The bronze birch borer is destroying many fine white birch trees in some parts of the country. Its presence is known by the dying of the top of the tree. There yet is no known way of preventing this borer from attacking white birches, and the only practicable and effective method so far found for checking its ravages is promptly to cut and burn the infested trees in autumn, in winter, or before May 1. There is no probability of saving a tree when the top branches are dead, although cutting out the dead parts may stay the trouble temporarily. Cut and burn such trees at once and thus prevent the spread of the insect.
Bud-moth on apple.—The small brown caterpillars with black heads devour the tender leaves and flowers of the opening apple buds in early spring. Make two applications of either 1 lb. Paris green or 4 lb. arsenate of lead in 100 gal. of water; the first when the leaf-tips appear and the second just before the blossoms open. If necessary, spray again after the blossoms fall.
Cabbage and cauliflower insects.—The green caterpillars that eat cabbage leaves and heads hatch from eggs laid by the common white butterfly (Fig. 295). There are several broods every season. If plants are not heading, spray with kerosene emulsion or with Paris green to which the sticker has been added. If heading, apply hellebore.
The cabbage aphides, small mealy plant-lice, are especially troublesome during cool, dry seasons when their natural enemies are less active. Before the plants begin to head, spray with kerosene emulsion diluted with 6 parts of water, or whale-oil soap, 1 lb. in 6 gal. of water.
The white maggots that feed on the roots hatch from eggs laid near the plant at the surface of the ground by a small fly somewhat resembling the common house fly. Hollow out the earth slightly around every plant and freely apply carbolic acid emulsion diluted with 30 parts of water. Begin the treatment early, a day or two after the plants are up or the next day after they are set out. Repeat the application every 7 to 10 days until the latter part of May. It has also been found to be practicable to protect the plants by the use of tightly fitting cards cut from tarred paper. (See page 187.)
Canker-worms.—These caterpillars are small measuring-worms or loopers that defoliate apple trees in May and June (Fig. 217). The female moths are wingless, and in late fall or early spring crawl up the trunks of the trees to lay their eggs on the branches. Spray thoroughly once or twice, before the blossoms open, with 1 lb. Paris green or 4 lb. arsenate of lead in 100 gal. of water. Repeat the application after the blossoms fall. Prevent the ascent of the wingless females by means of sticky bands or wire-screen traps.
Case-bearers on apple.—The small caterpillars live in pistol-shaped or cigar-shaped cases, about 1/4 in. long. They appear in spring on the opening buds at the same time as the bud-moth and may be controlled by the same means.
Codlin-moth.—The codlin-moth lays the eggs that produce the pinkish caterpillar which causes a large proportion of wormy apples and pears. The eggs are laid by a small moth on the leaves and on the skin of the fruit. Most of the caterpillars enter the apple at the blossom end. When the petals fall, the calyx is open and this is the time to spray. The calyx soon closes and keeps the poison inside ready for the young caterpillar’s first meal. After the calyx has closed, it is too late to spray effectively. The caterpillars become full grown in July and August, leave the fruit, crawl down on the trunk, and there most of them spin cocoons under the loose bark. In most parts of the country there are two broods annually. Immediately after the blossoms fall, spray with 1 lb. Paris green or 4 lb. arsenate of lead in 100 gal. of water. Repeat the application 7 to 10 days later. Use burlap bands on trunks, killing all caterpillars under them every ten days from July 1 to August 1, and once later before winter.
Cucurbit (cucumber, melon, and squash) insects.—Yellow, black-striped beetles appear in numbers and attack the plants as soon as they are up. Plant early squashes as a trap-crop around the field. Protect the vines with screens (Fig. 229) until they begin to run, or keep them covered with bordeaux mixture, thus making them distasteful to the beetles.
Squash vines are frequently killed by a white caterpillar that burrows in the stem near the base of the plant. Plant a few early squashes between the rows of the late varieties as a trap-crop. As soon as the early crop is harvested, remove and burn the vines. When the vines are long enough, cover them at the joints with earth in order to develop secondary root systems for the plant in case the main stem is injured.