Bean Weevil

THE FOLLOWING (UNTIL OTHERWISE NOTED) IS FROM:
GERBER, H.S. 1983.
MAJOR INSECT AND ALLIED PESTS OF VEGETABLES IN BRITISH COLUMBIA.
MINISTRY OF AGRICULTURE AND FOOD.

Bean Weevil

Acanthoscelides obtectus (Say) It is mainly a pest in home-stored bean seed. Adults and larvae are found in fresh harvested and stored seed.

Vegetables attacked:

Bean, pea

Injury:

Developing larvae riddle the seed with holes causing partial or complete destruction. Unlike the pea weevil, the bean weevil breeds continuously in beans or peas in storage.

Insect:

The adult is 3 mm long, velvety, grey or brown, with pale lines on the back and has re legs. The tip of the abdomen is exposed beyond the squared-off wing covers.

Life History:

The overwintered adults emerge during bloom and feed on the foliage and seed pods. Eggs are laid in the pods. Larvae feed and pupate in the seed. In storage, eggs are laid on the seed, where generations develop continuously.

Control:

In the field, control depends on keeping the population of overwintering adults low by removing bean-plant refuse and by applying an insecticide in the spring to control adults before egg-laying begins. Plant only non-infested or fumigated seed.

Bean Weevil, Acanthoscelides obtectus (Say). It is mainly a pest in home-stored bean seed. Adults and larvae are found in fresh harvested and stored seed.

THE FOLLOWING (UNTIL OTHERWISE NOTED) IS FROM:

THE UNIVERSITY OF CALIFORNIA "IMPACT" ON-LINE PEST MANAGEMENT GUIDELINES:

SITE: BEANS INSECT: WEEVIL CONTROL: CULTURAL-CONTROL

REVIEWED: 04/89
Scientific Names:

• Cowpea weevil: Callosobruchus maculatus
• Broad bean weevil: Bruchus rufimanus
• Bean weevil: Acanthoscelides obtectus

Description of the Pest:

The adults are relatively small beetles, 0.13 to 0.2 inch in length, somewhat teardrop or triangular in shape, and dull-colored with white, reddish, or black markings. The eggs may be glued to the bean or the pod (cowpea weevil), glued to green pods (broad bean weevil), or laid loosely among beans or through cracks in the pods (bean weevil). The larval and pupal stages are spent inside the bean The cowpea weevil is perhaps the most common of the weevils in California. Infestations can begin in the field. Adults move to bean fields from trash beans left in sacks, harvesters, planters, or feed areas. The cowpea weevil readily attacks dried beans; thus this weevil can be a serious storage pest. Bean weevil infestations can also start in the field and may also originate from trash beans. As with the cowpea weevil, bean weevil will attack dried beans and can be a serious pest in stored beans. Broad bean weevil infestations also start in the field, but this pest is not a storage problem.

When to Treat:

Field survey methods have not been developed, and insecticide applications during the production season have not provided effective control.

Cultural Control:

Sanitation offers the most practical means of control. Since field infestations originate from beans, potential sources of weevils should be eliminated in production areas. Potential sources of weevils include broken sacks of seed beans left over from planting; seed beans left in planting hoppers; cull beans used in animal feed programs in a production area; small collections of beans remaining on or in a harvester following harvest; and small piles of beans remaining in or around the field after harvest.

Chemical Control:

Fumigation of beans at the warehouse site is imperative when infested beans are being brought in from the field. Fumigants are registered for this use. Fumigation of cull beans that are known to be infested may be desirable before releasing the culls for animal feed within a production area.

Reference:

Dry Beans Pest Management Guidelines V.E. Burton.
April 1989. PUBLICATION: UCPMG 19