State University Extension
Home Maintenance And Repair - 01500524
Grain and Bean Weevils
Several types of weevils, including the rice, granary, maize and
bean/pea weevils, can be encountered in the home. They are all pests of
whole grain foods such as nuts, beans, cereals, fruits and seeds.
The true weevils (rice, granary and maize weevils) have a long snout on
the head. The rice weevil is about 3 mm long dark reddish brown, with
four pale spots on the upper surface. The rice weevil can fly and is
attracted to lights. The granary weevil is slightly larger (4 mm), of
the same body style and entirely dark chestnut-brown. It cannot fly and
is not attracted to lights. The maize weevil is also slightly larger
than the rice weevil, and it is very dark reddish-brown or black with
four yellowish spots. All of these weevils infest whole grain rice,
barley, corn, wheat, popcorn, sunflower seeds, nuts, beans and bird
seed. They will also attack hard cereal products such as macaroni, dry
pet food, cereals and caked flour.
The larvae are white, legless, and feed inside of the whole kernel or
seed - hence they are rarely seen. Weevil damaged grains typically are
hollow and have small, round emergence holes. The life cycle requires
about 4 weeks and there may be three to five generations per year.
The bean weevils are not true weevils; they are members of the closely
related bean weevil family. Their body shape is more round than the
rice, granary and maize weevils and they do not have the slender
protruding snout of these true weevils. The common bean weevil is about
1/8 inch (3 mm) long with the upper surface mottled shades of gray.
These feed on dried beans, leaving perfectly round holes in the beans.
Very often, beans are harvested from the garden which look perfectly
good. However, there can be been weevil larvae present inside. These
larvae can continue to develop while the beans are in storage, with
adults emerging during winter. Many a housekeeper has been dismayed
to find a good supply of beans ruined by this insect. Heating the beans
to 130 degrees F for 1/2 hour prior to storage will kill any larvae
present and arrest any further development. A small number of dried
larvae in the beans does not constitute any hazard to health.
Integrated Pantry Weevil Management
Purchase susceptible foodstuffs in quantities that can be used in a
short time: 2-4 months, if possible. When purchasing packaged food, be
certain the containers are not broken or unsealed and that there are no
signs of infestation. Check the packages for freshness dates. Once food
is in the home, use older packages before newer ones, and opened ones
before unopened ones. Storing dried foods in a freezer will prevent
insect development. Keep food storage and preparation areas clean at
all times; spilled and exposed food attracts insects.
If granary, rice or maize weevils are found in the kitchen, a search of
all possible food sources should uncover the source of infestation.
Disposal of infested grains and a thorough cleanup of the area should
For bean weevil control, all that is required is to remove the infested
beans and clean up the storage area. This pest does not infest as wide
a range of stored goods and an insecticide is not recommended.
For a complete listing of suggested control options for all home, yard
and garden insect pests contact your local Extension Service, found
under local government in the phone book.
Read and follow instructions on the pesticide label. Heed all warnings.
Check with your physician if you have any concerns regarding your
personal health risk. Revised by Tom Ellis, M.S., Department of
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This information is for
educational purposes only. References to commercial products or trade
names does not imply endorsement by MSU Extension or bias against those
not mentioned. This information becomes public property upon
publication and may be printed verbatim with credit to MSU Extension.
Reprinting cannot be used to endorse or advertise a commercial product
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employer. Michigan State University Extension programs and materials
are open to all without regard to race, color, national origin, gender,
gender identity, religion, age, height, weight, disability, political
beliefs, sexual orientation, marital status, family status or veteran
status. Issued in furtherance of MSU Extension work, acts of May 8 and
June 30, 1914, in cooperation with the U.S. Department of Agriculture.
Thomas G. Coon, Director, MSU Extension, East Lansing,MI 48824. This
information is for educational purposes only. Reference to commercial
products or trade names does not imply endorsement by MSU Extension or
bias against those not mentioned.
information.was reviewed as
of June 2008. For more information about the contents please
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