When federal land managers spread herbicide on rangelands 15 miles from Malaga, N.M., in mid-July, they had no idea what a mess they were making. A week later, a flash flood washed Spike 20P pellets into the Black River, contaminating a diversion ditch.


"Supposedly, in moderate rain, the pellets would dissolve into the soil rather than wash into the stream," says Tom Davis of the Carlsbad Irrigation District, noting that Spike 20P's label encourages users to apply before "sufficient rainfall." "But this was like a high-pressure hose on a parking lot."


Ten days later, half a dozen farmers noticed that their cotton plants, alfalfa fields, pecan trees and even cottonwood stands were dying. A private firm hired by the farmers discovered the chemical tebuthiuron - the active ingredient in Spike 20P - in plant tissue from the farms.


But the Bureau of Land Management suggests that other sources may have contributed to the contamination. "In the area where we applied the tebuthiuron, the vegetation is being affected," says Mary Jo Rugwell with the BLM Carlsbad field office, "so, obviously, it didn't all wash away."


Tebuthiuron concentration in the ditch has significantly decreased since July, but fields irrigated with the tainted water may need to lay fallow for several years. Davis knows of no other Spike 20P users in the area, and believes the farmers should have been consulted before the application. Eleven farmers are planning to sue the federal agencies and Dow Agro, the manufacturer of Spike 20P, and Sen. Jeff Bingaman, D-N.M., has drafted legislation to compensate the farmers.