Rice Weevils

How to identify Rice Weevils

Small and slender, adult rice weevils generally range in size from 2 to 4 mm. They are uniformly dark brown in colour except for their wing covers, which feature four orange spots. Their thoraxes are covered with rows of punctures that extend down their backs, save for a narrow strip in the middle. Rice weevils can fly and have prominent snouts that protrude from their heads.

Unlike adults, rice weevil larvae are white and legless. They have a wrinkled appearance and develop within whole kernels of grain. Consequently, rice weevils are rarely seen during the larval stage of development.

Signs of an infestation

Grains infested by rice weevils often increase in temperature and become noticeably heated at the surface. Rice weevil infestations also cause moisture levels to rise, resulting in grain that may feel damp to the touch. Other signs of infestation include the presence of grains with round exit holes chewed into the kernels.

Rice Weevils Removal

Infested food should be thrown away, while vacuum cleaners can be used to remove any straggling rice weevils. Specially designed traps are also available to help control rice weevils submerged in large batches of grain. Serious or highly persistent infestations require the services of a pest control professional, especially if fumigation becomes necessary.

How to prevent Rice Weevils from invading

To prevent rice weevils from infesting, grain should be stored in tightly-sealed containers made of glass, metal, or heavy plastic. The containers should be thoroughly cleaned out each time prior to adding new grain. Maintaining the cleanliness of the areas around stored grains can be helpful, as well. Stored food products should also be regularly monitored for changes in temperature and moisture content, mold, and the presence of live insects.

Habitat, Diet, and Life Cycle

Habitat

Found throughout the world, rice weevils prefer to inhabit tropical or subtropical regions. In temperate areas like Canada, the pests survive by taking shelter in protected places with plenty of food sources, such as grain elevators and similar food storage facilities. Rice weevils sometimes create outdoor infestations in fields before grains are harvested.

Diet

As their name suggests, rice weevils are often found in bins and elevators containing grains of rice. They also target barley, wheat, raw cereals, and even peas. Adult rice weevils only feed on whole grains that are intact and ungerminated.

Life Cycle/Reproduction

Female rice weevils lay about 300 to 400 eggs over the course of their adult lives, a period of time that typically covers four or five months. They chew holes in kernels of grain and deposit their eggs inside. After hatching, immature rice weevils remain housed within the grain and feed on the insides of the kernel. They develop from larvae to pupae before chewing a small, circular exit hole into the grain kernel and emerging as fully mature adults.

The length of the rice weevil life cycle is directly affected by the conditions of the surrounding environment. In warmer temperatures, rice weevils may develop from eggs to adults in a matter of weeks. Cooler temperatures, however, significantly lengthen the developmental process.

Commonly Asked Questions

General Facts

A major pest of stored grains, rice weevils are destructive invaders of pantries, grain elevators, and similar places where grain products are kept. Rice weevils are found across Canada and throughout the world. In addition to rice, they affect commodities like barley, wheat, and occasionally peas. Rice weevils are capable of destroying large amounts of grain kept in storage, especially if the environmental conditions are right and the grain has been undisturbed for an extended period of time.

Problems Caused by Rice Weevils

By developing in and feeding on kernels of grain, rice weevils have the ability to destroy large quantities of stored food products. They develop inside whole kernels or seeds as larvae and feed on these same items as adults. Rice weevil infestations can, therefore, result in significant economic losses for granaries and food storage facilities.