Granary Weevils

Image via flickr by Sleepy Claus

As with many types of beetles, weevils do serve a purpose to the environment but are pests in regards to stored foods and other kinds of goods. Weevils can be used as a biological control mechanism against invasive plants. They are also noted to help with the natural process of decomposition.

It’s when weevils, such as granary weevils, invade your home and begin to take up residence in your pantry that they become a nuisance. Granary weevils will enter your home through open doors, windows, or through infested foods bought at the grocery store. Equipping yourself with knowledge of what these critters are and how to keep them out will help you avoid costly losses of stored foods.

What Is a Granary Weevil?

Granary weevil is their common name, but in actuality, they are wheat weevils. These weevils are known for contaminating food stores. They prefer to eat grains and products such as corn, wheat, oats, macaroni, Kaffir seed, sorghum, buckwheat, and barley. This wide range of foods that they like to eat contributes to their ability to infest grocery stores and homes, as they start in places where these grains are stored and then travel through the supply chain within the infested products.

Female granary weevils can lay up to 300 eggs at a time; she will eat a hole in a grain kernel, lay a single egg inside, and then seal it closed with a waxy substance. In 14 days or less, the eggs will hatch. In the larva stage, they will eat the meat of the grain from the inside until they are ready to pupate. 

Once the weevil has developed into an adult, they will eat their way out of the grain kernel. Newly developed females will release pheromones, and males will respond to begin the mating process. The timeframe in which all of this takes place within a warmer climate is four to six weeks. In colder climates, the same process can take up to 21 weeks. The life cycle of the granary weevil averages between seven and eight months.

What Do Granary Weevils Look Like?

Adult granary weevils have a moderately cylindrical body and measure from 2 to 5 millimeters in length. The head is extended and has a distinguished snout that reaches down from its head. This protrusion is roughly one-fourth as long as a granary weevil’s body. Adults range from a reddish-brown to black and have oval pits in their thorax. Though this weevil has wings that are protected by ridged wing-covers, they are not capable of flight.

The granary weevil larva resembles a grub; they are white, legless, soft, and somewhat fleshy; as they mature, they will develop into pupae and eventually adults if the process isn’t interrupted.

Where Do Granary Weevils Live?

Granary weevils are found wherever grains and wheat are stored. They won’t be found in the fields but will make their home in silos, warehouse, packaged foods, and your pantry. When they have infested a grain or wheat farm’s stored products, they can be tough to eliminate.

Since they lay their eggs inside of grain kernels, the grain itself is their homes. When there is adequate food, they have no reason to move to another location. Granary weevils can’t fly but can travel long distances if necessary to find a fresh supply of grain to call home. Granary weevils can go for a month without food, giving them time to travel when necessary for survival.

Problems With Granary Weevils

Granary weevils are notorious for the potential agricultural destruction they can cause. They have made a place for themselves in history by earning the title of being among the most formidable pests on the planet. They can be devastating to farms that produce, store, and sell grains. The damage they cause can be near-catastrophic to those whose livelihoods depend on successfully harvesting, maintaining, and providing quality grains.

The main problem with granary or wheat weevils is that once they have infested grain stores, they are often distributed throughout the supply chain to grocery stores and ultimately to your home. Granary weevils can wreak havoc on all of your stored foods and contaminate your entire pantry if they are left unchecked; this can cost you time, money, and the inconvenience of having to eradicate a granary weevil infestation from inside your home.

If both granary and larva weevils are present, the damage they cause will be expedited, because they both eat stored grain foods. Signs that there is a healthy weevil population in your stored foods are the insects themselves and the heat and moisture they produce as they feed and process foods. Help from a professional pest control agency may be necessary if you have a severe enough granary weevil infestation in your home.

Granary Weevil Control Solutions

Taking preventative measures to avoid having issues with granary weevils invading your pantry is suggested. You will need to be sure that you have correctly stored your grains and other foods in your pantry to prevent weevils from gaining access to them. This includes using storage containers that are made specifically to prevent granary weevils and other insects from potentially infesting your pantry.

Sometimes you may unknowingly introduce granary weevils into your pantry by bringing infested products into your home from the grocery store. If you find that this is the case, you will need to remove all contaminated products and thoroughly clean the affected areas to ensure that you have entirely removed the eggs, larvae, and adult weevils. As a final precaution, you can use insecticides in the crevices and cracks of your pantry and cupboards to eliminate any weevils that may be in hiding.

Granary weevils are one of the most common grain infesting pests for a reason, and that is because they are resilient and hard to eradicate when they have established themselves. As with many unwanted pests, taking the time to learn how they are brought into your home and how to get rid of granary weevils will pay off in the long run. Granary weevils are just one of a long line of pests that are best left outside.  


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