Late Winter Weed Control In Wheat
DR. LARRY STECKEL
JACKSON, TENN.
There have been quite a few phone calls recently with questions on wheat weed control. A big difference from previous years’ late winter calls on wheat is that no crop inputs have been able to be applied due to all the wet weather. As such many wheat fields have well established weeds.
Most questions have concerned trying to do something with poa and ryegrass. There are not any great options to manage these two weeds in late February. At this point the best option to use on ryegrass is Axial. Control will depend upon how well established the ryegrass has become. If it is well into tiller control would be no more than 70 percent. If it is less well established 90 percent or better control can be achieved. The other wild card here is that we seem to be in the beginning stages of ryegrass developing resistance to Axial. This is not widespread across Tenn. but there are fields out there with this problem.
Poa control comes down to two herbicide options. The first is Osprey which would be the best option on poa that is well established. The other option is metribuzin. The cost for this option is less than Osprey but experience has shown that the probability of metribuzin providing much control of poa that is well established is not good.
The best time to apply herbicide to manage ryegrass and poa was either with Fierce or Zidua applied delayed post emergence last fall. Another good option for poa would have been metribuzin in the fall. However, the weather did not cooperate with us to get these applications out. But please keep these options in mind for fall 2019 wheat.
The other question has been for control of a sundry of winter annual weeds most notably henbit and ALS-resistant chickweed. Quelex is a new herbicide for wheat and would be a great option here. 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. It 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. ∆
DR. LARRY STECKEL: Extension Weed Specialist, University of Tennessee