Granary Weevil Facts
Also known as the wheat weevil or the grain weevil, the granary weevil is a common pantry pest found in temperate climates across the globe. They are closely related to the rice and maize weevils.
The granary weevil is most often found wherever grain and wheat products are stored, as they are the main sources of food for both larvae and adults. If there is a large population, they can cause a great deal of damage.
Granary Weevil Bites
Granary weevils are known for destroying the grains and seeds it uses to eat, lay eggs, and develop into an adult. These pests do not sting or bite people, cause structural damage, or transmit disease. If you startle a granary weevil, its defense mechanism is to “play dead.”
Granary Weevil Infestation
Females will lay between 150 to 300 eggs during their lifetimes. These eggs are deposited into small holes in grain kernels that females drill and then seals with a waxy substance. The eggs stay in this state between four and 14 days before they hatch. Once in the larvae stage, they will continue to develop within the kernel and feed until they are ready to pupate.
Now in the adult stage, the weevil will chew its way out of the kernel, leaving a characteristically ragged exit hole. Outside the kernel, females release a sex pheromone to signal the beginning of a mating season. In all, this cycle takes between four and six weeks under warm conditions, but it can take up to 21 weeks in cooler temperatures. Their entire life cycle will last between seven and eight months.
Going without food is easy for the granary weevil. It can last a month (and sometimes more) without food. They also can’t fly to feed, but are capable of walking long distances, allowing them to further infest grain storage with ease.
Because both the adults and larvae feed on their hosts, granary weevils can be particularly destructive if they are present. You’ll find them in corn, barley, wheat, oats, rice, beans, in addition to other dried and stored foods. A tell-tale sign of their presence is the characteristic exit holes they leave in these grains. You may notice the surface of these products becoming warm and damp. This heat is a result of the motion of the insects when they are feeding. The moisture is a result of their metabolic processes. These weevils are found only where grain is stored. You won’t find them breeding in your fields.
Types of Granary Weevils
Granary Weevil Identification
Adult granary weevils vary in size. Their bodies range between two and a half to five millimeters long, with three to four millimeters being the average length, and are reddish-brown to black in color. They are covered with a few short, yellow hairs. The body of this weevil is pitted and has an irregular pattern of punctures on its thorax, and a regular, lined pattern of punctures on its wings. When the insect is walking, its antennae are often extended. This weevil is characterized by a rostrum, or snout, that extends from its head.
Granary Weevils in the House & the Garden
Granary weevils primarily target whole kernels of grain like popcorn, seeds, dried beans, decorative Indian corn, and bean bags. Keep an eye out for adult beetles crawling through these products or within your cupboards or pantry shelves.
Frequently Asked Questions
How Do I Get Rid of Granary Weevils in the Home?
Unfortunately, it is very difficult to detect the granary weevil unless it is present in large numbers. However, if you begin to notice a series of holes in these grains, they may be a sign of a larger problem.
In order to prevent them from occurring the first place, it always helps to maintain cleanliness. Always clean your storage bins and containers when you’re finished using them. Dispose of any infested food immediately.
If you’re harvesting any grain, do it as soon as possible once the crops have reached maturity. Because this weevil loves warm temperatures, you may see more of them in the summer months, which may lead to infestations.
Weevils may effectively be killed by super heating or cooling. Grains may be placed in a pan and placed in an oven at 120 degrees Fahrenheit for an hour, or frozen for four days. You can even heat them in the microwave for five minutes.
Using chemicals to get rid of these pests is not recommended because they will contaminate food. However, these may be used to supplement storage and sanitation techniques.
Benefits of Professional Granary Weevil Pest Control
A pest management professional has the education, equipment, and skills necessary to effectively address a granary weevil problem.
Finding and treating the granary weevils can be challenging, especially if they are spread throughout the grains in the pantry.
A pest management professional provides their expertise to identify the pest problem and determine the best possible solution to resolve the granary weevil infestation.
