Elm-leaf beetle.—Generally speaking one thorough and timely spraying is ample to control the elm-leaf beetle (Fig. 235). Use arsenate of lead, 1 lb. to 25 gal., and make the application to the under side of the leaves the latter part of May or very early in June in New York. Occasionally, when the beetle is very abundant, due in all probability to no spraying in earlier years, it may be advisable to make a second application, and the same may be true when conditions necessitate the application earlier than when it will be most efficacious. This latter condition is likely to obtain wherever a large number of trees must be treated with inadequate outfit.
Oyster-shell scale.—This is an elongate scale or bark-louse, 1/8 in. in length, resembling an oyster shell in shape and often incrusting the bark of apple twigs. It hibernates as minute white eggs under the old scales. The eggs hatch during the latter part of May or in June, the date depending on the season. After they hatch, the young may be seen as tiny whitish lice crawling about on the bark. When these young appear, spray with kerosene emulsion, diluted with 6 parts of water, or whale-oil or any good soap, 1 lb. in 4 or 5 gal. of water.
Pear insects.—The psylla is one of the most serious insects affecting the pear tree. It is a minute, yellowish, flat-bodied, sucking insect often found in the axils of the leaves and fruit early in the season. They develop into minute cicada-like jumping-lice. The young psyllas secrete a large quantity of honey-dew in which a peculiar black fungus grows, giving the bark a characteristic sooty appearance. There may be four broods annually and the trees are often seriously injured. After the blossoms fall, spray with kerosene emulsion, diluted with 6 parts of water, or whale-oil soap, 1 lb. in 4 or 5 gal. of water. Repeat the application at intervals of 3 to 7 days until the insects are under control.
The pear slug is a small, slimy, dark green larva which skeletonizes the leaves in June, and a second brood appears in August. Spray thoroughly with 1 lb. Paris green, or 4 lb. arsenate of lead, in 100 gal. of water.
Potato insects.—The Colorado potato beetle, or potato-bug, emerges from hibernation in the spring and lays masses of orange eggs on the under side of the leaves. The larvae are known as “slugs” and “soft-shells” and cause most of the injury to the vines. Spray with Paris green, 2 lb. in 100 gal. of water, or arsenite of soda combined with bordeaux mixture. It may sometimes be necessary to use a greater strength of the poison, particularly on the older “slugs.”
The small black flea-beetles riddle the leaves with holes and cause the foliage to die. Bordeaux mixture as applied for potato blight protects the plants by making them repellent to the beetles.
Raspberry, blackberry, and dewberry insects.—The greenish, spiny larvae of the saw-fly feed on the tender leaves in spring. Spray with Paris green or arsenate of lead, or apply hellebore.
The cane-borer is a grub that burrows down through the canes, causing them to die. In laying her eggs, the adult beetle girdles the tip of the cane with a ring of punctures, causing it to wither and droop. In midsummer, cut off and destroy the drooping tips.
Red spider.—Minute reddish mites on the under sides of leaves in greenhouses and sometimes out of doors in dry weather. Syringe off the plants with clear water two or three times a week, taking care not to drench the beds.
Rose insects.—The green plant-lice usually work on the buds, and the yellow leaf-hoppers feed on the leaves. Spray, whenever necessary, with kerosene emulsion, diluted with 6 parts of water, or whale-oil or any good soap, 1 lb. in 5 or 6 gal. of water.