Drift of Insecticidal Spray by Cold Air Drainage Winds in Western Mountains

摘要

Under forest mountain conditions, insecticide sample sites were located below three 20 acre (8.1-hectare) spray plots do sample drift carried out of the plots by cold air drainage winds. Samples of drift were collected on the ground and vertically upward for 200 ft (61 m). For all three plots, detectable deposits were recorded at the farthest sample site from the treated area, 2000 ft (610 m), 5000 ft (1524 m) and 7000 ft (213 m). Droplet size and number of droplets per unit area usually decreased as the distance from the plots increased. Vertically, droplet size usually decreased as height increased but, in some instances, layering appeared to occur. The study demonstrated) that cold air drainage winds carried large amounts of spray, sometimes equal to the amount that landed in the spray plots out of the target area.