There are now several thousand different kinds of insects that may be classed as injurious in the United States and Canada. Over 600 kinds were exhibited at the Columbian Exposition in 1893. All of these may not be injurious every year, as most insect pests have periods of subsidence, when certain factors, possibly their enemies or perhaps climate conditions, hold them in check. The outlook for American horticulturists, so far as injurious insects are concerned, is not encouraging. Nowhere else in the world are insects being fought as intelligently, successfully and scien-tifically as in America, yet we never have exterminated, and it is very doubtful if we ever will, a single insect pest. This means that American horticulturists will never have any fewer kinds of insects to fight. On the contrary, there are many more insect pests now than in our grandfather's early days, and new pests are appearing every year. This alarming state of affairs is largely due to two causes, for both of which man is responsible. Man is continually encroaching upon and thereby disturbing nature's primitive domain and the equilibrium which has there become established between animals and plants.

In consequence, insects like the Colorado potato beetle, the apple-tree or the peach-tree borers have been attracted from their original wild food-plants to man's cultivated crops, which often offer practically unlimited feeding-grounds. Most of the new insect pests, however, are now coming to America from foreign shores. American horticulturists are continually importing plants from the ends of the earth, and oftentimes the plants are accompanied by one or more of their insect pests. Some comparatively recent introductions of this kind are the sinuate pear-borer, the pear midge, the gypsy moth, the brown-tail moth, the horn-fly and the elm leaf-beetle; such standard pests as the Hessian fly, the cabbage butterfly, the currant-worm, the codlin-moth (Fig. 1296) came in many years ago. Of the seventy-three insects which rank as first-class pests, each of them almost annually causing a loss of hundreds of thousands of dollars, over one-half have been introduced from foreign countries, mostly from Europe. It is a significant fact that usually these imported insects become much more serious pests here than in their native home; this is doubtless largely due to the absence of their native enemies, to more favorable climatic conditions here, and to a less intense system of agriculture in this country.

Most of our worst insect pests of the fruits, of the garden crops, of the granary, of the household, of the greenhouse, and practically all of our most dangerous scale insects, are of foreign origin. Man will continue to encroach on and disturb nature's primitive domain, and commercial operations will never cease, nor is there much hope of ever effectually quarantining our shores against these little foes; hence there seems to be no practicable way to stop this increase of the insect enemies of the horticulturist. The one who is the best fitted by nature, and who best fits himself with a knowledge of these pests and how to fight them, will usually be the one to survive and reap the reward of profitable crops. No part of a plant, from its roots to the fruit it produces, escapes the tiny jaws or the sucking beaks of insects.

Ground beetle. One of the commonest predaceous insects.

Fig. 1310. Ground beetle. One of the commonest predaceous insects.

Moths of the peach tree borer. The lowest one is male.

Fig. 1311. Moths of the peach-tree borer. The lowest one is male.

Root-Feeding Insects

Many of the small fruits and vegetables are often seriously injured by insects feeding on the roots. The grape-vine fidia (the grub of a small beetle) and the grape phylloxera plant-louse five on grape roots. Strawberries often succumb to the attacks of the grubs of several small beetles known as strawberry-root worms, and to the large white grubs of the May beetles. The roots of cabbages, radishes and other cruciferous plants are often devoured by hordes of hungry maggots. These underground root-feeding insects are difficult pests to control, like any other unseen foe. Sometimes they can be reached successfully by injecting a little carbon bisulfide into the soil around the base of the plant. The cabbage maggots can be prevented largely by the use of tarred paper pads placed around the plants, or by pouring a carbolic acid emulsion at the base of the infested plants. The strawberry root-feeders are best controlled by frequent cultivation and a short rotation of crops.