These are the larvae of several different kinds of insects, which burrow into and feed upon the inner bark, the solid wood, or the interior pith of the larger roots, trunks, branches, and stems or stalks of many horticultural plants. Nearly every kind of fruit trees is attacked by its special kind of borer, as are also many of the smaller vine and bush-fruits and garden crops. Borers are often the most destructive of insect pests. The two apple-tree borers, the round-headed (Fig. 1316) and the flat-headed species, and the peach-tree borer (Fig. 1311) doubtless cause the death of as many apple and peach trees in America as all other enemies combined. The fruit-bark beetles, or "shot-hole" borers, usually attack only unthrifty or sickly fruit trees, and a tree once infested by them is usually doomed. Two borers, one the grub of a beetle and the other the caterpillar of a moth, sometimes tunnel down the stems of currants and gooseberries. Raspberries and blackberries (Fig. 1317) also suffer from two or thee kinds of borers, one working in the root, one in the stem, and a maggot bores down and kills the new shoots. A caterpillar closely allied to the peach-tree borer fives in squash vines, often ruining the crop. The potato-stalk weevil sometimes does much damage in potato fields.

Sometimes one can prevent borers from getting into a fruit tree with a paper bandage closely wrapped around the part liable to be attacked, or by the application of some "wash." Most of the washes recommended will prove ineffectual or dangerous to use. Gas-tar has given good results, but some report injury to peach trees from its use; hence one should first experiment with it on a few trees. No way has been found to keep borers out of the small fruits or garden crops; usually if infested canes, stems or plants are cut out and burned early in the fall or whenever noticed, most of the borers will be killed. When borers once get into fruit trees, the "digging-out" process is usually the only resort, although some report that they readily kill the depredator by simply injecting a Utile carbon bisulfide into the entrance of his burrow and quickly closing it with putty.

Mouth parts of a biting insect.

Fig. 1312. Mouth-parts of a biting insect.

San Jose Scale. Showing the mature winter scale; also the insect itself, with its threadlike feeding organs.

Fig. 1313. San Jose Scale. Showing the mature winter scale; also the insect itself, with its threadlike feeding organs.

Hemipterous insect. Known to entomologists as a true bug.

Fig. 1314. Hemipterous insect. Known to entomologists as a true bug.

Tomato worm attacked by parasitic insects.

Fig. 1315. Tomato worm attacked by parasitic insects.