What can farmers do when two of the world's worst weeds are in cahoots with one of the world's worst roundworm crop pests, reducing yields up to 40 percent in chile peppers and 25 percent in cotton?

The weeds in this case are purple nutsedge and yellow nutsedge and the worm is the southern root-knot nematode. All three share a vast range on five continents, from southern South America, Africa and Australia northward into Asia and the southern portion of the U.S. - including southern New Mexico.

Farmers and researchers have long recognized all three as significant pests, but the symbiotic relationship between the nematode and the two nutsedges did not become apparent until recently. Much of this understanding has come from work done at New Mexico State University by researchers in weed science and nematology.

The key NMSU investigators have been Jill Schroeder, professor and interim department head in NMSU's Department of Entomology, Plant Pathology, and Weed Science; Steve Thomas, also a professor in EPPWS; and research associates Cheryl Fiore and Jacqueline Beacham.

Statistical design has played a significant part in the analysis of the data. Leigh Murray, formerly an NMSU faculty member and now a professor at Kansas State University, is the main collaborator on this facet of the research. Other NMSU collaborators have included Ian Ray, a professor of alfalfa genetics in the Department of Plant and Environmental Sciences, and Jim Libbin, professor of agricultural economics and an associate dean in the College of Agricultural, Consumer and Environmental Sciences.

In southern New Mexico, southern root-knot nematodes infect the roots of chile and cotton plants, just to name two very commercially important plants. The nematodes cause bulges known as galls that interfere with water uptake to the leaves and fruit. According to Thomas, who directs NMSU's nematology lab, the worms also send a chemical signal to their host plants that essentially says, "I'm a fruit," tricking the plants into rerouting photosynthates from the leaves to the roots, thus depriving the chile pods and cotton bolls of nutrients.