For ranchers in eastern New Mexico and West Texas having broom snakeweed problems, now is the most cost-effective time to control it, says Dow-Elanco range and pasture specialist Bob Capps.

New research from New Mexico State University indicates that spraying snakeweed early in the season — at peak-to-late bloom — can help reduce the seed source and aid long-term control. Typically, peak-to-late-bloom is from mid-September to mid-October.

While the herbicide has little direct effect on seed, spraying at that time does tend to affect the adult snakeweed plant so its seeds don’t mature and become viable. That results in fewer seeds in the soil to germinate after spraying, so the benefits of spraying last longer, Capps explains.

Traditionally, snakeweed spray season has run from bloom through early December, and again in the spring. Spraying after bloom will still control the plants, but seed from those plants may be able to germinate. NMSU research data indicates that most snakeweed seeds in the soil lose their viability after a year, so the first year after spraying is the most critical in preventing a re-invasion.

Broom snakeweed, Capps notes, tends to increase after drouth. He encourages producers to get a handle on the problem before it gets out of hand.

"The best time to control snakeweed," he says, "is not early in the season, but early in infestation."

The standard snakeweed control is picloram herbicide. For broadcast applications in the fall, the recommendation is one to two pints of picloram per acre. For spot treatments, a solution of one-half percent picloram is recommended (two quarts per 100 gallons of water). Users should consult the product label for more mixing and application details, Capps says.