What are bean weevils?

Identifying bean weevils

Seeing beetles suddenly in your kitchen? You may have bean weevils. Bean weevils are small beetles measuring about one-sixth of an inch in size. They have a rounder body with six legs and folded antennae. They can be an olive-brown color with brown or gray spots on their wing covers, and their thorax is covered with fine yellow-orange hairs.

Where do bean weevils live? The answer may be a little closer to home than you may like. Bean weevils infest whole beans and other legumes where they thrive and reproduce. That can include dried beans and legumes in your kitchen pantry.

What are the signs of a bean weevil problem? The first indication of an infestation is often the presence of numerous flying weevils. A bag, box, or storage bin of beans may be so infested that weevils are forced to leave the container in search of a new place to lay their eggs. Bean weevils “play dead” when disturbed and may take up to five minutes to resume movement. This behavior can make it challenging to detect weevils in beans at first glance.

Bean weevils vs. bean beetles

Bean weevils, scientifically known as Acanthoscelides obtectus, are actually a type of seed beetle and part of the bruchinae family. Seed beetles are known to infest various kinds of seeds or beans and can spend a significant portion of their lives inside a single seed, where they feed and develop.

What is the difference between bean bugs like the bean beetle and a bean weevil? First, the name “bean beetle” is usually used to refer to Callosobruchus maculatus, also known as cowpea weevils or cowpea seed beetles. While they share the ability to infest legumes with bean weevils, bean beetles have a slightly different appearance. They have a small, rounded body that is reddish-brown with black and gray markings.

The bean weevil life cycle

The bean weevil life cycle begins when a female bean weevil deposits her eggs on bean pods in a field or on whole beans in storage. Each female lays up to 60 eggs in her lifetime, and numerous whitish eggs can be seen on a single bean. Bean weevils are internal feeders, meaning the tiny, grub-like larvae bore their way into the bean. Several larvae may feed inside each bean, and a considerable portion of the bean’s interior is consumed. It is the larvae that do the damage. Adults do not feed.

Upon maturity, the larvae pupate near the surface of the bean and then emerge from the bean, leaving numerous holes in the bean. The entire life cycle can last from 21 days or as long as 80 days. Populations of bean weevils develop quickly in stored beans where suddenly hundreds or thousands of weevils are seen crawling or flying in infested rooms. What keeps their population in-check in nature? In the wild, some larger insects, as well as birds or rodents will eat weevils or weevil-infested seeds or legumes.

Are bean weevils dangerous?

Are bean weevils bad? Yes, they are definitely considered pests, but weevils in beans are not dangerous to humans. Bean weevils do not bite people and are more likely to either flee or play dead when disturbed. If you find bean weevils in your home, it's important to remove the infestation and discard any infested items to prevent them from spreading. However, you are not likely to become sick from bean weevils, as they do not pose any health risks to humans.

On a commercial scale, bean weevils present a more significant problem due to their ability to rapidly consume and infest crops and dried stored legumes. Their presence can lead to substantial economic losses for farmers and producers, as weevils damage stored food supplies and reduce crop yields. Despite their negative impact, bean weevils can serve as a food source for certain predators, so they do have their place in natural ecosystems. However, their overall impact is largely negative, especially in agricultural settings where they threaten food production.

Tips for bean weevil control and prevention

While Terminix does not cover bean weevil extermination in our general pest control plans, there are steps you can take against bean weevils. The control of any stored product pest involves many steps, the primary of which is the discovery of infested food items or other sources of infestation (e.g., food spillage accumulation). When bean weevils are present, all items containing or made of whole beans need to be examined. Usually, bagged beans in the pantry are the source, but some decorative items are made of or contain whole beans, so such items should not be overlooked. How do you get rid of bean weevils for good? Consider the following to remove or prevent an infestation:

• Discard infested foods in outdoor trash. Infested decorations (flowers, wreaths, etc.) should also be discarded.

• Freeze suspect foods at zero degrees Fahrenheit for six days.

• Clean cabinets and shelves where infested foods are stored by vacuuming and using soap and water.

• Store all dried food goods, including dried pet foods and birdseed, in a glass or plastic container with a tight lid. If weevils are in that food product then the infestation will be contained and not spread to other foods.