Enemies of a special section.
In the section east of the Mississippi river and north of the gulf states, the average insect losses affecting the medium- to large-sized hard-wood trees of the woodlot and small forests evidently equal, or even surpass, the average losses to the same class of timber by forest fires. The hickory bark-beetle has killed a large percentage of the hickory ; the black locust has been so badly dam aged by the borer that in some sections where the conditions are otherwise most favorable for the growth of this valuable tree, it is rendered practi cally worthless ; the heart-wood of some of the finest specimens of oak and chestnut is often so badly damaged by timber worms that it is value less for anything but fuel or rough boards. While the pines and spruces suffer more perhaps from fire than from insects, especially the young growth, there are certain insects, as the white pine weevil, which often cause serious damage. Thus we see from these four examples alone that the insect problem is by no means the least important to be considered by the farmer in the management of his wood lot.
There are also local problems, like those pre sented in Massachusetts and adjoining states by the gypsy moth and brown-tail moth, which are already demanding attention through federal, state and private effort and the publication of information.
Controlling special cases.
It may appear at first that the problem of con trolling the more common and widely distributed insect enemies of forest trees is difficult and expen sive, when, in fact, it is often just the reverse. A few special cases are cited to demonstrate this point.
The hickory bark-beetle (Scolytus quadrispinosus) is a short, stout, shining, black or brownish beetle, averaging about one-eighth of an inch in length, which attacks the medium to large hickory trees in the spring and summer, and girdles them by ex cavating egg galleries and larval mines (Fig. 488i under the bark. The undeveloped brood passes the winter in the bark, and the matured brood of adults flies in May to August to continue the depredations. To control an ont br eak of this pest it is neces sary that all, or at least a large .
percentage of t h e hickory trees within a radius of a few square miles that die from any cause in the sum mer, be felled and utilized for fuel, or other purposes, or be burned, to kill the over-win tered broods. The work must be done in the period begin ning with about the first of October and ending with the first of May. To prevent further trouble, living hick ory trees for a n y purpose should be cut in the spring and summer, so that the tops and unused part s of t he trunks may be utilized by the beetles as breeding places and thus serve a s traps, when they can be destroyed the following winter by burning. [For further information, see Yearbook, United States Department of Agriculture, 1943, pp. 314-3171 The locust borer (Cyllene robinier, Fig. 489) is a whitish, elongated, round-headed grub, which hatches from an egg deposited by a black-and yellow-striped long-horned beetle, found on the trees and on the flowers of goldenrod from August to October. The eggs are deposited in August and September in the outer bark on the trunks and branches, and the young larvie pass the winter in minute hibernating cells between the outer corky bark and the living bark. In the spring they bore through the inner bark and enter the wood. Their presence is indicated in May, June and July by the boring dust lodged in the bark and around the base of the infested trees.
The young hibernating borers may be killed from November 1 to April 1 by spraying the infested trunks and branches with kerosene emulsion, one gallon to two gallons of water. The older borers,
after they have entered the wood, may be destroyed in May to July by cutting out the worst infested trees and burning them or immersing them in streams or ponds. The cutting of locust for any other purpose, however, should be done between November 1 and April 1, so that the removal of the bark from the utilized part of the trunk and the burning of the tops will kill the young borers before they enter the wood. New plantations should be made where the locust is naturally free from general injury, and seed for the purpose should be from trees which show the least dam age. [For additional information, see Bul letin No. 58, Parts I and III, and Circular No. 83 of the Bureau of Entomology, United States Depart ment of Agriculture.] The oak timber worm (Eupsalis nti nuta) is a slender, whitish, cylindrical grub or worm, less than an inch in length, with the seg ments toward the head much enlarged, and the last abdomi nal segment smooth an d rounded. These worms hatch from eggs deposited in wounds in the bark and wood of living trees, and at first bore almost invisible holes directly into the wood. The burrows are enlarged and extended in all directions through the heart-wood until the larvw have attained their full growth. (Fig. 490.) They then transform to adults within their burrows and emerge the next spring or summer to repeat the cycle in the same wounds or in the wood of dead trees, stumps and logs, either standing or felled. An axe wound in a large healthy tree may result in attack by this insect, and later the entire heart-wood become perforated with so called pinhole defects. Wounds made by lightning or other cause may result in the wood of the entire trunk being thus rendered worthless for stave timber, clapboards or first-class lumber. This insect breeds in great numbers in the stumps of dead trees and in the stumps and logs of felled trees, and is ever ready to attack living trees wherever a slight wound in the bark offers an opportunity. To avoid the attack of this in sect on living trees, all injured or dead hard wood trees, as well as the logs of felled ones, should be promptly utilized or burned, and newly felled trees should be cut very close to the ground and the brush tops burned over the stumps. Indeed, the disposal of all places for the breeding of this insect will always be an important feature in the management of American hard-wood forests and farmers' woodlots. [For additional information, see Yearbook, Department of Agriculture, 1903, pp. 323, 324 and Bulletin No. 35, West Virginia Agricultural Experiment Station, p. 294.] The chestnut timber worm (Lymexylon sericeum) is somewhat similar in general form to the pre ceding, but is at once distinguished by the dark brown, horny plate with toothed edges on the last segment of the body. It hatches from an egg deposited by an elongated, brownish beetle clothed with fine silky hairs. The habit of this borer is practically the same as the oak timber worm, except that it is found principally in chestnut, though it sometimes infests red oak and white oak. It is exceedingly destructive to the heart-wood of old chestnut trees (Fig. 491), and never fails to enter the slightest wound in the bark on the trunks and around the bases of the dead branches of liv ing trees. It also breeds in dead or felled trees, stumps, and the like, so that the method of control is practically the same as that recommended for the oak timber worm, especially as applied to chestnut and red oak.