Weed control in winter wheat: Timing is everything

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Late-fall planting in certain areas of the state and unpredictable weather conditions have been
troublesome for some of the 2017 winter wheat crop. These challenges have left Michigan winter
wheat fields at various stages. In fields where herbicide applications have not been made, it is
important to understand what the cutoff application stages are for the different herbicides.
Herbicide applications after these stages can lead to excessive crop injury and reduce yield. Below
is a review of the maximum application timings and weed control strengths for commonly used
winter wheat herbicides.

Feekes growth stage 6: Feekes stage 6, also referred to as jointing, is the first application cutoff
for several winter wheat herbicides. Among these are several of the plant growth regulator
herbicides including: 2,4-D (amine and ester formulations), dicamba (Banvel or Clarity), MCPA,
and Curtail (2,4-D amine + Stinger). These herbicides are typically good on summer annual weeds
like common lambsquarters, pigweed, and common ragweed, but vary in their control of some of
the more common winter annual weeds like common chickweed. 2,4-D, MCPA, and Curtail will
not control chickweed. Osprey, PowerFlex HL, and Puma are other herbicides that need to be
applied prior to Feekes stage 6. These herbicides are our best options to control several grass
weeds, like windgrass, in winter wheat. PowerFlex also has good activity on some broadleaf
weeds, including common chickweed. If winter wheat is at jointing these herbicides should no
longer be used.

Feekes growth stage 7.9: Feekes stage 7.9, just prior to flag leaf emergence, is the next application
cutoff for certain herbicides. Affinity BroadSpec, Harmony Extra, Harmony, Express, Huskie,
Axial XL, and the new herbicide Quelex can be applied to wheat until just before the flag-leaf is
visible. Affinity BroadSpec, Harmony Xtra Harmony, Express, Huskie, and Quelex all provide
good to excellent control of common chickweed and several other winter and summer annual weed
species. Axial XL can be used to control grasses, including annual ryegrass and windgrass, in
winter wheat.

Feekes growth stage 9: The last application cutoff window for herbicide applications in winter
wheat is Feekes stage 9, just prior to the boot stage. Herbicides that can be applied up to this point
include: Buctril, Stinger, Starane Ultra, and Widematch (Stinger + Starane). These herbicides will
control broadleaf weeds, however many have a fairly narrow weed control spectrum. For example,
Buctril provides better control of summer annual weeds, but is not very effective against winter
annual weeds. Starane Ultra has a very narrow weed control spectrum, but is excellent in
controlling hemp dogbane. Stinger, on the other hand, provides excellent Canada thistle control.

For more information for control of winter and summer annual weeds including windgrass
control can be found in Chapter 3 of the MSU 2017 Weed Control Guide for Field Crops
(E0434) 2017 Small Grains Weed Control Guide Pages

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