Grain Moth

The grain moth, best known by its common name the Angoumois grain moth, is one of the most widespread pests of stored cereal grain in the world. Unlike many stored-product moths that feed on grain dust and broken kernels, its larva develops entirely inside a single intact kernel of corn, wheat, rice, or other cereal, making early infestations difficult to detect from the outside.

Adults are small, delicate moths that are weak fliers and tend to stay close to the grain mass where they emerged, though they can disperse into storage facilities and homes. Infestations tend to build up in warm, poorly ventilated grain storage and can spread rapidly under favorable temperature and humidity conditions.

Because the larval feeding is concealed within kernels, damage is often first noticed as small round exit holes in grain or as a buildup of fine kernel dust, along with adult moths fluttering near stored grain containers.

• Forewings narrow, pale buff to yellowish-brown, sometimes with faint darker speckling
• Hindwings pointed at the tip with a distinctive fringe of long hairs
• Wingspan roughly 1/3–1/2 in (8–12 mm)
• Adults hold wings tent-like over the body at rest
• Larva is a small, whitish caterpillar that develops and pupates entirely inside a single grain kernel
• A round exit hole with a thin flap left by the emerging moth is a telltale sign in infested kernels

Found wherever cereal grain is grown, harvested, or stored, including farm bins, commercial silos, mills, and household pantries. It is established nearly worldwide in grain-growing regions, with heaviest activity in warm climates and during warm storage seasons, since development slows considerably in cool temperatures.

Adult females lay eggs on or near grain kernels; newly hatched larvae bore directly into a kernel and feed concealed inside, consuming the starchy interior as they grow. A fully grown larva pupates within the hollowed kernel and the adult moth chews a small round exit hole to emerge. Adults do not feed and live only a short time, focusing on mating and egg-laying near new grain.

Development is complete metamorphosis: egg, several larval instars feeding inside a single kernel, pupa formed within the same kernel, and a short-lived adult moth. Under warm conditions a generation can be completed in about a month, allowing several overlapping generations per year in heated storage, while cooler temperatures slow or halt development.