When Richard Snyder's great-grandfather, a pioneer trail driver, helped cut a trail through the West with the legendary John Chisum and Charles Goodnight, chances are that stragglers from the herd got hold of some plants that made them a little "loco." More than a century later, New Mexico cattle ranchers still struggle to control locoweed.

On a pasture near Roy, Snyder slows his truck and looks to the west. "I don't like to see cattle like those three-looks like they're all grazing in one spot," he says. "Sometimes cattle are eating loco. If one animal finds a plant, three or four more will run to it."

Dealing with locoweed has been a lifelong battle for Snyder, who runs the Cedar Creek Cattle Company in Grenville with his wife, Connie. This year, the weeds were worse than ever.

"I have had some bad experiences with it. I've been fortunate to work through it, and I've been lucky enough to survive," he says.

Poisonous plants like locoweed cost livestock producers in Western states more than $330 million each year. In New Mexico's Union and Colfax counties, locoweed accounts for an annual economic loss of more than $5 million, says David Graham, Union County agricultural agent with NMSU's Cooperative Extension Service.

By August this year, Graham had received about 1,000 calls from ranchers throughout the state with locoweed problems.

"Old-timers can tell you that it's been a bad problem for forever, but it seems to be more of a problem now," Graham says. "We don't know if that's something new, or if we're on a 100-year cycle."

The first account of locoweed problems was published in 1873 by the U.S. commissioner of agriculture, says Chris Allison, Extension range management specialist. Since then, researchers have sought ways to prevent poisoning and the side effects of the condition.

Sometimes referred to as milkvetches, locoweeds are members of the pea family. More than 392 species of Astragalus and 22 species of Oxytropis can be found worldwide, Allison says. About 80 grow in New Mexico. Fewer than 20 are poisonous to livestock.

The two major species that cause trouble in New Mexico are white locoweed and woolly (purple) loco, he says.

Poisonous locoweeds contain a compound called swainsonine that affects animal growth, reproduction and the nervous system, Allison says. There's no treatment for livestock poisoned by swainsonine-containing plants.

Animals that eat locoweed may run in circles, stagger or drool. "Usually the first thing you notice is an unthrifty condition," Graham says. "Cattle have a dazed, dull look in their eyes. They start losing weight."

Livestock that eat too much locoweed can eventually starve to death or become so weak that they're easy prey for predators like coyotes, he says. They become more susceptible to respiratory diseases and heart conditions.

Locoweeds are rampant on the 14,000 acres that Snyder leases in Union and Harding counties. A Guide to the Common Locoweeds and Milkvetches of New Mexico, published by NMSU's College of Agriculture and Home Economics, helped Snyder pinpoint poisonous plants in one particular pasture. "I identified eight species of Astragalus here, and half of those were poisonous," he says.

For two months, Snyder checked his cattle every day, gathered the ones that were eating locoweed and put them in a loco-free pasture. "We finally had to ship the cattle to the feed yard," he says. "We're going to lose a ton of money on them."

Ranchers end up with livestock that suffer from weight loss. "The cattle are no good, because they look so bad that nobody will pay anything for them. So they don't sell well at the market price," Graham says.

"So many things can cause cattle to eat loco that it's mind-boggling," Snyder says. "If a cow with a nursing calf eats locoweed, it's harder on the calf. If pregnant cows eat loco, they may abort their calves, or calves may be born with deformities like three eyes. I had a calf born this year with three legs. I don't know if loco caused the deformity, but it sure could have."

Warm winters like last year's provide the right conditions for locoweed to thrive all season, Graham says. It's a cool-season plant that grows in winter.

In the summer, dry plants can remain toxic, but the most dangerous time is between February and April, he says. Locoweeds usually are the first plants to green up during the spring, offering an irresistible meal for livestock.

"The damage to animals is irreversible so you can't accomplish much with any kind of therapy," Allison says. "There is no drug or shot that you can give cattle to get them over locoweed poisoning."

Researchers at the U.S. Department of Agriculture, NMSU and other universities are working on the problem. Studies vary from chemical and biological control to management programs that would minimize locoism in herds, Allison says.

"Scientists are working on microbial populations inside the animal to see if they can develop some microbe that would detoxify the poison," Allison says. "Other researchers are looking at the immune system."

When the toxin, swainsonine, enters an animal's bloodstream, it interferes with protein metabolism. At NMSU's Clayton Livestock Research Center, calves were fed 5, 10 and 20 percent locoweed in their diets and compared to a control group that did not receive any locoweed, says Glenn Duff, the center's superintendent. Animals were then tested for differences in protein patterns in their blood.

"We know that swainsonine completely clears the animal's tissue in about 28 days, but we've never looked at how different levels of consumption affect performance and how long it takes animals to recover from locoweed," he says. "Right now, calves in the feedlot that previously ate 20-percent locoweed diets are gaining about half the weight of calves that did not eat locoweed."

Ranchers who spray locoweed while it's still young have a fighting chance of killing it, especially white locoweed, Graham says. Because woolly loco is more prevalent, it's tougher to control. Ranchers can manage around it by moving cattle to loco-free areas.

But a tenacious insect may come to the rescue. Cleonidius trivittatus, a root-feeding weevil, has been found in higher numbers this year throughout the state. Some ranchers have known about the native bug for many years.

"It only takes a couple of weevils to kill a plant," says Dave Thompson, entomologist with NMSU's Agricultural Experiment Station. "The larvae feed on the inside and outside of locoweeds and cut off the roots. These beetle grubs can take out populations of woolly loco, but they don't attack white loco."

A caterpillar, Walshia miscolorella, invades both white and woolly loco, but rarely kills the plants unless they are stressed in some other way such as from drought, Thompson says.

"Right now, the drought is the best thing that ever happened, because all the woolly loco dried up and died," Graham says. "The weevil also helped. The white loco turned dry, but some cattle still ate it, because it was the most succulent plant in the pasture. The seed pods had more moisture in them than the grass."

As Snyder inspects plants that were treated with a herbicide, he says, "These seeds can live up to 50 years. We sprayed an area here five or six years ago and the loco stayed gone. Now it's coming back. But you can't afford to spray all of the locoweed because it's very expensive."

Even though 1998 has been Snyder's worst year for locoweed, there's a glimmer of hope. In an area that was sprayed this year, all of the locoweed is dead. He also finds evidence left by weevils that have killed many of the plants.

"Hopefully, the combination of dry weather, the weevil and spraying will render this year's seed supply infertile," Snyder says. "There's a chance further down the road that locoweed will become less of a problem."