Spray or Delay?
Spring arrived ahead of schedule this year, catching many producers off guard with the advanced maturity of our common winter weeds. While most of these species are typically easy to control when targeted at the correct growth stage, the recent unseasonal warmth has given them a significant jump start. Now, many of us are looking at advanced weeds and wondering: should we spray now or delay?
The Current Challenge
Take, for example, these healthy specimens of henbit and mustard recently found in a newly established fescue hayfield. In this case, the producer did his due diligence in preparing the field, sowing, and fertilizing within the appropriate time window this fall.
However, even the best-laid plans are subject to the weather. The lack of rainfall of this past fall persisted through the winter and into the spring, complicating management decisions.
The Trade-Off: Chemical Power vs. Plant Maturity
It’s tempting to look at a field of mature henbit and mustard and want to reach for a heavy hitter. Many would agree that a strong residual herbicide—such as those containing aminopyralid (like GrazonNext® HL)—would work even on these mature plants.
While you are likely right about the efficacy, we must factor in the maturity of the forage stand. Most high-powered herbicides require the grass to have at least three leaves and a healthy root system before application. This particular stand was just barely above that maturity threshold, and it seemed risky given the current drought conditions and warmer temperatures.
The “Mow vs. Spray” Decision
Beyond plant maturity, there is the critical factor of residual restrictions. Herbicides containing aminopyralid carry a significant restriction: the hay cannot be sold off the farm for 18 months. For many hay growers, this necessitates a non-residual herbicide approach.
However, at this stage of maturity, a non-residual option like 2,4-D would not provide adequate control. By this point, much of the damage—the robbing of water, sunlight, and fertilizer—has already been done by these mature weeds. While it is always satisfying to spray and watch the weeds curl and die, the current drought makes it a real challenge; we need actively growing weeds for maximum herbicide uptake.
In this case, the decision was made to wait and mow the field at a high height. This strategy offers several benefits:
- Stimulating Growth: Set the mower high to encourage some regrowth and tillering while also avoiding the energy reserves and some canopy.
- Nutrient Cycling: It leaves the nutrients in the field to break down rather than removing them in a hay crop.
- Recovery Time: A traditional hay crop is often cut shorter and later in the season, which wouldn’t allow the plant to rebound as quickly before the summer months.
Looking Ahead: Planning for Next Season
The main goal of this situation was to prepare and protect the plant for its biggest hurdle yet: summer. The fescue needs maximum root development to survive the heat and lack of rain.
As we plan ahead for next season, it’s important to remember that many of these winter weeds can be successfully controlled much earlier. Targeting them in the fall, or even during late February and early March, allows for better control while the weeds are small and before they’ve had a chance to rob your forage of vital resources.
Moving forward, they are shifting to a more rigorous weed scouting program. By catching the summer weeds as they emerge, we can ensure they are controlled efficiently and cost-effectively.
As with anything, there is no one answer that fits for everybody. Spraying may still be the best option for your situation. Feel free to reach out, and let’s discuss a plan.
Christopher LeMaster
Area Livestock & Forages Agent
CLEMAST@CLEMSON.EDU
