Page:Popular Science Monthly Volume 68.djvu/221

Rh species, but they had fruited for many years, and some of them had reached a foot or more in diameter at the base. They had grown so thriftily that their continued growth was naturally expected by those who had planted them; but when the borers came the trees were everywhere injured or destroyed as by a pestilence. Within a very few years after the first appearance of those insects in that western region nothing remained of the almost numberless groves and rows of those trees except their blasted remnants and the young shoots that the vigorous and unconquered roots were striving to bring forth. That condition remains there to this day, essentially unchanged except that even the stumps and roots of the blasted trees have, from time to time, been removed to reclaim for other uses the soil which they formerly occupied. Because of that wide destruction one may now go many miles in that great region without seeing more than a few neglected outcasts of that once popular tree; just enough to afford breeding places for a few of the hardy and prolific borers, which are always ready to commit their ravages. I was an eye-witness of that great destruction from its beginning to its consummation, and afterward had unusual opportunity to observe its effects when investigating the subject of foresting the prairie soils of Iowa. Similar destruction also occurred as the borers traversed the country between their native region and the Mississippi valley, the effects of which still remain there.

The question now arises whether there is any known remedy for the attacks of those insects. Unfortunately no effective remedy of general applicability has yet been discovered. The attacks of the insects are not upon any of the parts concerned in reproduction, such as might interfere with the propagation of the tree, but upon its growing substance, which is constantly exposed at all seasons of insect activity. Therefore its inflorescence and fruitage need no protection, and proposed remedies must be applied to the surfaces of the tree and directed against some important function in the life of the insect, mainly that of reproduction. The killing of the insects in any considerable numbers seems to be quite impracticable. The few remedies which have been proposed are fluid applications which are harmless to the trees and so repugnant to the insects that they will not puncture any surface to deposit their eggs which has been so covered. But many difficulties attend the application of such remedies. The leaves and terminal portion of the twigs are doubtless too delicate for such treatment, .but the bark is not easily injured by it. The application with a brush to the bark of the trunk and branches of lime whitewash mixed with a solution of whale-oil soap has seemed to prevent the female of the borer in the beetle stage from puncturing the bark to deposit her eggs. But to be effective all such applications must carefully be made to the entire surface of the trunk and to that of the branches which have reached a couple of inches or more in diameter. They must