Khapra beetle

Khapra beetle (Trogoderma granarium) is one of the most serious pests of stored grain products, especially under hot and dry conditions.

Khapra beetle is a regulated quarantine pest in many countries and currently absent from Australia. Our international trade would be severely impacted if it became established here.

Khapra beetle will feed on most dried plant or animal matter. It 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. Its preferred grain and cereal products are wheat, barley, oats, rye, maize, rice, flour, malt and noodles.

It also feeds on:

• soybeans, lentils, dry peas, grain sorghums, cowpea and corn
• rolled and ground barley, ground corn, ground dog food, rolled oats, dried orange pulp, ground rice, and cracked and ground wheat bran
• peanuts, pecans, walnuts and almonds.

Other commodities that often serve as hosts include:

• bread, dried coconuts, cornmeal, crackers, white and wholemeal wheat flour, pasta, dry baby food, pearl barley and wheat germ
• rat and mouse baits, snail pellets.

Khapra beetles are small, oval-shaped and densely hairy, reddish-brown beetles.

• 5–3.5 mm long, 1.1–2.0 mm wide
• head and the first third of the body is dark reddish-brown
• wing covers (elytra), reddish- or yellowish-brown, usually with indistinct lighter bands marked by whitish hairs
• venter (underside) of body, reddish-brown
• legs, yellowish-brown
• hairs (setae) on the dorsal surface are of two types: evenly distributed, yellowish-brown; and on the wing covers two or three bands of indistinct yellowish-white
• middle eye (median ocellus) on the front of the head is always distinct
• antennae are yellowish-brown, short, with a distinct club.

  Dorsal diagnostic image of Trogoderma granarium. Photo – © 2013 Pia Scanlon

Newly hatched larva are whitish with yellowish-white hairs, 1.6–1.8 mm long and 0.25–0.3 mm wide. A little more than half of the length comprises a long tail of a number of hairs.

Mature larva are creamy coloured and covered with dense, brownish hair, about 6 mm long and 1.5 mm wide.

Note: Warehouse, carpet and hide beetle larvae are almost identical in appearance to khapra beetle larvae. Only microscopic examination can separate them, so specimens should be sent to the DPIRD for positive identification.

Please see PaDIL (Pests and Diseases Image Library) for high quality diagnostic and overview images.

Go to PaDIL

In storage facilities pheromone trapping and larval traps have proved to be useful surveillance tools. Inspectors should be aware of the potential for inadequately cleaned shipping containers to harbour an infestation, especially in the sub-floor area. Because larvae can survive for years without food, infestations can be found in containers transporting non-food products.

Khapra beetle is of great quarantine concern. Inspection at ports and entry points provides an effective way to restrict entry of this pest. The Diagnostic Protocol for the regulated pest Trogoderma granarium prepared by the European and Mediterranean Plant Protection Organization (EPPO), in English and French recommends means of positive identification and detection of the insect pest.

The protocol also includes description, impacts, host range, geographical distribution. The Pest Risk Assessment of khapra beetle conducted by the United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine (USDA, APHIS, PPQ), addresses the likelihood of the beetle becoming established in the United States, the economic consequences, and available information regarding pathways, probability of detection, and marketing/export consequences of infestation in the US.

Growers should also take preventative measures on farm by keeping an eye out for 'hitchhiker’ pests, such as khapra beetle, to ensure early detection and prevent spread. When opening imported cargo, pallets or packages, follow the below guidelines:

• Vehicles, machinery etc delivered on pallets should be opened on concrete, and in a contained environment, if possible.
• DO NOT open in the paddock or close to crops or storage.
• Check packaging/goods carefully.
• If you find something close the container/package or create a barrier (such as a blanket or tarpaulin), and isolate.
• Take photos, recording the location and collect a specimen if safe to do so. Use a knockdown spray as a last resort. Don’t use a knockdown spray if it will cause the insects to disperse.

Look for small beetles, larvae or cast skins found in cracks and wall linings of storage containers. Report any findings IMMEDIATELY.

In India, the use of deoiled neem (Azadirachta indica) seed powder and diatomaceous earth powder mixed into wheat seemed to be an effective and cheap method to control the pest in stored wheat, though these are not accepted for eradication or quarantine treatment.

Heat treatment has proved very effective. The treatment involves a 30-minute exposure at 60°C which has given a 100% kill of all stages of the beetle. Mortality of larvae begins at 42.5°C. Complete mortality however required eight days exposure at that temperature.

Inactive larvae are more resistant to high temperatures than non-diapausing ones. When heat treatment is used it is imperative that the centre of the stored product should be maintained at the desired temperature for at least half an hour.

Treatment with fast electrons, using a linear accelerator, could provide an efficient method of controlling khapra beetle in store grain.