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Time to Start Thinking About Smutgrass Control
June 2009
Dr. Brent Sellers - Range Cattle Research & Education Center
It's that time of year again. The rainy season is just beginning, and most everything is turning from brown to green, including our most troublesome grass weed - smutgrass. We get many questions each year concerning different cultural practices for smutgrass control. Should we mow, or burn, or anything?
We know that we can control smutgrass with Velpar. Currently, we recommend 3 qt/acre (0.75 lb ai/acre) for small smutgrass, and 4 qt/acre (1.0 lb ai/acre) for giant smutgrass. Why start thinking about smutgrass control now? Velpar works primarily through root uptake, meaning rainfall is needed to move Velpar into the soil solution so it is available for root uptake.
What about mowing and/or burning smutgrass before Velpar application? Simply speaking, there is no advantage or disadvantage to using these cultural practices before applying Velpar. Furthermore, mowing has been suggested to increase seed spread, and burning has been said to increase smutgrass seed germination. However, these practices will make smutgrass more palatable to cattle for a 1 to 3 week period, with similar forage quality to that of bahiagrass.
When is the best time to apply Velpar? The best time appears to be any time during the rainy season from July through September. Dr. Mislevy's work with small smutgrass showed similar control when Velpar was applied in late July compared to late September. Remember that rainfall is the key to smutgrass control with Velpar.
Do I need to apply an adjuvant with Velpar? This is a good question that we continue to evaluate. Most of the activity from Velpar comes from root uptake, however, there is some foliar activity. The addition of an adjuvant may aid in control if rain does not occur within a week after Velpar application. However, our data indicates that the addition of an adjuvant did not increase smutgrass control compared to Velpar alone.
Smutgrass continues to be our most problematic grass weed species in pastures. Applying Velpar will control existing smutgrass plants for at least a year. Management of the pasture after Velpar application may be the key to long-term management of smutgrass. We are currently investigating best management practices for smutgrass control.