Watch winter wheat growth prior to applying herbicides

Christy Sprague

Recent rains have brought most field work to a halt. However, as most of us are waiting to get into the field winter wheat has continued to grow. Knowing what stage your wheat is at is critical when it comes to making decisions on what herbicide to use for weed control.

There are several herbicide options available that growers can use for weed control in winter wheat. However, not all of these herbicides have the same weed control spectrum or application timing. As growers look for weed control options they need to keep in mind that herbicide choices need to be based on what weeds are in the field and more importantly the stage of wheat growth. Late herbicide applications can lead to excessive herbicide injury that can cause kernel abortion and blank wheat heads, ultimately reducing yield. Plant growth regulator herbicides including 2,4-D amine and ester, dicamba (Banvel or Clarity), MCPA, and Curtail (2,4-D amine + Stinger) all need to be applied prior to winter wheat jointing (Feeke’s stage 6). In many areas of the state wheat is quickly approaching this stage. These plant growth regulator 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. With the warmer weather conditions it is important to scout fields and make sure that wheat has not exceeded the maximum growth stages in which these herbicides may be applied.

Herbicides including Affinity BroadSpec, Harmony Extra, Harmony, and Express do not have the same restrictions as many of the plant growth regulator herbicides. These herbicides can be applied when the wheat is at the 2-leaf stage (Feeke’s stage 1.2) to just before the flag-leaf is visible (Feeke’s stage 7.9). All of these herbicides also have better control of common chickweed than many of the growth regulator herbicides. Peak another herbicide is also an option for common chickweed control, however longer rotation restrictions (22-months) to many crops including soybean often restrict the use of this herbicide.

Another herbicide that will provide good control of common chickweed and has activity on some of our common winter annual weeds is the newly registered herbicide Huskie. Huskie also has a longer application window than the plant growth regulator herbicides (i.e., 2,4-D and dicamba). The application window for Huskie is from 1-leaf wheat up to flag leaf emergence (Feeke’s stage 1 to 7.9).

Buctril, Stinger, Starane, and Widematch (Stinger + Starane) are other herbicides that will control broadleaf weeds in winter wheat. These herbicides have the longest application window. They can all be applied to winter wheat up to the boot stage (Feeke’s stage 9). However, many of these herbicides have fairly narrow spectrums of weed control. Buctril provides better control of summer annual weeds and is not very effective against winter annuals. Starane has a very narrow weed control spectrum, but is excellent in controlling hemp dogbane. Stinger, on the other hand, provides excellent Canada thistle control. More information for control of winter and summer annual weeds including hard-to-control grasses, like annual bluegrass, cheat, and windgrass can be found in the MSU Weed Control Guide for Field Crops (E-434)

April 30, 2009