Pasture Weed Management
By: Justin Hunter | Agronomy Sales
Whether a pasture provides forage for beef cattle, dairy cattle, sheep, goats or horses, a good pasture management program will enhance the productivity and health of the animal. The negative impact of weeds in pastures is one management factor that can be difficult to quantify. Although it may be hard to measure, weeds in pastures are undesirable because of their competition with forages, often poor nutritional quality and potential for toxicity. Pasture rotation, stocking rates, seeding/planting timing, fertility, mowing practices and herbicide use all affect weed populations and species present. Herbicides are commonly used in pastures to control broadleaves (including thistles) and woody species (PennState Extension, 2001). Herbicide use often draws attention and many questions, so a deeper dive into this particular weed control strategy may provide beneficial information to help make better, more informed decisions this spring.
One of the most troublesome broadleaf weeds to control is Canada thistle. Canada thistle is a perennial weed that propagates through creeping rhizomes and wind-blown seeds. New seedling germination takes place in both the late spring and early fall — which are the most critical times for herbicide treatment (Cornell University, n.d.). GrazonNext® (Gunslinger AMP is the generic version) is a popular herbicide used in pastures to control broadleaf weeds, such as common burdock, curly dock, wild carrot and many species of thistles. It is popular because of its burndown effectiveness, residual control and animal safety. With minimal grazing restrictions, GrazonNext® provides a great opportunity to treat many tough-to-control weeds in pastures.
An example of a well-known woody weed species is multiflora rose. This prickly-stemmed shrub is spread by both seeds and root sprouting. The seeds are mostly dispersed by animals (especially birds) who eat the fruit and spread seeds through their droppings. These seeds can remain viable in the soil for up to 20 years (PennState Extension, 2020). Remedy®/Remedy® Ultra is an example of an herbicide that has good activity on woody species, such as multiflora rose, locust trees, poison ivy, poison oak and Virginia creeper. The active ingredient in Remedy®/Remedy® Ultra is triclopyr which can also be found in premix products such as Crossbow® (triclopyr + 2,4-D). The best time to treat woody species with herbicides is either through a foliar application during the mid-late flowering stages or by basal bark and cut stem treatments.
You should always read and follow the herbicide label before making treatment applications. The label will state grazing restrictions, crop rotation intervals, weed species it controls, mixing instructions, use rates and more. Also, many of these products recommend adding adjuvants, such as a non-ionic surfactant to enhance herbicide activity. One thing to note is that many herbicide products intended to control broadleaves and woody species will also take out desired clovers and other legumes so always be informed before applying.
Pasture systems are complex and often require a combination of management strategies to reach the best outcomes. Herbicide use is just one of the many weed management control strategies available; however, it is convenient, effective and will get you on the right track. As always, if you have any questions on pasture management — from fertilization and seeding to weed control — please contact your Stutsman agronomist.
Sources
Cornell University. (n.d.). Canada thistle. https://blogs.cornell.edu/weedid/canada-thistle/
PennState Extension. (2020, February 24). Multiflora rose. https://extension.psu.edu/multiflora-rose
PennState Extension. (2001, January 1). Weed management in pasture systems. https://extension.psu.edu/weed-management-in-pasture-systems#Competition