Weevils: What to Know

A. What Are Weevils? 

Weevils are small beetles with long, narrow snouts — a characteristic of insects belonging to the Curculionidae family. Many species of weevil are agricultural and household pests. They are found on crops, plants, or stored cereal grains.

What do weevils look like? Weevils are small bugs about 0.125 to 0.25 inches or 3 to 6 millimeters long. They are shaped like tiny pears or light bulbs. They have a long and slender snout in front of their head. They have six legs and folded antennae. Some weevils have wings, and others don’t. 

Weevils are usually reddish-brown to black. Some weevils have reddish or yellowish colorations or patterns on their wings. They have hard-shelled bodies with tiny holes or pits. They are commonly found in gardens and fields. 

What do weevils eat? Weevils are pests that feed on crops and the roots of plants. They grow in cereal grains like corn, wheat, oats, rye, buckwheat, and rice. They also feed on legumes like beans or peas, nuts, cotton, and wheat products like flour. They also infest grapes, apples, and pears.

A weevil’s life cycle. A weevil’s life cycle includes the egg, larva, pupa, and adult stages. Female weevils lay their eggs inside a grain kernel or on plants. They lay small, white eggs in clusters. The eggs hatch into weevil larvae, which feed on the grain. Larvae look like small, white or yellowish worms.

A larva grows inside the grain kernel and matures into a pupa. It forms a cocoon and changes, or undergoes metamorphosis. Within a month, the weevil eats through the seed coat and emerges as an adult. Adults have a hard covering or exoskeleton and wings. They can fly. The adults mate and lay eggs to begin the cycle again.

The lifespan of a weevil can vary based on environmental factors like the temperature and availability of food. Some weevils may live for a few months. But on average, their life cycle lasts a year.

B. Types of Weevils

There are many weevil species. Some of them include rice weevils, granary weevils, and root weevils.

Rice weevils. Rice weevils infest stored grains. They are reddish-brown and have four reddish or yellowish markings on the covers of their wings. Adult rice weevils can fly and are attracted to light.

Granary weevils. These weevils resemble rice weevils and infest stored grains and grain products. They can be longer than rice weevils and are reddish-brown to black. Unlike rice weevils, they don’t have markings, can’t fly, and aren’t attracted to light.

Root weevils. They grow on the roots of plants. Some root weevils chew the leaves of shrubs. Root weevil species include strawberry root weevil, black vine weevil, and lilac root weevil.

C. Where Do Weevils Come From? 

Weevils are found worldwide. They are commonly seen in gardens and fields. They often crawl into your house through openings or cracks in doors, windows, or the foundation. They enter buildings to look for shelter in hot and dry weather conditions. They live in warm and moist places. You may see them in sinks, water basins, or bathtubs.

Weevil infestation can occur when you bring already infested food home. It can also occur if weevils enter your house through open cracks and then enter food containers.

D. Signs You Have Weevils

You can easily spot a weevil infestation. If you notice a decrease in the weight and quality of stored grains, they’re probably infested by weevils. This is because weevil larvae and adults feed on grain. 

Infested grain may have a white, sawdust-like appearance due to weevil droppings. Grain and grain products damaged by weevils have holes in them. It’s where the adult weevils emerge from.

E. Why Do You Get Weevils? 

Weevils are attracted to warm, moist environments. They emerge in late spring and seek shelter in the hot, dry months of June and July, looking for places to reproduce and lay their eggs. If they enter your home, they get attracted to grain and other food and infest them. If you get weevil-infested food, heating it to room temperature can promote rapid growth of weevils, causing infestation.

F. Health Risks of Weevils

Are weevils harmful? Weevils are not harmful to humans, pets, houses, furniture, or clothing and don’t carry any diseases. They are temporary nuisance pests that damage stored food products. If weevils infest a garden or field, they can damage plants and reduce crop yields. Otherwise, they are harmless and go away on their own. 

Do weevils bite? Weevils don’t bite or sting you. They only feed on plants and food material.

G. How to Get Rid of Weevils

Here are some ways to get rid of weevils.

Root weevils. You can control root weevils with insecticide sprays like bifenthrin, cyfluthrin, cyhalothrin, or permethrin. They are sprayed on the base or lower part of plants. This stops the weevils from climbing up and damaging crops or plants. Spray the insecticide later in the day just before weevils become active.

Weevil larvae grow in soil in the summer months. You can add beneficial Heterorhabditis nematodes or roundworms to control the growth of weevils. But ensure that you water the soil in the treated area to keep it moist.

Rice and granary weevils. To control rice or granary weevil infestation, dispose of the infested grain. Keep the uninfested food in sealed, airtight containers made of metal, glass, or heavy plastic to prevent infestation. You can also store the food in the refrigerator or freezer to keep it fresh. Freezing the grain at 0 degrees Fahrenheit for three days can prevent weevil growth.

You can also save the uninfested grain by heating it to 140 degrees Fahrenheit for 15 minutes. Extreme temperatures can stop the growth of weevils in all stages of their life cycle. 

Empty and clean the cupboards or shelves holding infested food with warm soap water. Caulk any cracks in your house that may attract weevils. Insecticides or pesticides may not help with weevil infestation. Also, avoid spraying pesticides near stored food. 

To get rid of large quantities of weevil-infested grain, you can opt for professional pest control and fumigation.