Natural Plant Extracts Could Be Methyl Bromide Substitute

A chemical in peaches could become an alternative to methyl bromide for controlling certain soil-dwelling pathogens. Methyl bromide, a chemical now used worldwide on more than 100 crops, has been linked to ozone depletion and will be banned in the United States in 2005. Methyl bromide is critical to agriculture as a soil fumigant, a postharvest storage treatment, and a quarantine treatment to control many pests on various crops.

In preliminary studies, Agricultural Research Service scientists are studying natural plant chemicals as alternatives. One that looks promising is benzaldehyde. Found in peaches and other fruit, benzaldehyde is a naturally occurring colorless, nontoxic, aromatic liquid used in perfumes, flavorings, pharmaceuticals and dyes.

ARS plant pathologist Charles Wilson at the ARS Appalachian Fruit Research Station in Kearneysville, W.Va., found that benzaldehyde controls several soil pathogens, including Fusarium oxysporum, Rhizoctonia solani, Pythium aphanidermatum and Sclerotinia minor. Wilson is working with Debra Fravel of the ARS Biocontrol of Plant Diseases Laboratory, Beltsville, Md. ARS is USDA’s chief scientific research agency.

Benzaldehyde is inexpensive and breaks down into products that aren’t harmful to humans, animals or the environment. Wilson and colleagues found that soil fumigated with benzaldehyde initially had significantly lower pH values. But within two weeks, the pH returned to nonfumigated levels. This showed that changes in soil pH are readily reversed and shouldn’t interfere with crop production.

The scientists have applied for a patent on a time-release formula of benzaldehyde to fumigate fruit, grain and soil. Wilson and collaborators from the Volcani Center in Bet Dagan, Israel and the Fruit, Vine and Wine Research Institute, Agricultural Research Council, Stellenbosch, South Africa, have also found a number of other compounds that are effective against soilborne pathogens.

A story on this research is featured in the March 1999 Agricultural Research magazine. It can be accessed on the Internet at:

http://www.ars.usda.gov/is/AR/archive/mar99/meth0399.htm

Scientific contact: Charles A. Wilson, ARS Appalachian Fruit Research Station, Kearneysville, W.Va.; phone (304) 725-3451, X330; fax (304) 728-2340; [email protected].