February 27, 2003
By Rick Callahan
Source: Associated Press
INDIANAPOLIS -- Purdue University scientists have discovered that ozone gas can kill insect pests in grain bins without damaging the grain or causing the environmental harm linked to chemical fumigants.
But the process won't add to the ground-level ozone that is a component of smog, they said.
The finding could lead to portable, ozone-generating equipment that grain elevator operators or farmers could rent to rid their storage bins of insects, the researchers said.
Such a development could be part of an environmentally friendly approach to controlling insects that devour an estimated 5 percent to 10 percent of global food production each year.
The Purdue researchers have been studying the potential of using ozone gas to control insects since 1994.
In a paper published in January's issue of the Journal of Stored Products Research, they report successfully using ozone to treat rice, popcorn, soft red winter wheat, hard red winter wheat, soybeans and corn.
"We found that, yes, you can move ozone successfully through a grain bin, kill insects and there is no damage to the grain. Now, it's a question of scaling it up to be commercially marketable," said Dirk Maier, a Purdue agricultural and biological engineering professor at the school's West Lafayette campus.
Linda Mason, a Purdue entomology associate professor and co-author of the study, said ozone gas killed all of the adult insects it was tested against - the maize weevil, rice weevil, red flower beetle, Indian meal moth and lesser grain borer.
But the gas was ineffective against immature weevils, which develop within grain kernels. Mason said unlike chemical fumigants, ozone does not penetrate deep enough into kernels to kill young weevils.
It isn't clear how the ozone kills the insects, but Mason said the bugs may inhale the gas, which then could act like a neurotoxin.
She began studying ozone's insecticide potential after hearing anecdotal evidence that vents connected to hospital surgical wards where ozone gas was used to kill airborne bacteria were free of cockroaches.
Mason and her colleagues devised a two-phase process for killing the insects with two separate waves of the gas.
The Purdue team is now trying to devise a way to use ozone gas as a vaporous barrier within silos to prevent insects from gaining a foothold.
Ironically, the work that led to Purdue's ozone gas discovery arose from a push for alternatives to potent insect fumigants that contribute to the depletion of the Earth's ozone layer.
Starting in 2005, one such chemical, methyl bromide, will be banned in the United States as part of a 1989 treaty signed by 165 nations aimed at reducing levels of ozone-damaging chemicals. Ozone in the upper atmosphere protects life on earth by absorbing short wave length ultraviolet radiation.
Maier said Purdue's ozone insecticide process uses such low concentrations of ozone that it rapidly dissipates. It would not add to ground-level ozone, which is a component of smog, he said.
Despite Purdue's success, ozone gas will never be a substitute for methyl bromide - it simply isn't as effective as that chemical. But Mason said it could be paired with other techniques to be nearly as efficient.
Maier said a half-dozen companies have contacted Purdue to express interest in the idea. The school may file patent protections on its process.
A $150,000 grant from the U.S. Department of Agriculture's National Research Initiative financed the Purdue team's latest wave of research.