Improved Fungicides May Be Easier on Environment

MONDAY March 23, 2009 -- A new group of environmentally friendly fungicides may prove to be safer, more selective and less likely to fall victim to pests becoming resistant to them over time, Canadian researchers report.

Called phytoalexin detoxification inhibitors, or paldoxins, the fungicides bolster a plant's natural defenses by blocking access to the chemical pathways that fungi use to weaken a plant's resistance. Unlike conventional fungicides that kill everything -- good and bad -- in their path, paldoxins harm only the disease-causing organisms, said the researchers, who were to present their work Monday in Salt Lake City at the national meeting of the American Chemical Society.

"Our products only attack the fungus when it's misbehaving or attacking the plant. And for that reason, they're much safer," study leader Soledade Pedras, a chemistry professor at the University of Saskatchewan in Canada, said in a news release from the meeting sponsor.

Plants produce natural chemicals called phytoalexins that help them ward off attacking fungi. However, sometimes fungi can become too tough, destroying the phytoalexin and overwhelming the defenseless plant.

In laboratory tests on plants that normally handle fungicides well, Pedras's team found that the phytoalexin in a camelina, a flowering plant also called "false flax," proved to be the most powerful and effective at thwarting the killer enzymes many fungi use to attack plants.

"We found that many fungi couldn't degrade this chemical," Pedras said. "So that's what we used to design synthetic versions that were even stronger than the original."

The team has developed six synthetic versions of the paldoxins, which in lab tests have successfully protected generally fungicide-friendly crucifer plants and vegetables, such as rapeseed plants and mustard greens. Field tests, in which the paldoxins would be applied like regular pesticides, will soon take place on tougher-to-protect grass crops such as wheat, rye and oat, Pedras said.

More information

The U.S. Environmental Protection Agency has more on pesticide safety.

Posted: March 2009


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