Propetamphos: a comparison of three formulations in preventing blowfly strike in sheep.

A trial was conducted in an area where organophosphate resistance to the green blowfly of sheep, Lucilia curpina WIED had been reported. Three formulations containing Propetamphos, namely an oil based pour-on, a grease based smear-on, and an emulsifiable concentrate were applied to 300 sheep in an attempt to compare the protection that this insecticide afforded, in preventing progressive blowfly strike. One hundred sheep were furthermore treated with an insecticide growth regulator, Cyromazine as a treated control group and a further 300 sheep were exposed as an untreated control group in order to monitor the level of blowfly strike in the area. It was found that the grease-based formulation protected the animals for 2 weeks against blowfly strike, both the pour-on and the emulsifiable concentrate formulation for 3 weeks, while the insect growth regulator afforded 4 weeks protection. It was concluded that if organophosphate resistant blowfly were present, the length of protection might be dosage related and that blowfly strike in sheep was almost equally controlled by Cyromazine and Propetamphos.