By Christy Sprague, Michigan State University Extension, Department of Plant, Soil and Microbial Sciences
Timely herbicide applications are important for weed control in winter wheat this spring.
Most of the 2015 wheat crop faired considerably well over the winter. Over the next couple of weeks, many of these acres will be treated with herbicides for weed control. While there are several herbicide options available for use in wheat, there are many factors that growers should consider prior to deciding when to spray and what products to use.
Cold temperatures
The colder than normal temperatures that we have experienced over the last couple of days should have kept most sprayers out of the field. Most herbicides labeled for weed control in winter wheat have specific instructions that applications should be made when weeds are actively growing. Herbicides should not be applied when the crop is under stress from very cold temperatures, when there are wide fluctuations in day/night temperatures, when a frost has occurred or when temperatures are below freezing prior to, at, or immediately following herbicide applications. A good rule of thumb is to only apply herbicides to winter wheat when the daily temperature is 50 degrees Fahrenheit or higher.
Winter wheat growth stage and weeds controlled
All herbicides have a maximum wheat growth stages for application listed on the label. Late herbicide applications can lead to excessive crop damage that can cause kernel abortion and blank wheat heads that can ultimately reduce yield. Some of the more restrictive herbicides that are used in winter wheat are the plant growth regulator herbicides including 2,4-D amine, 2,4-D ester, dicamba (Banvel or Clarity), MCPA, and Curtail (2,4-D amine + Stinger). The 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. All plant growth regulator herbicides need to be applied prior to winter wheat jointing (Feeke’s stage 6). Other herbicides that need to be applied prior to Feeke’s stage 6 are some of the more popular herbicides for control of grasses in wheat, like windgrass. These herbicides include: Osprey, PowerFlex HL, and Puma. PowerFlex also has good activity on many of the broadleaf weeds encountered in wheat, including common chickweed. If winter wheat is at jointing these herbicides should no longer be used.
The herbicides, Affinity BroadSpec, Harmony Extra, Harmony, Express, and Huskie, are not as restrictive as many of the plant growth regulator herbicides. These herbicides can be applied to wheat until 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.
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.