Noble Foundation soil and crops specialist Eddie Funderburg cites the top seven reasons pasture weed-control programs don't work as well as they should. Spraying too early. Rather than spray on a predetermined date each year, scout the fields and spray the weeds at the proper time based on stage of growth of the weed.
Misidentifying the weed. Scout the fields and learn to identify the weeds in them. After you've properly identified the weed, look at herbicide labels and find one that controls it.
Bad environmental conditions. On virtually all weeds, control declines precipitously when they're in drought stress, Funderburg says. In droughty conditions, for example, if weeds aren't actively growing, they're not taking up the herbicide. In addition to soil moisture, pay attention to wind speed and direction to control off-target drift.
Spraying at the wrong growth stage. Most weeds are best controlled when young and actively growing. Read the label carefully to determine timings for specific weeds.
Using the wrong product. While "the cheapest herbicide" will work on weeds in the easy-to-control category, when conditions are ideal for control, more expensive chemicals are likely necessary for difficult-to-control weeds. Going cheap can be good if the cautions mentioned previously are observed, but may not work if conditions are less than ideal.
Not calibrating the sprayer. Sprayer calibration should be performed every season, Funderburg says, because calculating the volume you spray is critical to knowing how much product to put into the tank. When you calibrate, also inspect nozzles, screens, lines, pump, etc., to make sure everything is okay.
Not reading the label. Failure to follow label directions not only leads to poor weed control, it violates federal law. Funderburg says that "following the directions on the herbicide label is about the closest thing to getting a guarantee on weed control I can come up with." For more on weed control, contact Noble Foundation's Ag Helpline at 580-224-6500, or visit www.noble.org/Ag/Research/Forages.htm. -- Joe Roybal