Ar. Gilmour et al., The uptake and depletion of fenitrothion in cattle, pasture and soil following spraying of pastures for locust control, AUST J EX A, 39(8), 1999, pp. 915-922
Fenitrothion is an organophosphorus insecticide widely used for the control
of locusts in Australia and overseas. It is sprayed on swarms and bands of
locusts and on the pastures on which they feed. However, there is little A
ustralian data on depletion rates of fenitrothion when used this way. Conse
quently, there has been concern that beef cattle producers may not be able
to guarantee that their cattle meet legal requirements with respect to resi
due levels following grazing on sprayed pasture. This paper reports a study
conducted in February 1998 in central western New South Wales on the rate
of depletion of fenitrothion in cattle, pasture and soil after fenitrothion
spraying. The cattle were 18-month-old heifers in forward store condition.
Fenitrothion was detected in the fat of 7 of the 66 exposed cattle. Residu
es in 2 of these exceeded the Maximum Residue Limit of 0.05 mg/kg. No fenit
rothion was detected in the fat of the 26 cattle slaughtered 14 days or lat
er after treatment or in muscle and liver samples. The half life of fenitro
thion was 2-3 days in the soil and 1-2 days in the pasture. We conclude tha
t the 14-day slaughter withholding period currently approved by the Nationa
l Registration Authority is appropriate.