Phone calls with questions on wheat weed control have started. Some are asking how to control ALS-resistant (e.g., resistant to Harmony) chickweed. ALS-resistant chickweed is clearly becoming more of a challenge to control in wheat across the state but particularly in middle Tennessee. Other folks have asked about cleaning up just a sundry of different broadleaf weeds like henbit. Fortunately, there are two “new” herbicides that have been recently labeled in wheat that can help on these broadleaf weeds.
The first new herbicide for use in wheat is Quelex. This herbicide can be applied in the fall or spring to wheat. It would be a good option for those of you with questions on how to clean up broadleaf weeds once the soil dries. Quelex is a premix of a new active ingredient, halauxifen (Group 4 herbicide family, which also includes 2,4-D) with an ALS-inhibiting herbicide, florasulam. This herbicide has proven to be very safe to wheat in our research. The herbicide has provided very good control of ALS-resistant chickweed, horseweed, henbit and many other broadleaf winter annual weeds. Apply Quelex at 0.75 oz/A. It can be mixed with liquid nitrogen fertilizer.
The other new labeled wheat herbicide, which would be an option this fall, is Fierce. Fierce is a premix of flumioxazin (Valor) and pyroxasulfone (Zidua) and has been used for the past several years in soybean. The labeled use of Fierce in wheat is as a delayed PRE application. Specifically it can be applied to wheat at a rate up to 3.0 oz/A on wheat that is in the spike to 2 leaf stage of growth (delayed PRE). The 3 oz/A rate is not recommended in Tennessee. Research conducted in Georgia, North Carolina and Tennessee would suggest that a rate of 1.5 oz/A of Fierce has provided good weed control and greatly tamped down potential wheat injury.
A good number of folks have used Fierce this fall on their wheat, particularly in middle TN, and the weed control reports have been very good. Most notably, ryegrass and ALS-resistant chickweed are controlled with Fierce applied in the fall as a delayed PRE. Of course, the time for a Fierce application in wheat is past but it would be an option for fields infested with ryegrass or henbit this coming fall. If you intend to use Fierce this fall on your newly planted wheat make sure to plant the wheat 1 to 1.5” deep to help mitigate any potential injury.