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.
See bulletins of the U.S. Dept. of Agriculture.