![]() ![]() In addition, the use of surfactant (required with herbicides such as Harmony Extra) greatly increases leaf burn potential. This risk increases with later wheat growth stages because more leaf area is exposed to the treatment and recovery time is shorter. Application of herbicide in liquid nitrogen can cause leaf burn from the nitrogen, especially under hot, humid conditions. The most common herbicide to be used in this manner is 2,4- D ester (2,4-D amine is difficult to mix in UAN). Liquid urea-ammonium nitrate fertilizer (UAN) is a common carrier for herbicides in wheat. A much better alternative on wheat past Feeke’s stage 6 is to use another broadleaf herbicide with a wider application window that is effective on the weeds present in the field. This risk can be minimized by applying the amine form of 2,4-D or reducing the rate of a 2,4-D ester. If growers choose to apply 2,4-D at later stages, they need to understand the associated risk. It is recommended that application of 2,4-D to wheat be made after wheat has reached Feeke’s stage 3 but prior to Feeke’s stage 6. Severe injury is highly probable when 2,4-D is applied at Feeke’s stages 9 and 10. Thus, the risk of injury increases as wheat growth stage advances between stages 6 and 9. Between stages 6 and 9, sensitivity to 2,4-D gradually increases as wheat growth stage advances. Wheat tolerance of 2,4-D is highest between Feeke’s stages 3 and 6 and is lowest in Feeke’s Stages 9 and 10. Below is a wheat growth stage graphic from the Agronomy Guide (page 346).Įach spring there are questions about the risks associated with 2,4-D or MCPA application to wheat past Feeke’s Stage 6. Buctril, Huskie, Stinger and Starane can be applied to wheat up to boot stage (before Feeke’s Stage 9). Harmony Extra and Harmony SG (and the similar products listed above) can be applied to wheat until the flag leaf is visible (before Feeke’s Stage 8). ![]() In this situation, the remaining herbicide options for broadleaf weed control are Harmony Extra (similar products: Edition, Treaty Extra, Nimble, others), Harmony SG (similar products: Treaty, Harass, Volta), Buctril, Stinger and Starane. ![]() Once wheat has passed Feeke’s Stage 6 (i.e., when the first node of stem is visible), the risk of herbicide injury from 2,4-D, MCPA, Banvel/Clarity, or Curtail increases and application of these herbicides is not recommended. Herbicide selection for broadleaf weeds in winter wheat past Feeke’s Stage 6 Some of these products can work in the spring, but to be effective, the weeds must be small. The wheat herbicides available for control of grasses, Axial, Finesse Grass and Broadleaf, Maverick, Osprey, and PowerFlex are most effective when applied in the fall. Weedy grasses, such as downy brome, cheat, annual bluegrass, annual ryegrass, and roughstalk bluegrass are also becoming more of a problem in Pennsylvania. These weeds would be more effectively controlled with a later spring application. Applications this early are not likely to effectively control dandelions or Canada thistle. Remember that cool (less than 50 F) cloudy days can reduce herbicide activity. Herbicides applied in early spring can be slow under the typically cool conditions in March and early April. Refer to the Agronomy Guide table for additional details. Consider using 2,4-D and Clarity if horseweed/marestail is a problem in small grains. Harmony SG or Harmony Extra should be included where control of chickweed is desired, since these are the only herbicides that control this weed, but if it is ALS-resistant then you will need to include Glory or Starane. ![]() Clarity, Banvel, 2,4-D, or MCPA can improve the control of some winter annuals and perennials and Stinger is the most effective small grain herbicide for thistles. Harmony SG contains only one of the active ingredients (thifensulfuron) in Harmony Extra and thus does not have the same weed control spectrum. Harmony Extra is still probably the most broad spectrum herbicide for broadleaf control. ![]()
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