How to Kill Grain Weevils

Grain weevil larvae turn into adults inside the grain kernel and emerge through exit holes.
Grain weevil larvae turn into adults inside the grain kernel and emerge through exit holes. (Image: Hemera Technologies/ Images)

Grain weevils (Sitophilus granarius), also called snout weevils, plague stored grain products. They can easily become a pantry pest if not controlled. One female can produce up to 250 eggs during her eight-month life cycle. The female deposits her eggs within a grain kernel. The adult grain weevil feeds on the outer surface of grain kernels, but the larvae actually reside inside the kernel and feed on the fleshy part.

Things You'll Need

  • Flashlight
  • Plastic bag or air-tight container
  • Pan
  • Stove top
  • Freezer
  • Synergized pyrethrins

Video of the Day

Inspect grain products during the night using a flashlight. Quickly shine the flashlight onto the product to detect the grain weevil's presence.

Dispose of all infested foods in an air-tight container or a sealed plastic bag to kill the grain weevils. Place the bag or container in the garbage or bury outside in the soil.

Fill a pan with the infested grain products. Heat to 120 degrees Fahrenheit for one hour.

Store the heated grain in the freezer at 0 degrees Fahrenheit. Let the grain remain in the freezer for four days before removing to successfully kill the grain weevils.

Spot-treat grains to be planted outside with synergized pyrethrin dusts or sprays. Make sure the synergized pyrethrins product clearly states it can be used on grain products for the control of grain weevils. Follow the directions on the label for application instructions.

Tips & Warnings

  • Store grain products in air-tight containers.
  • Purchase whole grain products in small quantities in case they are infested with grain weevils.
  • Examine grain products closely for any signs of infestation after purchase.
  • Diatomaceous earth can kill adult grain weevils in grains used for planting.
  • Never treat grain products that are intended for food consumption with pesticides.


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