COTTON APHID

a, Curled infested leaves; b, aphids on under side of leaf; c, aphids on stem. d, honeydew on leaf; e, winged female; f, wingless female; g, young. (a, b, c, and d, natural size; females and young, about 14 times natural size.)

COTTON APHID

The cotton aphid, also known as the cotton louse and the melon aphid, is found all over the United States. It is a general feeder on cotton, okra, melons, squash., cucumbers, and other cucurbits. It is a small, soft-bodied, sucking insect. Its color is light yellow to dark green or almost black. In Northern States, both sexes occur and eggs are laid; in the South only females that give birth to living young are known. Some adults are winged; others are wingless. The aphids spend the winter on various weeds, from which they spread to cotton in early spring. Reproduction is continuous in the South and becomes rapid during warm weather. There are no distinct broods; aphids of all sizes are present on the under side of the leaves and on the stems of plants. Lady beetles and other predators, parasites, diseases, and unfavorable weather are natural factors that help control aphids.

Aphids are present in almost every field of growing cotton. During cool, wet springs they often cause curling of the leaves, stunting of growth, or death of cotton seedlings. They do more damage later in the season by causing the leaves to curl and fall from the plants before the bolls are mature, thereby reducing the yield and grade of cotton. Aphids secrete a sticky substance known as honeydew, which drops on the leaves and bolls and gives the plants a glossy appearance. Honeydew falling on the open bolls makes the lint gummy and difficult to gin. A fungus often develops in the honeydew, which causes the plants to appear black or sooty.

Control: Heavy infestations of the cotton aphid often occur on cotton after the use of certain insecticides. Infestations may also be severe on seedling cotton where no insecticides have been applied.

The following dust treatments, which are recommended for general use against cotton insects, will usually prevent a build-up of aphids:

1. A mixture containing 3 percent of the gamma isomer of benzene hexachloride and 5 percent of DDT in every application at the rate of 10 to 12 pounds per acre.

2. A mixture containing 3 percent of the gamma isomer of benzene hexachloride and 5 percent of DDT at the rate of 10 to 12 pounds per acre in alternate applications with calcium arsenate.

3. Nicotine 2 percent in regular calcium arsenate at the rate of 10 to 12 pounds per acre alternated with calcium arsenate alone.

4. Parathion l percent in lime-free calcium arsenate at the rate of 10 pounds per acre.

5. Toxaphene at the rate of 2 to 3 pounds of the technical material per acre in every application (where toxaphene is not formulated with DDT).

When heavy infestations of the cotton aphid occur and if the need for rapid kill is indicated, the following treatments are effective:

1. Benzene hexachloride, applied as either a dust or spray, to give 0.5 pound of the gamma isomer or an equivalent amount of lindane per acre.

2. A 1 percent parathion dust applied at the rate of 12 to 15 pounds per acre.

3. Nicotine 3 percent in hydrated lime applied as a dust at the rate of 10 to 15 pounds per acre.

Another insecticide which will give quick control of heavy infestations of the cotton aphid, but which is not generally recommended because of its toxicity and low residual action, is 0.5 pint per acre of 40 percent tetraethyl pyrophosphate, or its equivalent, applied as a spray.