Rice Farming

Beware Of
Weevils & Beetles

Insect pests can significantly
devalue stored grain

By Perry Nettles

With grain prices at all time record highs – $8.00-a-bushel corn, $9.00-a-bushel wheat and $24.00-a-hundredweight rough rice – it is important to protect today’s stored-grain commodities.

For example, a 100,000-bushel bin of rough rice, figured at the standard rate of 45 pounds per bushel, would have a value of $1,080,000 and could be infested with numerous stored-product pests. A seriously infested grain bin can have its value decreased by as much as two-thirds, wreaking havoc on an already volatile market.

Today’s farmers, elevators and millers can no longer afford to be uninformed about the pests that are destroying their investments. This article focuses on three of the major stored-product pests that cause the largest financial impact on stored grains.

Rice and granary weevils
Adult rice weevils are about 1/8-inch long and reddish brown to black with four reddish or yellowish spots on the wing covers (elytra). Adult granary weevils look similar to the rice weevils, but without the spots on the elytra. The head bears a slender snout and the shield behind the head (pronotum) has course round punctures. The elytra have deep lines and course punctures.

The rice weevil is one of the most serious stored-grain pests worldwide. This pest originated in India and has been spread worldwide through commerce. It now has a cosmopolitan distribution and is a serious pest in the southern United States. Both the adults and larvae feed on whole grains. The adult rice weevil is attracted to lights and can fly. When disturbed, adults pull in their legs and feign death. The adult female eats a cavity into a seed and then deposits a single egg in the cavity, sealing in the egg with secretions from her ovipositor. The larva develops within the seed, hollowing it out while feeding. The larva then pupates within the hollow husk of the grain kernel. Finally, it emerges as an adult amongst the grain it grew in.

Red and confused flour beetles
Adult beetles, about 1/4-inch long, may live for more than three years. Eggs, larvae and pupae from both species are very similar. The eggs are white, microscopic and often have bits of flour stuck to their surface. The slender larvae are creamy yellow to light brown in color. They have two dark pointed projections on the last body segment.

The red and confused flour beetles live in the same environment and compete for the same food sources. The red flour beetle may fly, but the confused flour beetle does not. The red flour beetle is reddish-brown in color, and its antennae end in a three-segmented club. The confused flour beetle is the same color, but its antennae end is gradually club-like – the “club” consisting of four segments.

The red and confused flour beetles may be present in large numbers in infested grain but are unable to attack sound or undamaged grain. These beetles can be found not only inside infested grain products, but in cracks and crevices where grain may have spilled. They are attracted to grain with high moisture content and can cause a grey tint to the grain they are infesting. The beetles give off a displeasing odor, and their presence encourages mold growth in grain.

Saw-toothed grain beetles
The saw-toothed grain beetle adult is a small, active brown beetle, – 1/8-inch long – with a flattened body and six saw-toothed projections on each side of the thorax. The larva is yellowish-white, about two to three mm long, with a brown head. The abdomen tapers toward the tip. The adults are long-lived and have been kept alive for over three years. Under ideal conditions, the life cycle is completed in about 30 days.

The saw-toothed grain beetle is one of the most widespread of all stored-product pests and can originate at the manufacturing, storage or retail levels. They may occur in million-bushel grain bins or may be found in the pantry at your house. Foods that may be infested include cereals, flour, pastas, dried fruits, dried meats, candies and other similar packaged goods.

As with other stored grain product insects, it is the larvae that do most of the damage, yet it is the adult insect that is most commonly encountered. Adults cannot attack sound, solid whole kernels of grain but rather feed on damaged kernels.

If you are interested in receiving a free poster of the “Dirty Dozen” (12 most common stored-product pests), please contact perrynettles@foodprotectionservices.net.

Perry Nettles is the Delta Region Manager for Food Protection Services in Bay, Ark. Contact Nettles at (870) 243-0897 or at the above email address.