A Weapon Against Weeds

Contact: Nevin Dawson | ndawson@umd.edu

A Weapon Against Weeds
Photo: Nevin Dawson, University of Maryland Extension

ANNAPOLIS, MD (March 2, 2011) – Invasive species got you down? Get goats! This month’s article is not about an invasive species, but a specific control measure. Goats can be a great tool in your efforts to control the invasion of many common invasive plants. Traditional control measures can be effective, but they do have drawbacks. Herbicides are generally effective in killing plants, but may inflict collateral damage on desirable species, and are viewed negatively by many landowners, managers, and citizens. This is especially true in cases where control is needed in riparian buffers or other sensitive areas. Hand-pulling is great for targeting a single species, but is very labor-intensive. Mowing is a good way to treat large areas, but only works on sites with easy access.

Goats are browsers by nature—similar to deer—and happily munch on many exotic and invasive plants without the hazard of herbicide, or the labor of hand-pulling. Some of their favorite foods include multiflora rose, kudzu, Phragmites, and Johnsongrass. Goats are a great option on sites that would be difficult to access with traditional control measures, like steep slopes and thick jungles of thorny vines.

There are some sites where goats are not a good choice. Avoid forcing goats into wet or boggy areas where hoof rot could become a problem. They can spend some time in wet areas grazing species like Phragmites (common reed), but make sure that they’re able to retreat to dry ground. Areas with lots of beneficial species dispersed among the invasives may not be suitable, unless the plants you want to keep are protected with tree tubes or exclosure fencing.

Invasive species control by goats can be an effective public relations tool and a method of raising awareness about invasive species issues at agritourism and other operations. Although some time and money is required for a successful operation, remember that the goats are still meeting the owner’s primary objectives—meat, dairy, etc.—while simultaneously providing the grazing service.

mfr pre goat
Multiflora rose before goats.
mfr after goat
Multiflora rose after goats.

Photos: Linh D. Phu, Maryland Department of Natural Resources

The type of fence you choose to contain the goats will have a big impact on the ease with which you can set up and tear down your temporary enclosure. Electric netting with self-staking posts works well in most situations. It is lightweight, fairly easy to maneuver, and affordable. Power can be supplied by a portable battery pack or by a solar charger if no outlet is available. Because the netting extends all the way to the ground, it is effective in excluding most predators as well as keeping goats from ducking under it. This type of fence requires at least a three-foot wide clearing to keep leaves and branches from touching the fence and creating a short circuit. Hog wire panels are another option, but are heavy and do not have an electrical deterrent.

Because many goats are physically able to jump over temporary fencing, it’s important to establish the fence as a psychological barrier before relying on it in the woods. You can train goats to respect the fence by first setting it up in their normal enclosure. After curiosity gets them close enough for a few zaps, they will learn to avoid the fence, and it should be able to contain them even in a new setting where they may get spooked.

Once your browsing project is underway, make sure that the goats are actually eating your target species. Just like people, goats keep an ordered list of foods in their heads with their favorites at the top and their least favorites at the bottom. They’ll generally eat their favorite plant first until it’s gone, and then start moving down the list. Luckily, many of our least favorite species are at the top of their list.

Leaving them in a certain area once the good browse is gone may lead them to nibble on the bark of young trees, possibly inflicting serious damage. Horned goats may also damage trees by rubbing. Establish a plan for moving the fence to a new area before they run out of browse material. Also ensure that a native species is taking the place of the exotic species you are removing. It may even be necessary to plant your desired species to give it a head start over the invasive exotics. Even complete eradication may be useless if you leave the site open to a new infestation.

As with most mechanical methods of vegetation control, a single season of browsing will generally not be enough to eradicate a problem species. Most plant species require at least two or three consecutive seasons of defoliation before their energy reserves and seed banks are exhausted.

If you’re interested in using goats on your land but aren’t sure where to start, contact your county extension office to get connected with a local goat producer who may be willing to transport their animals to your property for a fee. You can also search the producer directory at http://www.sheepgoatmarketing.info. A comprehensive handbook is available at http://sheepindustrynews.org/Targeted-Grazing/target.pdf.

To see goats in action, check out the goat browsing project at Adkins Arboretum in Caroline County, starting this May. Look for more information on the Adkins website at http://www.adkinsarboretum.org later in the year.

For more information about Invasive Species of Concern in Maryland, visit www.mdinvasives.org

photos available electronically on request.