Managing Weeds in Wheat (A. Stanley Culpepper)

With a warm December, numerous winter weeds are up and growing aggressively.  For wheat that was planted timely, herbicide applications are usually needed around Christmas.

Broadleaf weeds are common in wheat but can be managed effectively if herbicide applications are timely. Numerous herbicide options exist and six of these options are shown below.

Herbicide Option	Wheat Stage of Growth	Weeds
Harmony Extra1 + MCPA2 or Harmony Extra1 + 2,4-D2	Fully tillered	Wild radish, henbit, chickweed, primrose, and most other broadleaf weeds.
Harmony Extra1 followed by MCPA or 2,4-D	After 2 leaf & before flag leaf followed by fully tillered
Harmony Extra1	After 2 leaf & before flag leaf	Henbit, chickweed, most other broadleaf weeds EXCEPT primrose and radish larger than 1”.
2,4-D or MCPA	Fully tillered	Wild radish and primrose.
PowerFlex	Three leaf but before jointing	Wild radish, ryegrass and less than 1.5” henbit or chickweed
Osprey	Emerged but before jointing	Ryegrass, annual bluegrass, and less than 2” henbit or chickweed

¹Harmony Extra, Harmony Extra Total (Sol) and generic products are available, use correct rate.

²MCPA or 2,4-D can be applied at 12-16 oz/A; MCPA is “softer” on wheat.

Annual ryegrass is a serious pest of wheat, especially in middle and North Georgia, primarily due to herbicide resistance.  Growers must rotate herbicide chemistry. Osprey and PowerFlex have the same mode of action thus rotating these herbicides is not an effective approach in rotating herbicide chemistry.  Osprey/PowerFlex should be rotated with Axial; a piece of land should never be treated two years in a row with PowerFlex/Osprey OR Axial.  In addition to rotating herbicides, one must implement cultural practices such as tillage (deep tillage helps considerably) and crop rotation (allowing use of other herbicides such as Roundup) in a ryegrass management program.  There are Georgia growers with ryegrass resistant to Axial, PowerFlex, Osprey, and Hoelon and the production of small grains is no longer economically feasible.  Ryegrass will develop resistance to herbicides more quickly than any other known plant.

All “ryegrass” herbicides should be applied prior to 2 tiller ryegrass!  Mixtures with Harmony will improve broadleaf weed control; however, do not mix these products with 2,4-D or MCPA.

Herbicide Option	Wheat Stage of Growth	Weeds in Addition to Ryegrass
Axial XL	Two leaf up to pre-boot.	None
PowerFlex	Three leaf up to before jointing.	Wild radish < 6”, henbit and chickweed < 1.5”
Osprey	Before jointing.	Annual bluegrass; wild radish < 4”, henbit or chickweed < 2”