Effectiveness of a mixture of cyromazine and diazinon for controlling flystrike on sheep

Objective To determine whether there is any need for woolgrowers to add diazinon to cyromazine jetting fluid to control active flystrike on sheep.
Method Larval implants were placed on 143 sheep and allowed to develop for 2 days. Groups of 47 or 48 of these struck sheep were jetted with cyromazine at 1000 mg/L, diazinon at 400 mg/L, or a mixture of the two. After treatment, the implants were assessed daily for 3 days for the presence of feeding larvae.
Results When checked 1 day after treatment, there was a 62% reduction in flystrike in the diazinon treated sheep compared to only 12% reduction on the cyromazine treated sheep. Flystrike reduction on the sheep jetted with the mixture of cyromazine and diazinon was 69%. Three days after treatment flystrike control was 97 to 99% in the latter two groups.
Conclusion Diazinon provided a faster resolution of strikes but by 3 days after treatment there was no significant difference in the number of implants remaining active on the sheep treated with cyromazine or with the mixture of cyro-mazine and diazinon.