Identification breakthrough DNA fingerprinting for suspect beetles

Mr Rob Emery: DNA technology for quick identification of stored grain pests. INSET: Warehouse beetle larvae. Khapra beetle larvae are identical.

Picture this: Researcher gets urgent call at 7.00 pm saying taxi driver en route from Albany to Perth with a vial of beetle larvae to be identified. Driver arrives at midnight, hands over vial and returns to Albany.

Researcher rushes into lab and dissects larvae, searching for telltale identification in places like the roof of the larvae's mouth. Once sure, researcher hops on the blower to quarantine officer in Albany.

At stake: megadollar costs to fumigate a ship's hold for the presence of the dreaded Khapra beetle or the more common warehouse beetle, or the loss of an equal amount for each additional day the ship is in port.

"Up till now. adults and larvae suspected of being warehouse beetles or Khapra beetles could only be reliably identified in WA by my technician or myself," says Agriculture Western Australia entomologist Rob Emery.

Rapid beetle identification

A project funded by growers through the GRDC has changed all that. Mr Emery and co-workers have adapted molecular technology called 'DNA fingerprinting' to identify this group of beetles. The new technology will enhance Australia's ability to export pest-free and chemical-free grain.

Developed at Agriculture Western Australia and the State Agricultural Biotechnology Centre at Murdoch University, the DNA comparison offers quick and accurate identification between pest and non-pest Trogoderma, particularly the Khapra beetle, to avoid unnecessary fumigations of misidentified insects.

"From a farmer's perspective a rapid and accurate identification is equally important to contain any suspicious beetles that may have found their way onto the farm." said Mr Emery.

Khapra or not

Australia has many species of native Trogoderma that are of no economic significance but occasionally find their way into storages. However, two Trogoderma are of economic concern. The warehouse beetle (Trogoderma variabile) is a quarantine-status pest in Australia, and must be controlled whenever detected. It was discovered in eastern Australia in 1978 and, despite eradication and containment programs, has continued to spread.

It is more difficult to control than other stored product pests because of its tendency to colonise cracks and crevices, avoiding pesticide treatments. The larvae also have the ability to survive long periods without food in a nondeveloping state.

However, it is the warehouse beetle's close relationship to the feared Khapra beetle (T. granarium), which is the major concern. The Khapra beetle is considered the most serious pest of stored grain in the world.

"There is the possibility that a warehouse beetle could find its way into a shipment of export grain and be mistakenly identified as a Khapra beetle by an overseas customer. This occurred in the 1950s and it took many years for Australia to remove the stigma of being listed as a Khapra beetle country." said Mr Emery.

Conversely, the presence of warehouse beetle infestations could mask an invasion of Australia by the Khapra beetle.

How 'DNA fingerprinting' works

Mr Emery said his laboratory is now using the DNA technique on quarantine specimens.

It involves the extraction of random fragments of Trogoderma DNA that are amplified and tested to see if they are unique to that species. The likelihood of different species having the same DNA fragments is very low.

The technique is quick and doesn't require a trained entomologist. It can be used on body parts (good results have been obtained using only a leg) of fresh or dead specimens of adults or larvae. Mixed samples of Trogoderma can be processed simultaneously with only one Khapra beetle needed to cause a positive reaction.

Growers who find hairy larvae they suspect of being the warehouse beetle can send their specimens to Mr Emery for identification. (Send to Mr Rob Emery, Agriculture Western Australia, 3 Baron-Hay Court, South Perth, WA 6151).

Subprogram 1.8.1 Contact: Mr Rob Emery 09 368 3247

Region North, South, West