IMPORTED CABBAGEWORM

a, Butterflies (or adults) with wings in natural positions; b, larvae (caterpillars, or "worms") ; c, pupae (chrysalids, the resting stage) ; d, cabbage plant showing typical feeding injuries. (Upper illustration: a, b, and c, about one-half natural size; d, slightly less than two-thirds natural size. Lower illustration: a, b, and c, about natural size.)

IMPORTED CABBAGEWORM

The imported cabbageworm is the larva, or caterpillar, of a yellowish white butterfly with several black spots on the wings. The velvety-green caterpillars feed on the leaves of cabbage, collards, cauliflower, broccoli, and related crops.

In the Northern States the insect passes the winter in the chrysalis, or pupal stage, from which the butterflies emerge early in the spring. In the Southern States the caterpillars may be found from March until December, or even throughout the winter.

The eggs are laid usually on the under side of the leaves. In warm weather they hatch within a week, and the caterpillars take about 15 days to mature. The change from mature caterpillar through the chrysalis to the butterfly takes place in about 10 days to 2 weeks. There are several broods each year.

Control: The imported cabbageworm can be controlled with derris, cube, or other powders containing rotenone. Apply a dust containing 0.75 to 1 percent of rotenone at the rate of 20 to 30 pounds per acre or a spray containing 0.025 percent of rotenone at 100 gallons per acre. For small plantings use 1 to 1 1/2 ounces of the dust or 1 to 1 1/2 quarts of the spray to each 50 feet of row. Begin the applications when the caterpillars appear and repeat every 7 to 10 days until the insects are brought under control. For best results apply when the air is calm, as in early morning or late afternoon. Direct the dust or spray onto the buds, or heads, of the plants and the under sides of the leaves.

Pyrethrum insecticides are less effective than those containing rotenone. But frequent and thorough applications of a dust containing 0.2 percent of pyrethrins or a spray containing 0.006 percent of pyrethrins usually give satisfactory results.

DDT will control the imported cabbage-worm and most other caterpillars that attack cabbage and related plants, but should not be applied to any leafy vegetable after the edible portion of the plant can be seen. Use a 3 percent DDT dust or 2 pounds of 50 percent DDT wettable powder per 100 gallons of spray (2 level tablespoonfuls to each gallon). Do not apply DDT on cabbage after the heads begin to form or on cauliflower after the curds begin to form (about 30 days before harvest in each case) or to any leaves that are to be eaten.