Appendix A:Fact Sheet on Principal Stored Grain Insects
FACT SHEET ON PRINCIPAL STORED GRAIN INSECTS
THE INFORMATION OUTLINED BELOW IS REPRINTED WITH PERMISSION, AND ADAPTED FROM PUBLICATION E-80, APRIL, 1967, DEPARTMENT OF ENTOMOLOGY, COOPERATIVE EXTENSION SERVICE, PURDUE UNIVERSITY, LAFAYETTE, INDIANA 47907.
- GRANARY WEEVIL, Sitophilus granarius (Linnaeus). This true weevil, along with the closely related rice weevil, is among the most destructive of all stored grain insects. The larvae develop inside kernels of whole grain in storage, thus making an infestation difficult to remove in the milling process. Therefore, the granary weevil is largely a pest of stored wheat, corn and barley, especially in elevators, mills and bulk storages. The adult cannot fly, and field infestations do not occur.
- SAW-TOOTHED GRAIN BEETLE, Oryzaephilus surinamensis (Linnaeus). Along with flour beetles, the saw-toothed grain beetle is one of the most common insects in stored grain and cereal products. The larvae develop in flour, cereal products and many other dried foods, For this reason, it is a common pest not only in grain bins, but also in elevators, mills, processing plants, warehouses and kitchens. In grain bins, it feeds on broken kernels and grain residues.
- RED FLOUR BEETLE, Tribolium castaneum (Herbst). This beetle is similar to the saw-toothed grain beetle in habits and types of products infested. It is a serious pest in flour mills and wherever cereal products and other dried foods are processed or stored. Like the confused flour beetle (not pictured), the red flour beetle may impart a bad odor that affects the taste of infested products.
- LARGER CABINET BEETLE, Trogoderma inclusum (LeConte). Representing a group also referred to as Trogoderma, the larger cabinet beetle is a scavenger that feeds on cereal products and dried animal matter. The fuzzy, slow-moving larvae - similar to the larvae of carpet, hide and larder beetles - are often found crawling about on or near the products they infest.
- LESSER GRAIN BORER, Rhyzopertha dominica (Fahricius). This pest is most common and destructive in warm climates but can spread to any area in transported grain. It is a problem of grain only and not cereal products. The larvae develop inside the kernels of whole grain. The adults also damage grain by boring into the kernels and leaving them covered with powder from the chewed material.
- RICE WEEVIL, Sitophilus oryzae (Linnaeus). The rice weevil is similar to the granary weevil in both appearance and habits. The name is misleading, however, since it infests other grains besides rice. Adults can fly and, in warm climates, can cause widespread damage to corn, wheat and other grains before harvest.
- INDIAN-MEAL MOTH, Plodia interpunctella (Hubner). Common to both stored grain and cereal products, Indian-meal moth larvae cause damage in corn meal, packaged foods, bagged grain and grain in storage. Attack is confined to surface layers of stored shelled corn and small grains. In the case of stored ear corn, however, feeding occurs anywhere, since the moths crawl among the ears to lay their eggs. Larval feeding is characterized by a webbing of the material infested. The mature larvae then often leave the material and crawl about in homes or buildings in search of a place to pupate.
- CADELLE, Tenebroides mauritanicus (Linnaeus). Both the adult and larva are large and easy to see. Both stages feed mainly on the germ of stored grains, but may also attack milled cereal products. The larvae leave stored grain in the fall and burrow into woodwork, such as wooden bins or boxcars, to hibernate. They may also burrow into packaged cereal products, thus providing an entrance for other cereal pests.
- FLAT GRAIN BEETLE, Cryptolestes pusillus (Schonherr). This is a tiny beetle that feeds primarily on the germ of stored grains, especially wheat. It is readily attracted to high-moisture grain. In fact, under high moisture conditions, the flat grain beetle may also develop in many cereal products, but it is not a common pest in kitchens.
- ANGOUMOIS GRAIN MOTH, Sitotroga cerealella (Olivier). This is a common and destructive pest of crib ear corn. It also infests stored shelled corn and other small grains, but attack is confined to the surface layer of grain. The larvae develop within the kernels; therefore, the Angoumois grain moth is not a pest of cereal products. Infestations in homes often occur in stored popcorn or in colored ears of corn kept for decoration purposes. The moth resembles the clothes moth but does not shun light.
A native of India, the Khapra Beetle has spread to other countries in Asia, Africa, Europe, & North America. While it thrives best in warm climates, there is evidence that the beetle can survive cold winter months in heated warehouses and grain storage tanks. The beetle is a sluggish insect. It cannot fly and is spread entirely by shipping & trade. The problem of preventing the insect's spread is compounded by its ability to survive for several years without food & by its habit of hiding in cracks, crevices, and even behind paint scales. Left uncontrolled, they can make the surface of a grain bin come literally alive with millions of wiggling larvae eating their way down to the bottom.
In addition to the obvious grain and stored product hosts, the beetle turns up in a variety of locations that would not be obvious food sources for the pest. It is often found in the ears & seams of burlap bags & wrappers, in baled crepe rubber, automobiles, steel wire, books, corrugated boxes (glue), bags of bolts, & even soiled linen & priceless oil paintings. It is frequently intercepted on obvious food products such as rice and peanuts as well as dried animal skins. Such infestations result from storage of the products in infested warehouses, by transportation in infested carriers or from re-use of sacks that previously contained products infested by the Khapra Beetle.
Except for some attempts to develop traps and lures for the Khapra Beetle, the only sure inspection is visual. Certainly this is a meticulous chore because of the tiny size of the Khapra Beetle.
High risk areas first checked include:
- cracks in flooring & walls
- behind loose paint
- along pallets
- seams of burlap bags
- any low light areas & dark crevices
- trash from cleaning devices
Low risk areas for inspection include:
- well-lighted areas or areas where sun-light penetrates
- areas which are moist or where debris are covered by mold
Vacuum cleaners are now being used by inspectors to assist the inspection process to draw larvae & cast skins out of cracks & crevices. Filters are changed between inspection locations.
LIFE CYCLE AND DESCRIPTION
The tell-tale signs of a Khapra Beetle infestation are the larvae & their cast skins. The larvae are yellowish or reddish brown. Clothed with long barbed brown hairs, the larva has a tuft of longer hairs which gives it the typical carper beetle larva look. Adults are brown to blackish in color with indistinct red-brown markings on the wing covers. Hairy on top, they may have a slick appearance when hairs are rubbed off. Mature larvae and adult females are about 1/8 inch long; males are somewhat smaller. They pass through 5-9 moults during this stage, resulting in numerous cast skins. Adults are short-lived, persisting for a few days at temperatures over 100°F, or for perhaps several months or even years, at temperatures below 50°F. Adult activity is little noticed except at dusk, while remnants are seldom found as they are cleaned up by larvae. Mating occurs almost immediately following adult emergence, and egg deposition follows in from 1 to 6 days. Eggs are laid loosely among the host material infested. Hatching follows from 1 week to 2 weeks after deposition. Two types of larvae, short or long cycle, may develop. Under optimum conditions, the larval stage may be completed in less than a month, whereas under crowded, starving or cold conditions, long cycle larvae may hide out in large numbers in building crevices and may persist from several months to 3 years without food.
Fumigationusing methyl bromide is the treatment of choice. Because the pest secrets itself in cracks & crevices of the building it is in, in addition to the contents, the whole building must be treated. Typically, the building is covered tightly with tarpaulins and fumigant is pumped in at the approved rate of 6 to 9 pounds per 1,000 cu. ft. The process takes several hours depending on the size of the building, and strict safety precautions are taken.
- Last Khapra Beetle significant incident: 1978, single infested warehouse in Linden, NJ.
- Last infestation found and eradicated: 1966.
- Domestic quarantine revoked: September 2, 1972
- Original find in U.S.: grain warehouse at Alpaugh, CA, November, 1973.
- Infestations subsequently found and eradicated in Arizona, California, New Mexico, Texas, & Mexico.
- Report suspected Khapra beetle infestations to State or Federal plant pest control inspectors. Collect samples in vials of alcohol. Submit samples of unsuspected Khapra Beetles to your District lab or mail to:
U.S. Department of Agriculture
Plant Protection& Quarantine Program
Hyattsville, Maryland 20782
LIFE CYCLES OF SELECTED STORAGE INSECTS
*These figures are approximate, and depend on food and environmental factors.
|Insect||Number Eggs laid by female||Length of egg stage (days)||Length larval or nymphal stage (days)||Days of Total Development||Length of Adult Life|
|Flat grain||100-400||3-4||20-80||40-90||1-12 months|
|Tribolium||350-400||4-12||20-100||30-120||to 3 years|
|20-285||3-5||14-50||20-70||6 months to 3 years|
|Indian Meal||100-300||3-4||21-120||45-150||2-25 days|
|Cockroaches||100-1000||35-100||30-500||65-600||up to 2.5 years|