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Boll Weevil

CROP IMPACTED: Cotton

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Family: Curculionidae

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About Boll Weevil

Boll Weevil is a North American cotton pest. It was introduced to the United States from Mexico in the 1890’s. It was a huge agriculture problem, taking a multiyear eradication campaign to control them. By 2013 Texas was the only state that still had infested areas of Boll Weevil.

Boll Weevil Reproduction and Life Cycle

Female boll weevils can deposit between 100 to 300 eggs into cotton buds and/or fruit, but will not lay eggs in areas where other females have deposited their eggs, unless the majority of cotton bolls are infested. It takes about 2 to 3 weeks for the eggs to develop into adults, meaning that there can be up to 10 generations of boll weevils each year. The larvae live their entire development within the cotton boll, destroying all the seeds and surrounding cotton fibers.

Boll Weevil Identification and Habitat

Identification

The identification of a mature boll weevil varies depending on the food it has during its larval stage, but on average they are about 3 to 8.5 mm long, including its curved, long snout, which is about half its body length. During spring, adult boll weevils emerge from a partially dormant state. A distinctive characteristic of an adult boll weevil is the double-toothed spur on the inner surface of both front legs. The eggs that female boll weevils produce are pearly white, oval and about .85 mm long. The soft shell allows the egg to fit into almost every cavity. The newly hatched larva is only slightly larger than the size of its egg. As the larva matures it is white, with its mouthpart and head being brown in colour. It has no legs, is about 13mm long and its body is wrinkled and curved. During the pupa stage of the boll weevil life cycle, they are white developing into a brown colour.

Habitat

The only host plant the boll weevil lives and feeds on is cotton plants. The severity of infestation and damage is greatly dependent on the temperature throughout the winter months. Plants are injured by both larvae and adult boll weevils.

Boll Weevil Control Methods

To have satisfactory control is dependent on using an integrated management system that includes the use of cultural and chemical methods.

Cultural Control

It is recommended that cultural control practices include early planting, stimulating fast and efficient growth by properly prepared seed beds, adequate fertilization, weed control practices and planting early maturing adapted varieties of cotton. Due to the large infestation of boll weevil and it’s difficultly to control, it is important to have good crop rotation and crop diversification. Other good cultural control programs include early detection of cotton stalks, cleanup of ears that are in hibernation of boll weevils, early planting, seed treatment and cotton varieties that are early to mature and have rapid-fruiting. The main objective of these cultural control practices is to rush the development of cotton plants so the plants are set before boll weevils become established and abundant.

Chemical Control

The timing of chemical control of boll weevil is very important. Due to the fact that the boll weevil larvae spend their entire developing period inside cotton bolls, the application of insecticides would be greatly ineffective at this time. For optimal insecticidal control would include both an in-season and diapause application. In-season application should be based on weekly boll weevils counts and damage and is done to control the weevils during the major period of boll maturity and fruit set. The first application of insecticides should be done when 10% of the squares are punctured. For the most part, insecticides are used to reduce the overwintering of boll weevils. This practice is used to delay the need for in-season application the following year. When needed, treatments should start at the beginning of diapause and continue until the fields no longer have food for boll weevil. Application of a chemical called defoliant near the end of the season speeds up harvesting and damages the crop residue as early as possible, resulting in the eradication of the food source for the remaining boll weevils.

Latin / Alternative Boll Weevil Names

  • -Anthonomus grandis

Sources

http://www.britannica.com/animal/boll-weevil

http://ipm.ncsu.edu/AG271/cotton/boll_weevil.html