Herbicide Recommendations for Winter Small Grains

Dense populations of winter annual weeds (e.g., common chickweed, henbit, marestail, winter annual grasses, and others) can compete with fall-seeded small grains in late fall and early spring and slow the rate of crop development, potentially reducing yield. Harmony Extra (or generic equivalent) is still one of the most widely used broad-spectrum herbicides for broadleaf weed control. Fall applications have been more consistent than spring applications for weed control in regional trials. However, it has its weaknesses, and other options or tank-mixes should be considered. The table below summarizes common fall herbicide options for small grains. Here are some "best bets" for common problem weeds:

• Common chickweed: Harmony Extra and Quelex are still effective on it in many parts of the region; however, there are pockets of resistant populations starting to thrive. Tank-mix with Starane Ultra/Pixxaro or include Metricor (metribuzin) in your spray program if ALS-resistant (Group 2) chickweed is prevalent. It might be best to make fall applications to control chickweed since it tends to get unruly by spring.
• Marestail: products such as 2,4-D, dicamba, Huskie, Quelex, and Stinger applied POST have activity on this weed, especially when applied to smaller (<4" tall) marestail.
• Speedwell species: there are several speedwell (Veronica) species, including corn, common, ivyleaf, and others in our area. Depending on the species, their life cycle is either annual or perennial. Many of the commonly used small grain herbicides provide little or no control of speedwell. Harmony Extra + Quelex or Starane Ultra has provided control of ivyleaf speedwell (better than the herbicides applied alone). Finesse has a few annual and perennial speedwells listed on its label and usually provides about 80% control of them. If the speedwell is small, PowerFlex HL, Aim, or Metricor provides suppression.
• Brome species (downy brome, chess, cheat): the most consistent herbicide options include Anthem Flex/Zidua, Osprey (Xtra), and PowerFlex. Finesse and Metricor can provide suppression of it. Outrider in wheat is effective on brome weeds, but its strict rotational crop options limit its utility in our region.
• Annual ryegrass: Anthem Flex/Zidua, Axiom, Osprey (Xtra), and PowerFlex HL tend to be the most effective on this weed, while Prowl, Finesse, and Axial have activity but are less consistent.
• Annual bluegrass: active herbicides include Axiom, Anthem Flex/Zidua, Metricor, Finesse, Osprey (Xtra), and PowerFlex HL.
• Roughstalk bluegrass (RSBG): Since it primarily emerges in the fall, that is a good time to apply an effective herbicide before it grows more than 2 tillers. In some cases, early spring applications can provide better control if RSBG is still emerging during that time of year and is less than 4 inches tall or if it was missed by a fall herbicide treatment. Either way, fall and/or early spring applications provide better control than late spring treatments. Studies at Michigan State University indicate that Osprey, Axial XL/Bold, and PowerFlex HL provide control of this weed. However, Osprey applied to RSBG (1-2 inches tall) in the fall or early spring provided the most consistent control. Fall treatments provide effective initial control (>90%) from these products, but spring emergence of RSBG can lead to escapes by harvest. A study in Ontario, Canada comparing similar treatments showed that early spring treatments tended to be better than fall treatments. Late spring applications are usually not as effective since RSBG is too large (>4 inches tall). One suggestion would be to apply an Osprey product in the fall and then PowerFlex HL, metribuzin, or Axial XL/Bold in the spring to get adequate control of this species. Since, according to the Osprey and PowerFlex HL labels, no more than one application can be made during the growing season to a fall-sown wheat field. The spring application must be sprayed early when the RSBG is still small (i.e., 3 inches tall). If Osprey (Xtra) was not applied in the fall, then an early spring application should provide good control of RSBG. If you intend to double-crop soybeans after wheat, be aware of herbicide rotational restrictions.

Grassy weed control considerations. When controlling weedy grasses in wheat, it may be necessary to tank-mix residual products like Anthem Flex/Zidua with those that have foliar activity, such as Osprey (Xtra), PowerFlex HL, Finesse, or Axial products, to obtain control of existing grassy weeds that have already germinated. These tankmixes are typically applied as a delayed PRE (i.e., a few days after planting) or as an early POST (spike to early tillering stages) treatment in the fall.

BMPs for effective herbicide applications. Consider these factors, which are specified on the product label, to optimize the spray application – correct adjuvants, spray coverage, and environmental conditions. Simply put, make sure to include the necessary spray adjuvants, otherwise reduced control will result. Most of these products require the inclusion of a nonionic surfactant (NIS), methylated seed oil (MSO), crop oil concentrate (COC), and/or ammonium sulfate (AMS) or other nitrogen fertilizer to improve efficacy. It is best to apply them in a spray volume of 15 to 20 gallons per acre to provide thorough and uniform spray coverage on the weeds. If weeds are not actively growing due to poor growing conditions or the foliage is excessively wet, decreased herbicide effectiveness may result. Remember that cool (less than 50°F) cloudy days can reduce herbicide activity. Also, if you plan to frost-seed or drill a companion crop such as red clover in early spring, make sure to follow herbicide recrop restrictions.

*Check the current herbicide label for the latest use information. Generic options are available for some of these products.