Populations of winter annual weeds spring to life in late March and early April. And Penn State Weed Specialists Bill Curran and Dwight Lingenfelter say now's the time to jump these small grain yield-sappers.
If common chickweed, henbit, purple deadnettle, horseweed and others emerge unchecked with the small grain, potential impact on yield could be great – especially with local July wheat bids now in the neighborhood of $6.40 a bushel.
Here are Curran's and Lingenfelter's weed control recommendations. First though, remember that early-spring herbicide response can be slow under the typically cool conditions in March and early April. Application on cool (less than 50 degrees Fahrenheit) cloudy days aren't likely to effectively control dandelions or Canada thistle. These weeds would be more effectively controlled with a later spring application.
Harmony Extra is still probably the most broad spectrum herbicide for broadleaf control. Harmony SG doesn't have the same weed control spectrum.
Clarity, Banvel, 2,4-D, or MCPA can improve the control of some winter annuals and perennials. Stinger is the most effective small grain herbicide for thistles.
Harmony SG or Harmony Extra should be included where control of chickweed is desired. They're the only herbicides that control this weed. But if it is ALS-resistant chickweed, you'll need to include Glory or Starane. Consider using 2,4-D and Clarity if horseweed/marestail is a problem in small grains.
Grasses growing more troublesome
Weedy grasses, such as downy brome, cheat, annual bluegrass, annual ryegrass, and roughstalk bluegrass are becoming more of a problem. Wheat herbicides available for control of grasses – Axial, Finesse Grass and Broadleaf, Maverick, Osprey and PowerFlex – are most effective when fall-applied. Some of them can work during spring, but the weeds must be small.
Broadleaf herbicide choices
Once wheat has passed Feeke's Stage 6 (when the first stem node is visible), risk of herbicide injury from 2,4-D, MCPA, Banvel/Clarity, or Curtail increases. Then, these herbicides aren't recommended.