Rice Weevil and Maize Weevil

Maize Weevil image provided by Pat Porter

Article author: Janet Hurley, Bradleigh S. Vinson
Most recently reviewed by: Pat Porter (2018)

Common Name(s): Maize weevil, Rice Weevil

Description

Rice weevils and maize weevils are about 1/8 inch long and brown. They have densely spaced pits on the pronotum that are round (maize weevil) or elongated (rice weevil). The two species look almost identical without magnification. Both are internal feeders, which means the larva develops inside whole grain kernels. Mating often occurs within 24 hours of adult emergence from grain kernels. this weevil has well developed wings and is considered a strong flier. This ability allows them to travel from field to storage facilities. Inside warehouses they can fly great distances to infest food products.

Origin and Distribution

Rice and maize weevils are usually found in grain storage facilities or processing plants, infesting wheat, oats, rye, barley, rice, and corn. Although not often found in the home, they are sometimes found infesting beans, birdseed, sunflower seeds, dried corn, and too a lesser degree macaroni and spaghetti. These weevils do not bite, nor do they damage wood or furniture.

Habitat & Hosts

These insects have chewing mouthparts. They can be in stored grains of all types including wheat, corn, oats, barley, sorghum, macaroni, and other grain products. They may also infest grain in the field. Larvae hollow out kernels of grain and usually attack whole kernels. Holes in the side of the grain are made by adults and by the emerging adults. They build up in numbers in stored grain.

Life Cycle

Females can lay 300 to 400 eggs typically one per cavity. Larvae develop through several stages (instars) inside the grain kernels and also pupate inside the kernel. They may complete a generation in a month in warm conditions. Adults often live for 7 to 8 months and some records are over 2 years.

Management

If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

Monitoring using sticky traps, pitfall traps, or pheromone traps will help with proper identification. In the home, control of these insects involves inspection and removal of infested food products, discarding the heavily infested material, re-packaging material in new containers, and vacuuming kitchen cabinets. Products that need to be retained may be placed in the freezer for several weeks to kill adults and larvae. However, in most cases if it’s not fit for consumption the materials should be disposed of. In larger infestations of stored grain warehouses and silos, remediation will require emptying the infested areas, cleaning and the use of residual insecticide.