The Angoumois Grain Moth (Sitotroga cerealella) is a highly destructive primary pest of stored grains, particularly corn, wheat, oats, and rice. It is named after the French province of Angoumois, where its devastating effect on grain stores was first documented. Unlike many pests that feed on processed grain, this moth is unique because its larva feeds and develops entirely **inside the kernel** of whole grain, making it difficult to detect and control.
Taxonomy and Classification
The Angoumois Grain Moth belongs to the family Gelechiidae, a large family of moths often referred to as twirler moths, in the order Lepidoptera. Its scientific name is Sitotroga cerealella. It is classified as a “primary” stored grain pest because it is able to infest whole, undamaged kernels, unlike secondary pests that only feed on broken grains or dust.
Physical Description
Adult Angoumois Grain Moths are small, delicate moths, measuring about 10–15 millimeters across the wingspan. They are typically straw-colored, yellowish-white, or buff with a distinct satiny sheen. The hindwings are narrow, pointed, and fringed with long hairs. When resting, the wings are often folded tightly over the back.
The larvae are small, creamy white caterpillars with brown heads, growing up to 6 millimeters long. Since they develop inside the grain kernel, they are rarely seen until they emerge as adults. The most definitive sign of infestation is the small, perfectly round **exit hole** (pinhole size) chewed through the side of the kernel when the adult moth emerges.
Distribution and Habitat
The Angoumois Grain Moth is a cosmopolitan pest found wherever cereal grains are grown and stored, especially in warmer climates. It infests grain both in the field (especially corn) and in storage facilities, including grain elevators, farm storage bins, feed mills, and residential pantries. It is particularly attracted to grain stored in the ear or on the cob.
Indoors, infestations are common in shallow bins or sacks of grain where adults can easily access the kernels to lay eggs. They are often seen flying or crawling near windows, having emerged from infested grain nearby.
Behavior and Life Cycle
The moth has a rapid life cycle, completing several generations per year under favorable warm conditions. The female moth lays eggs on or near the grain kernel. Upon hatching, the larva bores into the kernel, seals the entrance, and feeds entirely within the seed coat, consuming the endosperm. Before pupating, the larva chews a tunnel almost to the surface, leaving only a thin cap of seed coat intact.
The adult moth then pushes through this cap to emerge, leaving the characteristic pinhole. Adults are weak fliers and short-lived, focusing primarily on mating and egg-laying. The entire cycle can be completed in as little as five weeks.
Feeding and Damage
The primary damage is the destruction of the grain kernel’s interior by the feeding larva, which severely reduces the grain’s weight, nutritional value, and viability for planting. The presence of the moths and their frass (excrement) also leads to the contamination of stored food, making it unsuitable for human or animal consumption and causing musty odors. Unlike pantry pests that feed superficially, the internal feeding of this moth can go unnoticed until a large number of adults suddenly emerge.
Management and Prevention
Control of Angoumois Grain Moths is achieved through sanitation and proper storage. Grain should be cleaned and dried thoroughly before storage. Airtight storage in large bins is crucial, and if infestation is suspected, the grain can be treated by heating it to $130^{\circ}\text{F}$ for several hours or freezing it for several days to kill all life stages.
In large commercial settings, control involves residual insecticide applications to storage surfaces and sometimes the use of fumigants (if required by regulation and necessity). The use of pheromone traps helps monitor adult populations but is not a control method itself.
Conservation and Research
The Angoumois Grain Moth is a highly destructive economic pest. Research focuses on developing grain varieties with seed coats more resistant to larval penetration, and on testing new, low-toxicity inert dusts (like diatomaceous earth) that can be mixed with stored grain to physically kill the moths as they try to lay eggs or emerge.