Khapra beetle (Trogoderma granarium)

Type of pest: Primary pest, secondary pest.

Distribution: North and West Africa to Burma and Central Asia. Occasional or absent in Europe; North, North East and South East Asia; Southern Africa; absent in Australia and the Americas. The khapra beetle is thought to have originated in India.

Identification: Adults are 2 – 3.5 mm, oval, hairy, with elytra unmarked or light markings. The antennal club has three to eight segments, joined symmetrically. Larvae: eruciform, oval, with bands of hairs as Trogoderma variabile.

Similar species: Anthrenus, Anthrenocerus, other Trogoderma – identification is only reliable by examination of genitalia and internal structures.

Life cycle: The life cycle is complete in 26 to 220 days depending on temperatures. Khapra beetle populations can increase rapidly under optimal conditions (hot and dry). Optimal conditions are 25 days at 33-37 ºC, 45-75% r.h. In adverse conditions this insect can enter larval diapause and survive in this state with limited food for several years. Eggs are laid amongst the commodity. Larvae are mobile, cast skins left in infested material, surviving without food for years. Adults are short-lived, do not feed on the commodity and do not fly.

Commodities infested: The Khapra beetle will feed on most dried plant or animal matter. However they prefer grain and cereal products, particularly wheat, barley, oats, rye, maize, rice, flour, malt, and noodles. They can feed on products with as little as 2% moisture content and can develop on animal matter such as dead mice, dried blood, and dried insects. Damage by this insect is mostly caused when the larvae feed. Signs of infestation are cast larval skins in and around infested foodstuffs and dust-like debris. If the beetle is left undisturbed in stored grain it can cause significant weight loss, and in the case of seeds, it may lead to significant reduction in seed viability. Infestations are difficult to control because of the insect’s ability to survive without food for long periods. Severe infestation may cause unfavorable changes in chemical composition.

This beetle has never been observed to fly; therefore its spread is probably dependent on movement of infested goods or in containers where it may be transported while in diapause. The Khapra beetle is a quarantine pest in many countries and is more resistant to fumigants than most stored product pests.

Treatment: Controlled Atmosphere for infestation in product
Treatment: Heat Treatment for infestation in buildings