Facts, Identification & Control
Callosobruchus maculatus (Fabricius)
The cowpea weevil is about 2 to 5.4 mm long. It is brownish with black markings on the wing covers. The wing covers do not cover the entire abdomen, and a black marking is visible on the end of the abdomen as well.
Behavior, Diet & Habits
The cowpea weevil, Callosobruchus maculatus (Fabricius), is a pest of stored beans. As the name suggests, it infests cowpeas. This beetle has also caused damage to stored soybeans. It is a member of a group of beetles called Bruchids. Other Bruchids, including the pea weevil, Bruchus pisorum (Linnaeus) and the bean weevil, Acanthoscelides obtectus (Say) are also pests of stored beans.
Cowpea weevils are known as “internal feeders.” The female deposits eggs on the developing pod or on the surface of stored beans. The larvae bore into the bean and begin to eat. A seed can support more than one larva at the same time. The larvae stay inside the bean during the entire life cycle and emerge as adults. If beans are stored in a warm, humid place, the life cycle can be completed in as little as three weeks.
Adult cowpea weevils will lay eggs on the same beans where they developed.
Signs of a Cowpea Weevil
As the infestation grows, some of the adults may fly toward the windows. These adult weevils at the windows and the beans with holes are signs that there is an infestation. Infestations in homes can come from beans grown in the garden or from packaged beans from a store.
Eliminating an infestation of cowpea weevils in a home begins with a careful inspection. Find all of the food that shows insect activity. Discard all of the infested products. Vacuum the pantry and cabinet shelves thoroughly to be remove any adult insects. Store new products in sealed containers to prevent future cowpea weevil problems.
Insecticide application is the final step. The object is to treat the cracks and crevices where insects might hide. Any insects that escape the treatment can start a reinfestation, so it is advisable to have a pest control professional make the application.