As temperatures begin to rise, pasture forages start to experience significant growth . . . but inevitably, so do weeds.

Bill Curran, professor of weed science at Penn State University, notes that weed control is essential during the grass establishment to avoid competition with desired species – but don’t be too quick to fill the sprayer. Curran recommends seedling forage grasses be allowed to get established, reaching 4 to 5 inches tall with a good vigor and a strong secondary root system.

Once well established, plant growth regulator type herbicides such as 2, 4-D, Clarity, Crossbow, and ForeFront can be applied. Cimarron Plus also has establishment periods that are important to observe before herbicide application.

Most herbicides used in grass forage crops will seriously injure or kill legumes, so it is important to weigh costs. “Don’t use these products if loss of legume species cannot be tolerated,” says Curran in a recent edition of Penn State’s Field Crop News.

For managing thistles, an effective spraying time is during the bud to bloom stage. Biennial thistles, such as musk, bull, and plumeless are typically more susceptible to plant growth regulator herbicides than Canada thistle, which has a perennial life cycle and spreads from underground rhizomes.

Excellent results for controlling Canada thistle can be achieved with herbicides such as Forefront, Milestone, and Stinger, but be sure to read all label precautions before applications are made.

Woody species, including honeysuckles, brambles, black locust, multiflora rose, and autumn olive can be aggressive in the warming weather. “Crossbow or generic versions such as Crossroad or Candor can be used for most woody perennials since the active ingredient, triclopyr, is pretty effective on these species,” states Curran.

Metsulfuron or Cimarron products can help control multiflora rose, honeysuckle, and dewberry. Usually, 2, 4-D, and dicamba aren’t as effective on woody species, but weed suppression can occur if they are tank-mixed and used at higher rates.

A good time to apply herbicides to woody weeds is when they begin to bloom. Curran says that other tactics can be used to control these weeds, but usually a combination of methods is needed to harness control.

Mechanical control methods, including mowing and excavating, can be effective but are more time-consuming and laborious.

Curran notes that for multiflora rose, specific techniques with biological controls have been used. One prominent biocontrol agent is rose rosette disease (RRD), a virus that is slowly spreading in Curran’s region of the country. It usually causes infected multiflora rose plants to die within two years. If feasible, goats and sheep can be helpful in managing multiflora rose plants as well.

“No matter which control tactic is used, follow-up maintenance practices are a must for long-term control,” states Curran. “Removing dead brush, annual mowing, and adequate soil fertility are examples of practices to maintain control of woody weed species.”

Contact your local or state extension office for specific information about controlling the troublesome weeds in your pastures. Always read and follow label directions when applying herbicides.

Sydney Sleep

Sydney Sleep grew up on her family’s Angus operation outside of Spearfish, S.D. She is currently attending South Dakota State University where she is pursuing a degree in agriculture communications. At college, Sleep is an ambassador for the SDSU College of Agriculture and Biological Sciences, is a member of Sigma Alpha professional agricultural sorority, and works as the communications assistant for the College of Agriculture and Biological Sciences. She is serving as the 2016 Hay & Forage Grower summer editorial intern.