Read the full story in Agricultural Research magazine.

The “Fort Knox” of Microbial Weed Whackers

As yellow starthistle and other exotic weeds begin their spring assault on crop fields, rangeland, parks and even backyard gardens, researchers are testing the microbial mettle of fungi, bacteria and other organisms to check the pesky plants' advance.

The approach, called classical biological control, is only one front in America's multi-billion dollar war on exotic weeds like yellow starthistle. In California alone, this invasive species has expanded its range from 1.2 million acres in 1958 to the present 7.9 million acres. Like other such weeds, the thistle thrived after escaping from its homeland’s natural enemies.

More stories about weed biocontrol research:

• Progress against starthistle in the West (Feb. 1999)
• ARS strategies (Mar. 2000)
• Details on several projects (Mar. 2000)

But scientists at the Foreign Disease-Weed Science Research Unit in Frederick, Md., are planning a long-overdue reunion. The facility, which includes three microbial containment greenhouse facilities, is operated by the Agricultural Research Service, the U.S. Department of Agriculture’s chief scientific arm.

Since the 1970s, Frederick researchers have sought to slow the advance of exotic weeds with biological, rather than chemical means. Cost, environmental concerns, and the extent of infestations themselves are three reasons for this approach.

Biocontrol agents that pass muster and safety protocols, like the rust fungus Puccinia carduorum Jacky, also apply constant pressure on invasive weeds that tillage, chemicals and other controls often can’t, notes Bill Bruckart, an ARS plant pathologist.

Unleashed onto a Virginia exotic musk thistle infestation in 1987, the rust fungus has since pursued the weed with dogged persistence, often reducing its host’s populations up to 90 percent, as far west as Wyoming and California.

Charged with determining a foreign weed pathogen’s identity, host range, and biocontrol potential, the ARS lab is first stop in a national campaign that also involves USDA’s Animal and Plant Health Inspection Service, the U.S. Environmental Protection Agency, the Weed Science Society, and state ag departments. You can read more about it in the May issue of Agricultural Research magazine. Click here to read the story on the web.

Scientific contact: William Bruckart, ARS Foreign Disease-Weed Science Research Unit, Frederick, Md., phone (301) 619 7340, fax (301) 619-2880, bruckart@asrr.arsusda.gov.