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Spraying. Spraying of plants as a scientific practice is, com-paratively speaking, a modern procedure, but the necessity for doingsomething to protect plants against insects and plant diseases has beenunderstood since antiquity. In their writings the Greeks, Romans,and Hebrews noted the existence of rusts and mildews, and the plagueof locusts is of Biblical record. Spraying is only one of several ways of protecting plants and amongthe others may be enumerated hand picking, fumigating, banding,burning, using fungous diseases as insecticides, crop rotation, soilsterilization and various other more or less practical methods. Theseother methods are important when understood and put into practiceat the right moment and in the right way, but they are inexact com-pared to spraying and are seldom as efficient. Spraying, by whichis meant the use of chemicals to poison or otherwise exterminateanimal and vegetable parasites on plants, has been reduced verynearly to an exact science in this country, largely within the lastcentury, and, while it is not the purpose here to go too deeply into thisart, some broad rules may be laid down and some little understoodpoints cleared up. |
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