Originally created 06/19/03

Scientists test radio waves to kill bugs in nuts



PARLIER, Calif. -- Dried fruit and nut packers looking for an alternative to harmful insecticides might soon be able to kill pests in storage bins with the flip of a switch.

Researchers are testing radio waves - electromagnetic waves that can make molecules vibrate and heat up in the same way that microwaves heat food - and their ability to kill pests without harming product quality.

Scientists hope the method, which is already used to dry cereal, crackers, clothing and plywood, can be used as an alternative to chemical treatments.

Nut packing houses commonly use methyl bromide, phosphate or other fumigates to kill nut pests like codling and Indianmeal moths. Packers typically spray the nuts in a large room and leave the chemical on for three days before the nuts - with dead bugs inside - are shipped off.

"If they didn't treat it, the bugs would reproduce, and you would have moths flying around. You're trying to prevent the problem becoming bigger and more of the product being damaged," Mitcham said.

The federal government will ban methyl bromide in 2006 because it breaks down the ozone layer and has been linked to birth defects and neurological damage.

In test runs at UC Davis, small batches of walnuts, pistachios and other nuts are placed in a slightly salty liquid solution and then put in a radio frequency unit - a machine that looks like a huge microwave oven. The unit "cooks" and kills the worms without overheating the nut.

"There has been improvement in technology and it's become less expensive. Now people feel it's a viable option," said Elizabeth Mitcham, a fruit specialist at UC Davis.

While many test runs have been successful, scientists say the method may be more expensive than chemicals because electricity is used. Researchers also are trying to devise a radio frequency machine that would allow nuts to be treated as they are quickly run through a conveyor belt.

Industrial-size radio frequency machines will be tested at a large packing house in January and could be available for commercial use by fall 2004.