New Georgia Encyclopedia: Boll Weevil

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Boll Weevil

The boll

Boll Weevil

weevil greatly affected Georgia's long history of cotton production between 1915, when the insect was introduced to Georgia, and the early 1990s, when it was eliminated as an economic pest. The adult boll weevil measures from three to eight millimeters from the tip of the snout to the abdomen, which is half the length of its body. Its color is usually reddish or grayish brown but may vary according to age and size. A distinctive characteristic is the double-toothed spur on the inner surface of each front leg. A newly hatched larva is inconspicuous, and the mature larva is white, legless, and about thirteen millimeters long. Larvae complete development in cotton fruiting structures.

Yield losses associated with the boll weevil reduced cotton acreage from a historical high of 5.2 million acres during 1914 to 2.6 million acres in 1923. Although insecticides provided temporary relief, the cotton industry remained unprofitable, and planted acreage continued to decline, to a low of 115,000 acres in 1983. In 1987 Georgia growers began participating in a program to eradicate the boll weevil. Over a period of years the program proved successful, and Georgia producers have increased cotton acreage and yields significantly while reducing their dependence on insecticides.

Before

Boll Weevil

eradication the boll weevil was the chief pest of cotton in Georgia as well as in other areas of the cotton belt. The primary damage to cotton occurs when female boll weevils deposit eggs in fruiting structures (flower buds, or squares, and seed pods, or bolls) on developing cotton plants. Upon hatching, the boll-weevil larvae or grubs feed in the square, causing it to be shed by the plant or rendering the bolls unsuitable for harvest. Intensive use of broad-spectrum insecticides for boll-weevil control often caused outbreaks of other insect pests, because these insecticides cause the destruction of natural enemies, such as parasites and predatory insects, that suppress various pest species in cotton. Selective insecticides often target an individual group of insects; for example, some insecticides control caterpillar pests and do not harm predators or parasoids. Dependence on insecticide is often referred to as a "pesticide treadmill."

Several

Boll Weevil Trap

biological factors made it possible to eliminate the boll weevil. Most significant is that the boll weevil can reproduce on only one plant species in Georgia—cotton. Theoretically, if all boll weevils were controlled in all fields, they would be eliminated. The boll-weevil trap has played an integral part in eradication. A detection device was needed so that fields infested with boll weevils could be identified. Cultural practices for boll-weevil management, or non-insecticide means of reducing risk or avoiding particular insect infestations, include early planting, stimulating rapid plant growth and development with appropriate fertility and weed-management programs, and using early-maturing varieties. In addition to the use of such cultural practices as stalk destruction after harvest, which eliminated plant hosts for reproduction, infested fields were treated with the insecticide malathion. All cotton growers in Georgia are required to participate in the Boll Weevil Eradication Program (BWEP).

Since elimination of the boll weevil as an economic pest, insecticide use in cotton has been reduced by approximately 75 percent, and yield losses associated with insects have been reduced by 50 percent. The most damaging and frequent insect pests Georgia growers encounter today are bollworm and tobacco budworm (both caterpillar pests that feed on squares and bolls). Others include the cotton aphid, beet armyworm, cutworm, fall armyworm, tarnished plant bug, cotton fleahopper, soybean looper, stink bugs, thrips, and whiteflies. Modern Georgia cotton producers take an integrated approach to insect management, using such natural controls as predatory bugs to suppress pest populations. Insecticides remain a critical component of insect-management programs but are used only on an as-needed basis on in-field pest populations.

The BWEP is an ongoing program, as boll-weevil reinfestation continues to be a threat to the cotton industry. Cotton growers pay an annual assessment on each acre of cotton planted to monitor for and eliminate reinfestations if they occur. Boll weevil traps can be commonly observed on the perimeter of Georgia cotton fields during late summer and early fall. For the Georgia cotton industry, the BWEP has been a tremendous success from both an environmental and an economic perspective.