Measurement of insecticide drift—A comparison of two methods

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Abstract
DDT/superphosphate dust was applied in a light wind to a target area of short, dry pasture at a rate equivalent to 1.7 lb pp -DDT/ac using a spinner-type fertiliser spreader. Analysis of fertiliser collected on trays snowed that at least 8 per cent of the total DDT applied drifted off the target in a cross wind of approximately 2 knots. Analysis of pasture cut immediately after top-dressing indicated that only about 3 per cent of the total DDT applied lodged above stubble height and that nearly half of this was outside the target area. The pattern of spreading of the top-dressing machine indicated that the rate of DDT application over a large area could have varied from 0.7 to 4.0 lb/ac. The significance of these results in relation to the agricultural use of insecticide dusts is discussed. A prediction equation of the form p.p.m. DDT (pasture) = k (mg DDT/tray) was derived. The observed values of k and b were 21.5 and 0.57 respectively. It is suggested that k would be dependent on the condition of the pasture but that b would be reasonably constant for a given insecticide formulation.

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