1961 March: Tongala (Vic). Pesticides detected: Amitrole

According to the State Rivers and Water Supply Commission in a letter to the Pesticides Review Committee 1/12/66 “”(a) no pesticide analyses are required of our department by statute. (b) Most analyses will be required in connection with stream sampling. At present only amitrole is routinely sought, but there could be some interest in diuron and dalapon in the future… (c) Total analyses last year – 47 samples of water tested for amitrole…”

State Rivers and Water Supply Commission samples were taken at weekly intervals at Swan Hill in the Murray River, and at the outfall of the Deakin Main Drain at Echuca, the major outfall of the Tongala District, which has been the largest user of amino-triazole (amitrole). Samples have also been taken from other localities, in drains or streams depending on local usage of Weedazol… (Source 10/2/69 SRWSC to PRC)

1961: In the period 14/3/61 – 23/3/61 various formulations (Weedazol 50, Weedazole Total, Weedazol T1) were applied to water couch in 12 miles of drains at Tongala and 77 samples were taken from the drains to indicate the pattern and extent of contamination…Sampling at the outfall of this system gave a maximum of 0.70ppm but a more representative figure would be 0.30ppm…. Samples taken 100 yards of operating spray teams showed levels in the range of 0 – 19.5 ppm. The average contamination level was 0.25ppm representing 20% of applied material….

1963: Over the period 16/1/63 – 1/4/63, 17 samples were taken for analysis from the Tongala drain outfall, and 25 samples from the Murray at Swan Hill…Only the control samples gave positive results. These were within 10% of the anticipated value. These samples also indicated the stability of amitrole in water over, at least a 3 week period…

Positive detections 1964/5 Deakin Drain 0.1ppm, 1965/66 Bendigo Trust Channel 0.05ppm, 1966/7 Warren’s Extension Bendigo Trust System 0.1 & 0.08ppm)