Part 16 (2/2)

You must be very careful in burning or you will harm the young branches with their tender bark. (3) Encourage the residence of birds. Urge your neighbors to make war on the larvae, too, since the pest spreads rapidly from farm to farm. Regularly sprayed orchards are rarely troubled by this pest.

[Ill.u.s.tration: FIG. 160. THE TWIG GIRDLER AT ITS DESTRUCTIVE WORK _a_, the girdler; _b_, the egg-hole; _c_, the groove cut by girdler; _e_, the egg]

=The Twig Girdler.= The twig girdler lays her eggs in the twigs of pear, pecan, apple, and other trees. It is necessary that the larvae develop in dead wood. This the mother provides by girdling the twig so deeply that it will die and fall to the ground.

_Treatment._ Since the larvae spend the winter in the dead twigs, burn these twigs in autumn or early spring and thus destroy the pest.

=The Peach-Tree Borer.= In Fig. 161 you see the effect of the peach-tree borer's activity. These borers often girdle and thereby kill a tree.

Fig. 162 shows the adult state of the insect. The eggs are laid on peach or plum trees near the ground. As soon as the larva emerges, it bores into the bark and remains there for months, pa.s.sing through the pupa stage before it comes out to lay eggs for another generation.

[Ill.u.s.tration: FIG. 161. BORER SIGNS AROUND BASE OF PEACH TREE]

_Treatment._ If there are only a few trees in the orchard, digging the worms out with a knife is the best way of destroying them. You can know of the borer's presence by the exuding gum often seen on the tree-trunk.

If you pile earth around the roots early in the spring and remove it in the late fall, the winter freezing and thawing will kill many of the larvae.

=EXERCISE=

How many apples per hundred do you find injured by the codling moth? Collect some coc.o.o.ns from a pear or an apple tree in winter, place in a breeding-cage, and watch for the moths that come out. Do you ever see the woodp.e.c.k.e.r hunting for these same coc.o.o.ns? Can you find coc.o.o.ns that have been emptied by this bird? Estimate how many he considers a day's ration. How many apples does he thus save?

[Ill.u.s.tration: FIG. 162. PEACH-TREE BORERS, MALE AND FEMALE Female with broad yellow band across abdomen]

Watch the curculio lay her eggs in the plums, peaches, or cherries.

What per cent of fruit is thus injured? Estimate the damage. Let the school offer a prize for the greatest number of tent-caterpillar eggs. Watch such trees as the apple, the wild and the cultivated cherry, the oak, and many others.

Make a collection of insects injurious to orchard fruits, showing in each case the whole life history of the insect, that is, eggs, larva, pupa, and the mature insects.

[Ill.u.s.tration: THE TROUBLESOME CHINCH BUG (ENLARGED) 1, bugs on plant; 2, eggs; 3, young bug; 4 and 5, older bugs; 6, long-winged bug; 7 and 8, short-winged bug]

SECTION x.x.xIII. GARDEN AND FIELD INSECTS

=The Cabbage Worm.= The cabbage worm of the early spring garden is a familiar object, but you may not know that the innocent-looking little white b.u.t.terflies hovering about the cabbage patch are laying eggs which are soon to hatch and make the dreaded cabbage worms. In Fig. 164 _a_ and _b_ show the common cabbage b.u.t.terfly, _c_ shows several examples of the caterpillar, and _d_ shows the pupa case. In the pupa stage the insects pa.s.s the winter among the remains of old plants or in near-by fences or in weeds or bushes. Cleaning up and burning all trash will destroy many pupae and thus prevent many cabbage worms. In Fig. 164 _e_ and _f_ show the moth and zebra caterpillar; _g_ represents a moth which is the parent of the small green worm shown at _h_. This worm is a common foe of the cabbage plant.

[Ill.u.s.tration: FIG. 163. THE DREADED CHINCH BUG]

_Treatment._ Birds aid in the destruction of this pest. Paris green mixed with air-slaked lime will also kill many larvae. After the cabbage has headed, it is very difficult to destroy the worm, but pyrethrum insect powder used freely is helpful.

=The Chinch Bug.= The chinch bug, attacking as it does such important crops as wheat, corn, and gra.s.ses, is a well-known pest. It probably causes more money loss than any other garden or field enemy. In Orange county, North Carolina, farmers were once obliged to suspend wheat-growing for two years on account of the chinch bug. In one year in the state of Illinois this bug caused a loss of four million dollars.

[Ill.u.s.tration: FIG. 164. CABBAGE WORMS AND b.u.t.tERFLIES]

_Treatment._ Unfortunately we cannot prevent all of the damage done by chinch bugs, but we can diminish it somewhat by good clean agriculture.

Destroy the winter homes of the insect by burning dry gra.s.s, leaves, and rubbish in fields and fence rows. Although the insect has wings, it seldom or never uses them, usually traveling on foot; therefore a deep furrow around the field to be protected will hinder or stop the progress of an invasion. The bugs fall into the bottom of the furrow, and may there be killed by dragging a log up and down the furrow. Write to the Division of Entomology, Was.h.i.+ngton, for bulletins on the chinch bug.

Other methods of prevention are to be found in these bulletins.

[Ill.u.s.tration: FIG. 165. A PLANT LOUSE COLONY]

=The Plant Louse.= The plant louse is very small, but it multiplies with very great rapidity. During the summer the young are born alive, and it is only toward fall that eggs are laid. The individuals that hatch from eggs are generally wingless females, and their young, born alive, are both winged and wingless. The winged forms fly to other plants and start new colonies. Plant lice mature in from eight to fourteen days.

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