Anti-insect ozone.

In attempts to control insects and the diseases they bring, farmers have relied on variety of pesticides, many of which are highly toxic to humans. Meanwhile, insect resistance is growing. Replacement technologies are critical. Now associate entomology professor Linda Mason and colleagues at Purdue University are investigating ozone as one possible replacement.

According to the U.S. Department of Agriculture, insect damage to the nation's stored wheat crop costs some $500 million annually; Purdue's agriculture department estimates that about 5-10% of the world's food production is lost during storage each year because of insects, with some countries losing as much as 50%. Insects such as the lesser grain borer, the red flour beetle, and the rusty grain beetle not only devour vast amounts of stored grain, but add insult to injury by defecating on the kernels, triggering the growth of fungi and molds such as Fusarium and Aspergillus. Fusarium infection can cause illnesses from esophageal cancer to alimentary toxic aleukia, and the aflatoxins produced by Aspergillus can cause cancer and damage the brain, liver, and kidneys.

Ozone has been used to purify water, and the agricultural industry has used it to decontaminate perishable foods and disinfect manufacturing equipment, water, and packaging materials. Neither the volume nor the concentration used are high enough to contribute to environmental problems. The only breakdown product of ozone is oxygen.

Mason and colleagues filled three containers with wheat, then applied ozone at a concentration of 50 parts per million for 30 days. The result was 92-100% mortality of a number of typical grain pests as well as fungi on the kernel surface. The study also showed that current commercial aeration systems used in grain storage are adequate to distribute the ozone freely throughout he grain mass. Subsequent studies showed similar results for other grains such as maize, popcorn, rice, and soybeans, with no degradation of flavor or nutritional value. This research was published last year in the Journal of Stored Products Research.

Dennis Avery, director of the research group Center for Global Food Issues, says that, while any environmentally benign approach to protecting grain is welcome, there are some potential issues. "The problem with any sort of gaseous fumigation is that storage facilities in countries that really need the protection are not designed to hold in the ozone," he says (a charge Mason counters by noting that the system does not require airtight storage). "That being said," Avery adds, "I think anything that allows us to keep insects from infesting grain with minimal risk to humans and a lower risk of pesticide resistance is very much to be welcomed."