plunge dipping resulted in pesticide res idue concentrations 2 to 2.5 times greater than shower dipping, using spray races or hand jetting, and the use of these methods caused large r residues than the use of jetting races. Conclusions We recommend tha t plunge or shower dipping should not be used more than 7 weeks after shearing, nor at higher concentration than the standard dose rate used for lice control, whereas jetting may be satisfactory for up to 7 mon ths after shearing, provided only one application is administered.