Herbicide Options For Weed Control In Winter Wheat: Things To Consider

 

 

Over the next month, many of Michigan’s winter wheat acres will be treated with herbicides for weed control. While there are several herbicide options available for use in wheat, there are many factors growers should consider prior to deciding when to spray and what products to use.

 

 

While it looks like we are finally moving past the cold temperatures of the 2016 spring, it is important to remember that most herbicides labeled for weed control in winter wheat have specific instructions that state herbicide 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. Following this rule of thumb helps avoid possible wheat injury from herbicide applications and improves weed control.

 

 

The time-honored tradition of frost-seeding red clover in winter wheat has regained prominence for many Michigan growers. However, one of the greatest challenges for growers who are frost-seeding clover in winter wheat is in finding a herbicide that can be applied for weed control without damaging the clover. Over the past several years, with funding provided by the Michigan Wheat Program, Michigan State University has been conducting research to determine what herbicide options are available for winter wheat frost-seeded with red clover. While there are several herbicides that can be applied in the fall that have little impact on frost-seeded clover, the only herbicide that can be applied in the spring without negatively impacting clover is MCPA.

 

 

Spring conditions have generally been unfavorable for nitrogen applications to winter wheat this year. While in the next few weeks many growers will be applying nitrogen to wheat, some growers choose to split their nitrogen applications and apply a portion of their nitrogen with their herbicides. A few years ago we conducted research to determine the effect of applying the herbicides Affinity BroadSpec, Huskie and 2,4-D with 28% UAN (nitrogen) as a spray carrier on weed control and wheat tolerance. From this research we were able to formulate the following recommendations:

 

 

 

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.