Insecticides

The use of chemicals for the destruction of insect pest had its origin with the advent of the Colorado potato beetle in our fields, about 1870.

The beetle first came to notice as a pest of cultivated potatoes in the region between the Mississippi River and the Rocky Mountains. It spread steadily eastward, and in a few years reached the Atlantic coast. It was feared at the time that the growing of potatoes was doomed, and famine was predicted.

Then the suggestion that the potato tops be dusted or sprayed with some poison chemical came up, so as to poison the pest. The remedy was found to work. And therefore was started the modern practice of using chemicals for the control of injurious insects.

Today a large proportion of our insect pests, more especially those infesting garden truck, fruits, and stored products, are controlled by some form of spraying, or by fumigation.

The primary rule governing the application of chemicals for the control of an injurious insect is to determine the feeding habits. If the pest is one that eats the foliage or tissues, in other words, if it has biting mouth parts, it may usually be killed by applying to the plant some form of stomach poison. If, on the other hand, the pest sucks the plant juices instead of chewing or eating the tissues, in other words, if it has sucking mouth parts, it is utterly useless to apply any of the stomach poisons to the surface of the plant, for they will not be taken up by the insect. The sucking beak, thrust down through the surface of the leaf, misses the poison. In this class of insects, therefore, the chemicals applied must be such as will kill the insect by contact with it, usually by entering its breathing pores.

In other words, poison sprays for leaf eating insects are applied to the plant, to be eaten along with part of the plant. Contact sprays are applied to the insect, and only incidentally to the plant, since we could not hit the one without hitting the other. With these, the great aim is to apply the material so thoroughly that it will certainly come into contact with all the insects concerned.

Examples of insects that have sucking mouth parts, and cannot be killed by poisons, but must be fought with contact sprays or by some other means, are the thrips, fleas, and the true "bugs" , such as the squash bug, plant lice, scale insects, and leaf hoppers.