Spray deposit pesticide loss

Physical parameters which control the dispersion, deposit, coverage (of target plants) as well as drift losses of liquid pesticides released from aircraft In mountainous forest land are (1) spray drop size and spray formulation, (2) local meteorology, (3) local terrain at spray site and (4) type of application aircraft. 

Dispersants must always be applied with a system designed specifically for the purpose. If pesticide spray equipment is used, small droplets form that may blow away and not enough dispersant is deposited onto the oil slick. Unless suitably modified, fire monitors or regular hoses from ships may not result in correct droplet sizes or quantities of dispersant per unit area. Furthermore, the high velocity of the water/dispersant mixture can herd the oil away, resulting in the loss of dispersant to the water column, where it has little effect on oil floating on top of the water. 

The loss of pesticides due to volatilisation should not be underestimated. It has been estimated that much more pesticide is lost from its target by volatilisation than from spray drift (Anon., 1996). The pesticide formulator tends to encounter this problem when working with some soil-applied pesticides, or where a leaf deposit needs to remain on the plant surface. Pesticides taken up by foliage do not tend to suffer from this problem, as plant uptake mechanisms usually ensure that pesticide soon ceases to be available to this loss mechanism. 

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