spraying, horticultural practice of applying fungicides, insecticides, and herbicides, usually in solution, to plants. It may be accomplished by various means, e.g., the watering can, sprinkler attachment, spray gun, aerosol bomb, power spraying machine, or airplane. The spraying of powdered chemicals is called dusting. Spraying and dusting are chiefly preventive measures, but may also be used to check the spread of a pest among already infected plants. It is usually necessary for the spray to reach all exposed parts of the plant. The type of spray used and the timing of its application depend on the specific plant and its pest. Copper or sulfur compounds are common ingredients for a fungicide; nicotine, arsenic, or DDT for an insecticide. A criterion for any spray is that it does not injure the plant itself and that it is as specific as possible for the pest involved, i.e., that it inflict minimal damage to beneficial insects and to wildlife. The danger inherent in the use of poisonous sprays such as DDT cannot be overestimated, particularly in the case of those that are not eliminated or otherwise rendered ineffective (as by antitoxins) by the animals—including man—that feed on sprayed plants and insects, but accumulate in the tissues until a lethal concentration kills the animal or renders it unable to reproduce its kind. Spraying of selective herbicides is used in weed control.

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.

Learn more about spraying and dusting with a free trial on Britannica.com.

Spraying may refer to:

• The creation of a spray
• The use of a sprayer
• The use of a spray bottle
• The action of a male cat in marking its territory with urine
• Paint spraying
• Aerial application of chemicals