via DTN/The Progressive Farmer

by Becky Mills, Progressive Farmer Contributing Editor

Remove a pound of weeds from your pasture and in most cases you’ve just added a pound of forage. That’s the best argument for doing away with pasture weeds you’ll ever hear.

It’s simple, says Eddie Funderburg. “The No. 1 reason to control [weeds] is loss of grazing.”

Funderburg, an agronomist with the Ardmore, Okla.-based Noble Foundation, says, “Here in our area, in unfertilized pastures, we usually produce about 2,000 pounds of dry matter per acre per year. If half of that is weeds, that’s a thousand pounds.”

He admits, “Cattle will eat most weeds when they are young and tender. But when they get larger they lose their palatability. If cattle would eat them, we wouldn’t call them weeds.”

There’s also the issue of quality over quantity. North Dakota State University agronomist Rodney Lym says, “Most weeds are not high in protein and other nutrients livestock need, so you’re losing quality as well as quantity of grazing.”

Saluda, S.C., producer Brad Forrest adds, “Cattle can’t graze under weeds like horsenettle because it sticks them. That makes the grass under the weeds useless.”

Convinced? Here is a list of tips for controlling those less-than-desirable plants.

1. Don’t overgraze. Rotate your pastures. Overgrazing is the biggest cause of weed problems. The desirable forages weaken and the weeds move in. Pastures need rest. Shawnee, Okla., cattleman Don Johnson agrees. “Rotation very much helps keep weeds down,” he says. “I have 2-acre grazing cells of bermudagrass that look like a yard.”

Since he rotates cattle frequently, Johnson is on constant patrol for the occasional weeds that do pop up. When he spots them, he zaps them immediately with a hand sprayer he keeps on his four-wheeler.

2. Identify weeds. The Noble Foundation has an online guide for forage and weed identification. Go to the plant image gallery at http://www.noble.org/WebApps/PlantImageGallery/Index.aspx. Knowing which weed you’re trying to control can help you make the best management decision.

3. Use the right herbicide. Based on the weed, evaluate your options, taking price and efficacy into account.

4. Calibrate your sprayer. If you don’t know how much herbicide you’re applying per acre, it is hard to mix the herbicide accurately. Put out too much and it can hurt your grasses. Put out too little and you’re wasting your time and money.

To make sure he has his sprayer calibrated properly, cattleman Johnson says he puts in 15 to 20 gallons of water and sprays it on his pasture. “When you run out you can measure how much ground you’ve covered,” he explains. “It is simple to do.”

In addition, don’t forget to read the herbicide label and follow the directions for use and mixing.

5. Spray at the right time. Timing depends on the weed. As a general rule, spray weeds when they are young and actively growing. There are a few exceptions. With blackberries and nightshades, or nettles, for example, you need to wait until they are mature and in full bloom.

6. Watch the weather. There has to be enough moisture in the soil for the weeds to be actively growing so they’ll take up the chemical.

7. Don’t forget your mower and biologicals. “We try to mow every pasture at least once a year unless we graze it down close or hay it. That helps control some of the weed species,” says Forrest.

That is particularly true with greenbrier, says agronomist Funderburg. “If it is in a place where you can mow, you can get pretty good control. We’ve had fair luck with herbicides, but mowing works better than chemicals and is cheaper.”

In North Dakota, the green approach is really working. Lym says, “Biological control of leafy spurge with flea beetles has been very successful.”

For more information on the use of flea beetles to control leafy spurge, see http://www.ag.ndsu.edu/pubs/plantsci/weeds/w1183w.htm.

Legumes and weed control

If you are trying to keep legumes in your pastures but get rid of the weeds, be forewarned: It isn’t easy.

Noble Foundation agronomist Eddie Funderburg says, “Be really careful with herbicides containing picloram. It is found in Tordon and Grazon P+D. Also avoid the aminopyralids. They are found in Milestone and GrazonNext. These chemicals have quite a bit of residual activity and are harsh on legumes.”

He suggests, “Use a product that has little soil activity like 2,4-D. And wait until the legumes have set hard seed. In clovers that flower, that is when at least half the flower has turned brown. Then spray.”

Unfortunately, there always seems to be a drawback. “By waiting, the weeds get large and you won’t get as good control.”

“It is a fight,” says Saluda, S.C., producer Brad Forrest. “We’ve had so many dry years that we’ve had to put clover on the back burner and concentrate on the weeds. We might have to bite the bullet and destroy the clover to kill the weeds. But some of the herbicides have a long carryover—up to a year.”

Funderburg says there are times when starting over is the best option. “Try to get your field cleaned up before you plant legumes, but don’t use the products I cautioned against because of their residual activity.”