This beetle was first found in Western Australia in 1989 and that infestation was eradicated. It has spread to about a dozen locations but has never established to damaging populations.
The warehouse beetle larva stage does the damage, attacking a wide range of products. All sorts of cereals, vegetable and flour seeds, notably sunflower seed, paddy rice remnants, carrot and tomato seed, and fish food may be infested. The insect thrives on cereal products such as processed animal feeds or rolled barley and oats, and recently proved to be especially fond of stored canola.
Warehouse beetle can infest a great variety of grocery commodities and seeds. Packaging materials such as second-hand grain sacks and corrugated cardboard can also harbour the pest. The larva can chew through plastic wrappers, aluminium foil, airtight plastic containers and the like.
The larvae of the warehouse beetle are 5-8mm long and covered with thick reddish-brown setae, which gives them a hairy appearance.
The adult beetle is about 3-5mm long, with three indistinct, whitish bands across the wing covers. Dead insects may be greyer in colour. The adult does little damage and will not be as obvious as the larvae because of its short life span of 7 to 10 days.
Larvae and adults of common insects of the same family appear similar to warehouse beetle. Identification requires microscopic examination, so specimens should be sent to the Department of Agriculture and Food for positive identification.
Insects that might be confused with warehouse beetle include carpet and hide beetles, the harmless native Trogoderma or khapra beetle, the world's worst pest of stored grain. Khapra beetle currently does not occur anywhere in Australia and would have a severe impact on international trade if it became established.
Householders are urged to check for the larvae in undisturbed secluded areas, as they are notorious for hiding in the darkest corners and crevices, especially in pantries and drawers. Because the larvae moult many times during development, which can take as long as four years, the large number of cast skins reveals infestations.
To find warehouse beetle larvae:
- Plan a systematic search that leads from one room to another in sequence.
- Look on windowsills, checking all dead beetles, moths, flies etc. as warehouse beetle may be found feeding on these. Lift up the edges of carpets to check for dead adults or live larvae.
- Pull filing cabinets, cupboards, cardboard boxes, packages etc. aside and examine them.
- Check the bottom of shelves, inside drawers, under stoves and refrigerators.
- Check rat and mouse baits or dead carcases, mud dauber wasp and bird nests as well as spiders webs/egg masses.
- Check anywhere warm and dusty. Inspect all foodstuffs and seed in the pantry or food storage area.
- Forward suspect insects to the Department of Agriculture and Food, Western Australia.
Warehouse beetle can only be eradicated using total fumigation techniques, which can only be applied by licensed fumigators. Eradication is made difficult because of the secretive nature and the ability of the larvae to diapause (hibernate) for several years.
Control of the insect around the home can be achieved using a combination of good household hygiene and timely application of recommended insecticides.
Prior to the use of any insecticide or fumigant, a thorough clean–up of the premises is essential to remove harbourage and host material. Thoroughly vacuum the infested area including all cracks, crevices, windowsills, drawers and cupboards. Dispose of debris and vacuum cleaner bag by burning. All infested foodstuffs and produce together with all corrugated cardboard boxes should be burned. Regularly check and dispose of rat baits.
The timely application of both contact and residual insecticides will be necessary to achieve good control of warehouse beetle.
Select one of the registered contact insecticides to kill all active insects and then apply one of the registered residual insecticides to give further protection.
Note that follow-up treatments will be required at six to eight week intervals.
Residual insecticides should be applied to cracks, crevices, windowsills, under furniture and equipment, floors, walls and shelves.
Where major infestations are found in food stores and in stored grain facilities, complete fumigation and stringent hygiene are required.