Cowpea Curculio
Chalcodermus aeneus Boheman, Curculionidae, COLEOPTERA


DESCRIPTION

Adult - This black weevil is humpbacked, slightly tinged with bronze, and 6 to 7 mm long.

Egg - Each oval egg is slightly less than 1 mm long. Translucent when first laid, it becomes an opaque white before hatching.

Larva - This pale yellow, brown-headed grub is legless. It is 6 to 7 mm long when fully grown.

Pupa - The pale yellow pupa, about 5 mm long, darkens as it matures. Its shape is similar to that of the adult.


BIOLOGY

Distribution - In the U.S., the cowpea curculio is most common throughout the South Atlantic and Gulf Coast States. It has been reported as far north as Maryland and Iowa, as far west as Texas and Oklahoma, and as far south as Mexico and parts of South America.

Host Plants - The cowpea curculio infests field peas, stringbeans, soybean, lima bean, cotton, and strawberry. Black-eyed pea and crowder pea are most commonly attacked. Several leguminous weeds, including vetch, are also hosts.

Life History - Cowpea curculio adults pass the winter in crop refuse or weeds, particularly brown sedge, around previously infested plants. The black humpbacked snout beetles, or weevils, leave their overwintering sites from April through July. Weevils puncture developing pods with their snouts as they feed. Females lay a single egg in some of the feeding wounds. About 4 days later, brown-headed grubs emerge and infest the seeds of beans and peas. After feeding for 2 or 3 weeks, grubs chew exit holes through the pods, drop to the ground, bore into the soil and pupate. All grubs usually leave the pods within 7 days of each other. Approximately 10 days later, a new generation of adults emerge. There are two overlapping generations each year in North Carolina.


CONTROL

Late peas or beans isolated from earlier plantings are not likely to be severely infested by the cowpea curculio. Periods of hot, dry weather also reduce the level of damage by this pest. Since this weevil migrates by crawling or flying, crop rotation and sanitation measures are valuable in controlling this pest.

Chemical control of the cowpea curculio is necessary in the commercial production of beans and southern peas. An insecticide should be applied when blooms first appear and repeated at 5-day intervals as needed. For up-to-date recommendations, consult the current North Carolina Agricultural Chemicals Manual.

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