May 2, 2005

US soybean crops threatened by choking vine

The US state of Indiana, with a booming soybean industry, is now threatened by Kudzu, a fast-growing green vine that has spread to at least 28 counties.

Kudzu was first planted in the United States in the 1930s to control soil erosion. It now covers millions of acres in the south, where it threatens woodlands. Worse, strands of the vine in Florida were found to harbour the deadly rust fungus that preys on soybean plants, according to Purdue University.

Soybean rust has not yet been found in Indiana, but plant pathologists believe it is only a matter of time before the fungus shows up. The rust destroyed soybean crops in South America three years ago and reached US farms late last year.

Kudzu's early leafing vines provide an early target for the wind-borne fungus spores to infect before spreading to soybeans later in the season, explained weed scientist Glenn Nice of Purdue.