By Eric Hoff and Haley Bloomquist, The Nature Conservancy, Brown Ranch, North Dakota.
Leafy spurge is native to Eurasia and thought to have been brought to the upper Midwest in the late 1800’s. A very aggressive plant, Leafy Spurge spreads through rhizomes as well as seeds. Exploding seed pods have been shown to spread seed up to 20 feet from the parent plant! Seeds are also viable in the soil for as long as 10 years.
Here at Brown Ranch in North Dakota, Leafy Spurge is found from the top of our sandhills right down to the very edge of the wetlands/ sedge meadow. It does not like to be submerged in water or heavily saturated soils but can withstand a short duration of inundation.
Leafy spurge can flower in the spring and fall. The control of Leafy Spurge is very difficult because of its extensive root system, which can be up to 26ft in depth, as well as the longevity of the seeds. There are many integrated pest management tools to control Leafy Spurge which include chemical, mechanical, and biological methods. The most common and effective herbicides to combat Leafy Spurge include Tordon, Plateau, 2,4-D, and Facet. At Brown Ranch we have found Plateau and Facet are the most effective at controlling Leafy Spurge. Plateau is hard on forbs and caution must be used in areas where the water table is or can be at or near the soil surface. Facet is not as hard on forbs, is equally or more effective, but costs almost twice as much as Plateau. As with many herbicides, care should also be taken when applying Facet to areas where the water table is at or near the surface.
Another option for control is mechanical treatment. Land managers have successfully used weed whips for smaller areas and large tractor mounted mowers to control the plant by keeping it from setting seed. Mechanical treatment is often followed by an herbicide treatment later in the summer or fall.
A third option for control is utilizing biocontrol agents such as the flea beetle. Flea Beetles have been found to be very cost effective in places where the beetles can over winter. Here in the Sheyenne Delta, the soils are often too sandy for the beetles to establish their larvae in the root system to survive during the winter months. Other biocontrol agents include livestock. While Leafy Spurge can be toxic to cattle and horses, these species are best used to remove desirable vegetation prior to chemical application. This helps increase chemical reception of the intended target. Unlike cattle, goats and sheep can graze Leafy Spurge without worry of toxicity and provide effective control by reducing the vigor of the plant and preventing it from setting seed early in the season.
One last tool that may be utilized is prescribed fire. Leafy Spurge responds well to fire, so why would it be a useful tool? At Brown Ranch we use fire to delay the onset of seed, thus extending our pre-seed spraying season. Because leafy spurge responds well to fire, it grows with vigor, which often means it is one of the first plants to emerge and one of the tallest, making it an easy target for chemical application. Because it is actively growing, that chemical is readily adsorbed and translocated to meristematic tissues.
If unmanaged, Leafy Spurge can out compete native vegetation and can become a monoculture (see photos below of managed vs. unmanaged). The good news is, with dedication, good timing and integrated pest management practices you can control Leafy Spurge and have healthy diverse prairies!
Above is prairie managed for Leafy Spurge
Above is unmanaged for leafy spurge
NEWS: Due to Covid 19 crisis we are postponing the GRN workshop of this August to next August, 2021 in Barrington, Illinois.