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What Is a Grain Weevil?

Updated Oct 17, 2022

Updated Oct 17, 2022

Home > Pest > What Is a Grain Weevil?

If you open your cupboard to see a strange, long-snouted insect scurrying for cover, you might have a weevil problem. While these tiny bugs look like something off of an alien planet, they have been infesting our granaries since ancient times. This article will take a closer look at the grain weevil, its fascinating history, and review some effective prevention and removal methods.

Different Kinds of Weevils

Weevils are common pests and beetles belonging to the Curculionidae family (order Coleoptera), with over 97,000 species worldwide. Weevils are pervasive grain pests, primarily feeding on different crops, from rice to cotton, wheat, carrots, barley, and much more. Since weevils are one of the largest beetle families, they come in countless shapes, sizes, and colors. But all weevils have elongated snouts, called rostrums, along with small (around a quarter of an inch) bodies. A weevil’s color can range from brown to green, blue, white, yellow, black, and red, often accompanied by splotches or dots.

Weevils have been infesting human food stores and lowering grain quality for thousands of years. Some of the earliest evidence of weevil infestations is in Egyptian tombs dating back to 2300 B.C. They have also been found in Amarna stables from the 14th century B.C.

If you’re dealing with a weevil infestation, you’re most likely up against “stored product” weevils. Stored product pests infest sealed fruits, nuts, grains, pasta, cereals, and the like. Weevils are a common stored product pest, along with pantry flies, several moths, and other types of grain beetles. Pantry pests can be a nuisance to manage, multiplying quickly and becoming an infestation while destroying your dry goods. Thankfully, while unpleasant to deal with, weevils are not known to carry any diseases, won’t bite, and don’t damage your home.

If you find a weevil in your pantry, you’re most likely dealing with one of three common species, the maize weevil, rice weevil, or granary weevil.

Maize and Rice Weevils

rice weevil
Image Source: Canva

Maize weevils (Sitophilus zeamais) and rice weevils (Sitophilus oryzae) are close cousins and similar in appearance and behavior. They’re extremely small, even by weevil standards, only growing to three thirty-seconds inch in length. Their color ranges from dark to reddish-brown, rust, and black, sometimes accompanied by yellow or red dots. They both possess shiny pits along their carapace and antenna along their rostrum. Adults possess the ability to fly, equipped with a pair of small, fully functioning wings. While they get their names from infesting maize and rice, respectively, homeowners can find them in:

  • Wheat
  • Dried peas
  • Oats
  • Cereal
  • Pasta
  • Beans
  • Birdseed
  • Sunflower seeds
  • Grapes
  • Stored cotton
  • Pears
  • Apples

Granary Weevil

granary weevil
Image Source: Canva

The granary weevil (Sitophilus granarius), or wheat weevil, is slightly larger than rice and maize weevils, about 2.5-5.0 millimeters in length. It has a long, cylindrical body with dark brown to black coloration. It has an elongated head with a more sharply curved snout than other weevils. It also lacks the ability to fly and is not attracted to light.

Granary weevils infest dried grains and cereal products, including:

  • Corn
  • Rice
  • Cereal
  • Macaroni
  • Spaghetti
  • Oats
  • Barley
  • Rye
  • Various seeds
  • Buckwheat
  • Beans
  • Grain sorghum

The Life Cycle of the Weevil

One of the most frustrating things about weevils is that they lay their eggs inside grain kernels. A weevil infestation typically begins with one of these egg-bearing kernels. Your dried goods may already have one inside, or a weevil will sneak into a container and lay eggs. The egg then pupates inside the kernel and hatches into its larval stage. These weevil pupae look like small, fleshy, maggot-like grubs. The weevil larvae will feed on surrounding grain products for about three weeks before maturing. They’ll then seek out new grain to lay eggs.

During their life cycle, weevils may never leave a single package of grain products unless disturbed or trying to migrate to another nearby package. As a result, weevils can be extremely difficult to detect until you open a pack of pasta, only to find a swarm of small invaders.  

How Do You Prevent Weevils?

Sometimes, it can be impossible to prevent weevils, like if you buy a product containing an infested kernel. However, these situations are highly unlikely, and your best bet is to prevent adult weevils from getting in and laying eggs. Here are some of the best steps you can take to prevent pests from raiding your pantry:

  • Thoroughly inspect all purchased wheat and grain products: Weevils can come to infest storage facilities or warehouses. In these situations, weevils can cut small holes and burrow into packed items. When shopping, always carefully inspect the outside of the container, looking out for small holes. 
  • Keep your kitchen and pantry clean: Keeping a clean kitchen is a good homeowner habit and a valuable pest control practice. A messy kitchen and pantry will attract all manner of pests, weevils included. Be sure to clean your kitchen often, and we recommend fully cleaning out your panty at least once a month.
  • Keep entry points into your home sealed: Weevils, like most pests, can enter the home through small openings. We recommend doing a yearly outdoor home inspection at the end of summer, sealing all cracks and crevices, and replacing weather stripping and screens.
  • Store food in airtight containers: Weevils have small, chewing mouthparts within their snouts. These cannot inflict bites but can slowly chew through paper, cardboard, and plant matter. Keeping your dry food in plastic containers makes them functionally weevil proof.
clean pantry
Image Source: Canva

While harmless to humans and homes, weevils can be an irritating nuisance. They’re extremely difficult to detect early and can quickly spread to overtake a whole pantry. If you encounter weevils in your home, you can easily dispose of them using the following methods:

  1. Remove all infested products from your pantry: If you see weevils crawling on or inside a dry good, dispose of it immediately.
  2. Throw away all other unsealed dry goods in your pantry: If you find weevils in one item, odds are they have infested every unsealed product in your pantry. If you have any dry goods that are not sealed, you’re better off throwing them away. Anything kept inside a sealed container or plastic bag is fine. If your dry goods are sealed, thoroughly check the outside of the container. The item has to go if you spot any small holes, tears, or breaks in the seal.
  3. If you’re unsure about a product, freeze it: If you find a bag or box of grains that you are unsure about or suspect weevils may have gotten into, you may be able to salvage it by freezing its contents. Leave it sealed inside the freezer for one week, and it should kill any eggs and larvae that might be inside.
  4. Clean, sterilize, and repackage: After removing everything from the pantry, your next step is cleaning and sterilizing it. Start by vacuuming all the dust, dirt, and debris from the floors and shelves. Then clean and disinfect the shelves with hot soapy water, vinegar, or other food-safe cleaners. Abrasive cleaners like bleach or ammonia are unnecessary, and you should avoid using insecticides and pesticides as most are ineffective against weevils. After everything has been cleaned and had a chance to dry, place all items back inside the pantry.

Closing Thoughts

Weevils, while an annoying nuisance, are functionally harmless. They carry no diseases and do not possess the ability to bite. Furthermore, if detected early enough, you must remove them and clean the infected area. While weevils rarely warrant the services of a pest control company, in some cases, infestations can become too large to handle for homeowners. These large-scale infestations typically occur on farms where large amounts of grain are stored or inside abandoned homes.

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