Changes in diazinon concentrations in shower and plunge dip dip-wash using traditional and constant replenishment methods of dip-wash management

Summary During a research project to improve the performance and operation of shower dips, a series of measurements of the diazinon based dip-wash concentrations were taken. These measurements, although not replicated, indicated that the concentrations were falling to levels which were considered to be too low. As a result a replicated trial was conducted on the same shower dip, modified as per the findings of the previous research. The trial investigated operating the dip using (a) the conventional reinforce/replenish method and (b) using constant replenishment. This work reinforced our concerns with respect to the stripping of diazinon based dip-wash, particularly with respect to constant replenishment. A second trial was then conducted in conjunction with a dipping contractor using a diazinon based dip-wash in a mobile plunge dip using constant replenishment. Even though the contactor charged the dip and the replenishment tanks at twice the recommended lice rate (the blowfly rate), the results are concerning, not only with respect to residues in the wool and the disposal of the used dip-wash, but also with respect to lice eradication, induced chemical resistance and OH&S. Further work is urgently required to review the field performance of not only diazinon based dipwash but all current wet dip formulations using the two re-charging methods.