BOLL WEEVIL

Cotton plant showing a, punctured squares on ground; b, square showing egg puncture; c, larva in square; d, pupa in square; e, adult emerging from square; f. larva and pupa in boll; g, adult. (a, one-fourth natural size; b, c, d, e, and j, natural size; g, six times natural size.)

BOLL WEEVIL Boll weevils pass the winter as adults in woods trash or other protected places near cottonfields. They return to cotton-fields in the spring and remain there until frost. Boll weevils prefer to feed on and to lay their eggs in squares, but they also attack bolls. Eggs are laid singly in deep punctures within the squares or bolls. After 3 to 5 days they hatch into white larvae, or grubs. The grubs feed for 7 to 14 days within the squares or bolls in which they hatch and then change into pupae. The adults emerge from the pupae in 3 to 5 days and cut their way out of the squares. After feeding on blooms, squares, or bolls for 3 to 4 days, the females are ready to lay eggs. The cycle from egg to adult weevil takes about 3 weeks. There may be seven generations a year.

The leaflike bracts at the base of squares punctured by boll weevils open up, or flare, and the squares turn yellow and die. Most of the punctured squares and small bolls are shed. Large punctured bolls are not shed, but the lock in which a grub feeds fails to develop properly, and the lint is cut, stained brown, and decayed.

Low winter temperatures and hot, dry summers help control the boll weevil. Watch for a rapid increase of weevils and severe damage during rainy periods.

Farming practices that help set bolls quickly will help control weevils. The practices are: Plant cotton on good land that has been well prepared. Use fertilizer recommended for your locality. Select an early-maturing variety suited for growing in your locality. Plant early, space closely, and cultivate frequently. Pick early and cleanly. After the cotton has been picked, stop further fruiting by plowing out, cutting, or grazing the cotton stalks as early as possible in the fall, to reduce the number of weevils in next year's crop.

Control with dusts and sprays: Benzene hexachloride, calcium arsenate, toxaphene, aldrin, and dieldrin can control the boll weevil, but when they are so used, other insect problems must be considered; infestations of the cotton aphid, the bollworm, and spider mites may develop when some of them are used alone.

The following dusts have been approved for use in some areas: (1) Benzene hexachloride to give 3 percent of the gamma isomer in the finished dust plus 5 percent of DDT (sometimes referred to as "3-5-0"); (2) calcium arsenate applied alternately with calcium arsenate plus 2 percent of nicotine; (3) calcium arsenate applied alternately with a mixture of benzene hexachloride (3 percent gamma isomer) and 5 percent of DDT; (4) lime-free calcium arsenate plus 1 percent of parathion;

(5) lime-free calcium arsenate plus 1 percent of parathion and 5 percent of DDT;

(6) toxaphene 20 percent; (7) aldrin 2.5 percent; (8) aldrin 2.5 percent plus 5 percent of DDT; (9) dieldrin 1.5 or 2.5 percent; (10) dieldrin 1.5 or 2.5 percent plus 5 percent of DDT; (11) chlordane 10 percent plus 5 percent of DDT. (This mixture is recommended only in areas where it has given good control. It has given erratic results in some areas, perhaps because of high temperatures and humidity.)

In areas where spider mites are a problem, dust formulations of organic insecticides should contain sulfur or some other suitable miticide.

The following treatments with sprays made from emulsion concentrates have given favorable results and are approved where recommended: (1) Toxaphene at the rate of 2 to 3 pounds of the technical material per acre; (2) toxaphene and DDT in the ratio of 2 to 1 applied at the rate of 2 to 3 pounds of technical toxaphene per acre; (3) a mixture to give 0.3 to 0.5 pound of the gamma isomer of benzene hexachloride and 0.5 pound or more of technical DDT per acre; (4) aldrin at the rate of 0.25 to 0.5 pound of the technical material per acre; (5) a mixture to give 0.25 to 0.5 pound of technical aldrin and 0.5 pound or more of technical DDT per acre; (6) dieldrin at the rate of 0.15 to 0.4 pound of technical material per acre; (7) a mixture to give 0.15 to 0.4 pound of technical dieldrin and 0.5 pound or more of technical DDT per acre. In areas where it has proved satisfactory and where it is recommended, a mixture of 1 pound of technical chlordane and 0.5 pound or more of technical DDT per acre may be used.

Control measures directed against the boll weevil should be applied when definite need is indicated. Except where early-season control measures are practiced, insecticides should be applied at intervals of 4 to 5 days until the infestation is brought under control. Thereafter the fields should be inspected weekly and applications made when necessary.