Bacterial degradation of the acaricide amitraz

Abstract

This thesis describes dip tank field trials and laboratory investigations on the acaricide Amitraz. Amitraz is a triazapenta- diene compound which is relatively unstable in fouled dip washes. The field trials were conducted on the farm Sea View according to the "Total Replacement Method" and on the farm Sea Ways according to the "Lime Stabilization Method" of dipping. The results of these trials showed that Amitraz was stable in clean dip washes, and under conditions of high pH resulting from the addition of slaked lime to the dip wash. Using mixed bacterial populations optimum conditions for degradation of Amitraz in the laboratory were determined. Bacterial cultures degraded Amitraz most efficiently in media supplemented with yeast extract or with a high content of sterile cattle faeces. Amitraz concentrations were determined by gas chromatography. A culture. efficient at degrading Amitraz was enriched from a dip tank sludge inoculum. From this culture ten bacterial isolates were identified; nine of these were of the genus Pseudomonas and one was an Achromobacter sp. Experiments with both mixed and pure cultures demonstrated that bacterial degradation of Amitraz was by the process of co-metabolism. The existence of four degradation products was shown using thin layer chromatography. Tentative identification of two of the products was made.