Many options to control brush, woody plants in pastures

DUBUQUE, Iowa — Cattlemen have several options to control brush or woody plants in pastures.

“When we have infested pastures, we get large reductions in forage biomass,” said Mark Renz, professor and Extension specialist at the University of Wisconsin-Madison. “We can easily get 50% less forage in an invaded pasture versus a non-invaded pasture.”

“Data from a moderately invaded pasture with 10% to 20% brush cover shows if we mowed or sprayed we would double the forage that is available,” said Renz during a presentation at the Driftless Region Beef Conference, hosted by the University of Illinois Extension, Iowa State University Extension and Outreach and University of Wisconsin-Madison Extension.

“As a rule of thumb, your pasture should have less than 5% woody plants,” he said. “If you take 100 steps in your pasture, five of the steps or less should be near a shrub and ideally it’s best to have no shrubs at all.”

Cattlemen have several options for managing shrubs in pastures, including removing the entire plant, removing some or all of the above-ground tissue or using herbicides.

“All of these can work if utilized correctly,” Renz said.

“Removing the entire plant can be very effective with weed wrenches that attach to the bottom of the shrub and pull it out of the ground,” he said. “It works on buckthorn or honeysuckle when they are small.”

Removing the entire plant is effective on species with simple root crowns.

“But if you have a creeping perennial root system like black locust, it is not going to work because you can’t remove all the below-ground tissue,” Renz said.

Mowing can control shrubs in pasture and if there is a large infestation, cattlemen can rent a forestry mower.

“They’re great, but rental rates can be from $100 to $150 per hour,” Renz said. “The biggest negative is the shrubs will regrow, so you’re going to need to do additional management like using herbicides.”

Goats will feed on the leaves and strip the bark off of shrubs.

“We’ve been doing work where we’re trying to introduce silvopasture into a forest, so we’ve been renting goats and grazing 35 to 40 goats per acre,” the university professor said. “That costs from $900 to $1,500 per acre, but if you own your own goats, that cost would be much less.”

Goats remove vegetation, but they don’t kill the shrubs, Renz said, unless the goats graze the pasture for several years.

“We think it’s somewhere between three to six years depending on the shrubs,” he said.

Prescribed burning is a technique that will suppress shrubs.

“The big negative is you have the hazard of containing the fire to make sure it doesn’t move offsite,” Renz said.

“The shrubs will resprout, so you have to get the fire hot enough to burn the shrub, and depending on when you burn, you might lose some early season biomass.”

Herbicides are often the first tool cattlemen use for controlling shrubs because they can provide really good control with one application.

“But we need to get training on how to use herbicides correctly because a lot of bad things can happen if we miss apply them,” Renz said.

Foliar applications of herbicides are the most common.

“Spread the herbicide on the leaves to the point of runoff,” Renz said. “The biggest mistake is people apply too much, because if it’s dripping off the leaves, you’re wasting herbicide and money.”

It is important to apply the herbicide around the entire shrub.

“If you don’t, the herbicide won’t be shared across the whole plant and it might just kill half the shrub,” Renz said. “Make the application when the plant is actively growing in the spring to fall and when it is fully leafed out.”

A cut surface application can be done anytime of the year.

“Cut the stem and then apply the herbicide to the cut surface,” Renz said. “If it’s a small stem, treat the whole cut surface, and if it’s a large stem, only treat the outside edge.”

Depending on the herbicide, it can be mixed in water or basal bark oil.

“If you’re using glyphosate, you have to mix it with water because it does not mix in oil,” Renz said. “Do not do this on woody plants that have a creeping root system because the cutting promotes resprouting.”

Basal bark application can also be applied anytime of the year.

“The only real difference is we’re not cutting down the plant,” Renz said. “We’re applying a concentrated solution in a band 12 to 18 inches around the entire circumference of the stem.”

This technique works best on smaller diameter shrubs.

“Read the label for rates and restrictions,” Renz said. “Don’t apply when you have excessive snow because you’ll get some herbicide on the snow, and when the snow melts, the herbicide will move off site.”

For larger trees, the hack-and-squirt method works really well.

“You use a hatchet to put a cut in the tree at a 45-degree angle and then spray a concentrated solution into the cut,” Renz said.

“The key is the number of hacks you do is dependent on the diameter of the woody plant and this is probably not a good option for multiflora rose.”

All these approaches work, the Extension specialist said.

“It’s about figuring out which ones fit best in your system and your pasture management,” Renz said.

“We recommend getting some help from an expert on picking herbicides and make sure you are selecting a herbicide registered for use in pastures,” he said.

“They will have specific restrictions for grazing that can vary dramatically and many of these products have manure restrictions.”

Renz advises cattlemen to read the fine details to understand the restrictions.

“It can get confusing really quick, so if you have questions, ask for help,” he said.