Anthonomus grandis

Scientific Name Anthonomus grandis
Common Names English: Mexican cotton boll weevil; German: Mexikanischer Baumwollkapselkäfer; Spanish: Grillo de la cápsula del algodonero; French: Charançon du cotonnier
Description A typical curculionid (snout beetle), with its prolonged head and geniculate antennae. The adult is about 6 mm (0.24 inch) long, brownish in color and covered with fine gray hairs.

Biology

Damage

The first signs of attack are small punctures on the sides of the bud, which are caused by feeding or egg-deposition. The larvae develop in buds and young capsules. The bracteoles spread prematurely; later, the buds or small bolls turn yellow, become brown and finally drop off with the larvae inside. Large punctured bolls may not fall off, but they will be of very poor quality.

Lifecycle

Under favorable conditions, the life cycle lasts only about three weeks, so up to seven generations per year are possible. Adults of A. grandis grandis overwinter mostly under forest litter, on volunteer or re-growth cotton plants, or on wild Malvacean hosts. Those of some other subspecies may also hibernate in their larval cells. In the spring, eggs are laid into developing buds, and later in the season into young bolls, too. Only one larva develops in each bud.
The larvae hatch after 3-5 days and feed for 7-12 days, then pupate. Three to five days later, the adult beetles emerge and leave the flowers or bolls. They feed on cotton leaves for a further 3-7 days, then mating occurs, after which the females start laying eggs.

Occurrence

Additional Crop Information

Cotton (Gossypium hirsutum and G. barbadense) and some other Malvaceae.

Agricultural Importance

Anthonomus grandis is widespread in all cotton-growing areas of North America . It is one of the most costly pests in the US. It has recently been spread to South America (e.g. Brazil).

Control

Integrated Crop Management

The immature stages are sensitive to heat and desiccation. Therefore, plant residues should not be ploughed under, as this will bring weevils into a moist and dark environment, but should instead be removed from the field, thus leaving the remaining larvae or pupae exposed.

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