Anthonomus grandis

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Anthonomus grandis on a cotton boll (click on image to enlarge it)
Author(s): F. Benci, Boll Weevil Research Laboratory
Source: IPM Images

Anthonomus grandis Boheman, 1843 - (boll weevil)

The weevil is an important pest of cotton in Central and South America. It is suspected to be native to southern Mexico and Guatemala. It is found now in most areas of this continent where cotton is grown and was first recorded from the U.S.A. in 1892 and from Brazil in 1983. The weevil breeds in developing cotton bolls, effectively destroying the cotton. The spread of the weevil to the U.S.A. caused large-scale destruction of cotton crops in the beginning of the 20th century and the industry only slowly recovered through the development of pesticides like DTT. Even in the 1970s annual losses were still estimated at around US$ 200 million, with another US$ 75 million being spent on control effort. At that time about one third of all pesticides used in the U.S.A. where applied to cotton.

Vernacular names
• Deutsch: Baumwollkapselkäfer
• English: boll weevil
cotton boll weevil
• Español: picudo del algodonero
picudo del algodón
gorgojo de la cápsula del algodón
• Français: charançon américain de la capsule
anthonome du cotonnier
• Português: bicudo-do-algodão

Since 1978, the USDA Boll Weevil Eradication Program has succeeded in gradually eliminating the weevil from most of the cotton growing areas of the U.S.A., using pheromone traps, cultural methods (adjusting planting time and removing plant residues) and insecticide (mainly malathion) applications. Since 2012/13, the weevil survived in only a small area of southern Texas and operations mainly focused on monitoring efforts to confirm eradication, as well as on eliminating it from the remaining areas and from Mexico. However, eradication in southern Texas and in Mexico has proven difficult since then.

The overwintering weevils emerge in spring, feed on young cotton foliage and lay their eggs on flower buds or cotton squares, one per bud/square. The larvae feed on the flower buds or developing bolls and new adults emerge after about 3 weeks under favourable conditions. There may be up to 10 generations in one season. Infested squares/bolls drop to the ground. The adults overwinter in leaf litter and crop residues. They are good fliers and can cover 50 km or more.

The adult is around 5-6 mm long with the rostrum being about half as long as the body. The colour varies and is mainly brownish or greyish. It is densely covered with gray hairs and the pronotum has a whitish line along the middle. The front femur is swollen with double-pointed teeth on the inner margin.

For details see the respective page in Wikipedia.