 ethyl bromide, the second most
widely applied insecticide in the world, will be phased out over the next
three years because of ozone depletion. Iowa State University professor
Joel Coats and some of his students and colleagues are developing alternative,
environmentally friendly pesticides that might help replace methyl bromide.
 Coats, an entomologist and toxicologist,
is studying two natural compounds from flax and cassava plants acetone cyanohydrin
and methylethylketone cyanohydrin. Research shows the compounds kill several
common and costly insect pests that feed on crops and stored grain in the
United States. These insects include the maize weevil, the lesser grain
borer, the red flower beetle, the drug store beetle and the saw-toothed
grain beetle.
Coats and Greg Tylka, associate professor
of plant pathology, have also found the natural pesticides destroy the eggs
of the soybean cyst nematode, a costly pest that invades Midwest soybean
fields.
Coats believes the natural compounds
work as respiratory inhibitors in insects. The compounds are fumigants,
vapor-borne insecticides of small, volatile molecules that can evaporate
and penetrate to kill pests and their eggs. They are just as effective as
the commercial insecticides but are biodegradable since they don't contain
bromine or chlorine.
"Natural is the wave of the
future," Coats said. "There will be a slow, sure change to natural
insecticides."
Coats began looking for natural insecticidal
compounds five years ago. Although the natural insecticides will probably
be more costly than methyl bromide, they will be a viable alternative when
methyl bromide is no longer legal, he said.
"The whole direction of insect
control is going to have to go toward more specialized chemicals to use
on specific pests as opposed to use of just a few broad-spectrum pesticides,"
Coats said.
The Iowa State University Research
Foundation has a patent application pending for fumigants derived from natural
resources based on Coats' work.  | 
iastate.edu.