Standard methods of applying pest-control chemicals and other compounds to plants, animals, soils, or agricultural products. For spraying, chemicals are dissolved or suspended in water or, less commonly, in an oil-based carrier. The mixture is then applied as a fine mist. In dusting, dry, finely powdered chemicals may be mixed with an inert carrier and applied with a blower. In fumigation, gases or the vapours of volatile compounds are held in contact with the materials to be treated. Sprays and dusts are used to control insects, mites, fungi, and bacterial diseases of plants; disease-spreading insects, such as lice and flies, on animals; and weeds. They are also used to apply mineral fertilizers, to increase or decrease fruit set, to delay the dropping of nearly mature fruits, and to defoliate plants to facilitate harvesting (e.g., of cotton; see defoliant). Sprays adhere to treated surfaces better than dusts do. Fumigation may be used to control insects and some diseases in stored products or to control insects and sometimes fungi and weeds in soil. Increasing use of spraying and dusting has prompted concern over their impact on the environment, the food chain, the water supply, and public health. New chemicals and precautions have only partially allayed these concerns. Seealso crop duster; fungicide; herbicide; insecticide.
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