The amateur and beginner in fruit-growing and home-making should keep in mind the fact that about all our injurious insects may be divided into two general classes. (1. Seedling Variations) Those that have jaws for eating, such as the strawberry-worm, canker-worm, curculio, caterpillars, and beetles can be destroyed by spraying with poisons. (2. Seed Variation of Cultivated Plants) The scale insects, plant lice, true bugs, mosquitoes, and all insects with mouths fitted for sucking their food from the inner tissue of leaf, bud, or young wood must be destroyed by some application such as kerosene applied on their bodies or by some deadly gas. Kerosene in emulsion of soap has become a leading remedy, as it is about the only spray that will penetrate the scale, and it paralyzes the young insects as soon as it touches them.
In some cases it is not advisable to use poisons to destroy the gnawing insects. As an instance, the cabbage-worm cannot be attacked by poisons when the worm is most active. So gardeners use very hot water to destroy the worms and others use a repellent that the butterflies will avoid, such as water that has stood on coal tar until well scented. As the worms are slimy, others dust the worms with wheat flour that kills them by closing their pores. Hellebore powder is also used, as it kills the worms and is said to lose its strength when exposed to the air.
The currant and gooseberry worm is destroyed by large growers by spraying with weak arsenite of lime when the leaves are beginning to expand and when the leaves are about fully grown. But the amateur is apt to wait until the fruit is half grown. In this case hellebore in powder, or mixed with water, can be used as above stated. If the arsenic solution is used early it is safe, and it destroys about all other leaf-eating insects of these fruits.
The strawberry worm is checked in its work by spraying with a very weak solution of arsenic and lime if the work is done when the first scattering holes appear in the leaves. If neglected until the fruit is half grown it will not answer to spray with poison, but its work may be prevented the next season by mowing, and when dry, burning over the patch, which usually requires a sprinkling of straw. The strawberry-leaf roller is difficult to reach with poisons before the crop ripens. But spraying in August will kill the second brood and their career for the next season will be stopped. In applying the different classes of remedies the use of a standard work on spraying will prove an aid to the close-observing cultivators; such a work includes insects that only become numerous in localities over the Union.
The flat-headed and round-headed borers of fruit trees (130. Stem-borers) have been treated in times past with sprays and washes to keep the insects from the trees, but all have been failures in whole or in part. The sure treatment is to crush them in their burrows with a flexible wire as stated and use the soap wash as a repellent.