The annual loss in the United States to vegetable crops from the depredations of insects and diseases amounts to millions of dollars. Practical growers, economic entomologists and plant pathologists believe that most of the losses could be forestalled by taking the proper preventive measures. In too many instances, however, the grower makes no preparation for control and when the pests appear it is impossible to secure a spraying outfit and materials before great damage has been done.
In the control of fungous diseases and insect pests of the garden, preventive measures are of prime importance. Spraying is often necessary, but it is expensive and should not be employed ordinarily until all other practical means of prevention have failed. Single cropping or the want of proper rotation frequently causes trouble. When a crop pays unusually well, the temptation is to continue its cultivation upon the same ground for years—a practice which harbors insects and diseases.
Diseased or infested seed or stock often introduce enemies. This is a strong argument in favor of the home production of seeds and plants. When plants are kept in a thrifty condition there is reduced danger of serious loss from both insects and diseases. Judicious fertilizing, cultivating and watering may be worth far more in warding off attacks than any amount of spraying. Infested soils when used in starting plants become a source of contamination. Too much care cannot be exercised in the selection of soil known to be free from disease germs.
The use of contaminated manure may also introduce diseases. Plowing and cultivating at just the right time often prove effective preventive measures; and clean tillage and the destruction of refuse after harvesting crops may be the means of avoiding serious losses.