Colorado State University recently clinched a $1.8 million grant from the Department of Defense to help battle a new war: the war against weeds that release chemicals that kill other plants. The grant will fund research to identify and isolate chemicals that some invasive weeds are known to release to gain footing over native plants and research the use of those chemicals as natural herbicides, while identifying plants that are resistant to those chemicals. The grant also will be used to develop strategies to revegetate areas heavily populated by weeds.

The grant, given to professors in horticulture, rangeland ecology and weed sciences, will focus on battling weeds in the West, where non-native plants occupy more than 10.5 million acres. Jorge Vivanco, Department of Horticulture and Landscape Architecture; Mark Paschke, Department of Natural Resources; Scott Nissen, Department of Bioagricultural Sciences and Pest Management; and Ragan Callaway, a plant invasion ecology expert from the University of Montana, will partner on the project that also will call on the expertise of other collaborators at Colorado State, state government and private experts.

"We know that some non-native plants - or weeds - successfully use chemicals to invade areas, and we've discovered what a few of these chemicals are," said Vivanco, the project leader. "If we can continue to find, isolate and study these chemicals, we can actually put them to good use as a tool to reclaim some of these weedy areas with native plants. Military bases provide an ideal location to test these ideas in a real setting because they comprise large open areas that are subjected to invasive plants."

Two years ago, Vivanco and fellow researchers discovered and isolated a chemical called catechin that is released through the roots of spotted knapweed, one of the most tenacious of invasive plants in the West. The plant releases catechin through roots and kills surrounding plants. Spotted knapweed itself is protected from the chemical because it is resistant.

The discovery confirmed more than 100 years of speculation that such a chemical existed and opened the possibility of the use of such a chemical as a natural herbicide. The chemical the spotted knapweed produces and releases, and other chemicals like it, called allelochemicals, could be used to control invasive plants.

Alternatively, the group believes some plants that are native to the West may be resistant to allelochemicals and therefore are excellent choices for revegetation of areas now taken over by invasive weeds. Catechin released by spotted knapweed actually exists in soils invaded by the weed at levels twice as high in North America than it does in Europe, where spotted knapweed is a native plant. In a lab, when catechin was placed in the soil, it prevented North American native plant seeds from germinating. However, in some cases, when native plants do survive, their offspring show resistance to catechin.

The group will work on a theory that building a stronger natural habitat for native plants while increasing their resistance to chemicals such as catechin can reduce the number of invasive weeds in a given area.

A multiple approach of their project consists of identifying problem weeds at military bases, identifying additional chemical weapons such as catechin that invasive plants may use to conquer territory and developing its use as a natural herbicide in a real setting by testing it at military training bases. The group also hopes to find plants native to the West that are resistant to the chemical and study ways to detoxify soil from allelochemicals and use that knowledge to revegetate infested areas at military bases.

"We're looking for innovative approaches to recover areas infested with weeds," said Paschke. "It's also important to investigate cost-effective methods to recover large areas. The combination of this research also allows us to try natural methods for recovery."

The grant is given by the Department of Defense because the military is charged with maintaining natural resources, such as native vegetation, on military bases. Because of the large size of bases and the nature of their use, invasive weeds are often an issue.