Pyrethrum is used as a spray, mixing one ounce to two gallons of water, to destroy cabbage-worms and many other garden insects. If the dry pyrethrum powder is blown from a bellows into a tightly closed room, it is said to destroy all the flies.
Bordeaux mixture is made by dissolving four pounds of copper sulphate in hot water and mixing with an equal quantity of a solution made by mixing four pounds of lime with water. This is then mixed with fifty gallons of water. Paris green is sometimes added. This mixture is largely used in orchards and for destroying insects on a large scale. It is also useful for curing diseases of plants.
An excellent spray for orchards both for removing fungous diseases and scale insects is a home-made lime-and-sulphur solution. Enough for spraying a large orchard is prepared as follows:
Add three gallons of boiling water to fifteen pounds of lime. Then add ten pounds of sulphur and three gallons more of hot water. Allow this to boil about twenty minutes in its own heat, then add enough water to make fifty gallons of the mixture. Dilute with water in the proportion of one part of the solution to seventy-five of water.
Small quantities are made by using a fractional part of this recipe.
Whale-oil soap dissolved in water and used as a spray is an effective remedy for the San Jose scale.
Kerosene emulsion is used to kill the insects which suck the juices of plants and trees. It is made by mixing a half-pound of hard soap with one gallon of hot water and stirring into it, so as to mix thoroughly, two gallons of kerosene oil. This may be kept on hand for use, and is mixed with ten parts of water to one of the emulsion.
For use in large orchards force-pumps operated by compressed air and drawn by two horses are used. The spraying should be done as soon as the blossoms drop, and many orchards are sprayed three times in a season, but the work should never be done while the trees are in blossom. Vegetables should be sprayed many times through the season.
A careful study of these methods of control, adapted to the various plants and the insects which prey on them, with the natural enemies of insects encouraged and protected, would go far to prevent the wide-spread and serious damage now affecting our crops, our vegetables, our orchards, and our forests.