Spring Herbicide Applications On Winter Wheat

The warmer temperatures experienced in Indiana over the past weekend and the forecast for warmer temperatures moving forward will allow winter wheat fields in Indiana to green up and resume growth.  During winter wheat green-up, there are a few field activities that need to be considered, including winter wheat herbicide applications and winter annual weed burndown applications in no-till fields.  The following information will outline winter annual weeds to look out for, weed scouting tips, crop stage restrictions, and herbicide recommendations.

Some common broadleaf weeds to scout for in your winter wheat are dandelion, purple deadnettle, henbit, chickweed, Canada thistle, wild garlic, and annual ryegrass if you are in the far southwest part of the state.  These winter annual species emerge in the fall and can remain relatively inconspicuous through the winter; however, they become competitive and troublesome during the spring if not controlled early.  Summer annual weeds such as ragweed will be of less concern in the early spring and will be outcompeted by the wheat crop if managed properly.  Grass weeds to be aware of and scouting for are: annual bluegrass, annual ryegrass, cheat, and downy brome.

Determining the severity of weed infestations in your wheat fields is key in determining the necessity of a herbicide application.  As with all agronomic crops, you should scout your entire field to determine what weed management practices need to be implemented and determine any areas of severe weed infestations.  Wheat fields that contain uniform infestations of at least one broadleaf weed and/or three grass weeds per square foot should be taken into consideration for a herbicide application to avoid yield loss and harvest interference problems.  Some fields that have less uniform infestations, but rather pockets of severe infestation should be managed to reduce weed seed production and future infestations.

When determining your herbicide program for spring applications, the stage of the wheat crop should be considered.  The majority of wheat herbicides are labeled for application at certain wheat growth stages and some commonly used herbicides have very short windows in which they can be applied.  The popular broadleaf weed herbicides 2,4-D and MCPA are efficient and economical, but can only be applied for a short period of time between tillering and prior to jointing in the early spring.  Wheat growth stages and herbicide timing restrictions are outlined in Figure 1.

If weed infestations are severe enough to require a herbicide application, the use of liquid nitrogen fertilizer solution as a carrier is a popular option for applying herbicides and topdressing the wheat crop in a single pass over the field.  Caution should be taken when using liquid fertilizer as a herbicide carrier as moderate to severe crop injury can result, especially in saturated soil conditions.  Many POST applied wheat herbicide labels allow for liquid nitrogen carriers, but require different rates and types of surfactants than if the herbicide was applied with water as the carrier.  Table 1 includes precautions to be taken when applying wheat herbicides using liquid fertilizer as a carrier; further details and directions can be acquired from the herbicide label.

Another consideration growers should take into account when planning early spring herbicide applications is the plant back restrictions to double-crop soybeans.  A large percentage of the herbicides listed in Table 1, especially those with activity on annual ryegrass and downy brome, have soybean plant back restrictions greater than the typical three-month time period between spring applications and double-crop soybean planting.  The soybean plant back restrictions greatly reduce the number of options available to wheat producers who double-crop soybeans after wheat.  Refer to Table 1 for more specific plant back timing restrictions.

The warmer temperatures experienced in Indiana over the past weekend and the forecast for warmer temperatures moving forward will allow winter wheat fields in Indiana to green up and resume growth.  During winter wheat green-up, there are a few field activities that need to be considered, including winter wheat herbicide applications and winter annual weed burndown applications in no-till fields.  The following information will outline winter annual weeds to look out for, weed scouting tips, crop stage restrictions, and herbicide recommendations.

Some common broadleaf weeds to scout for in your winter wheat are dandelion, purple deadnettle, henbit, chickweed, Canada thistle, wild garlic, and annual ryegrass if you are in the far southwest part of the state.  These winter annual species emerge in the fall and can remain relatively inconspicuous through the winter; however, they become competitive and troublesome during the spring if not controlled early.  Summer annual weeds such as ragweed will be of less concern in the early spring and will be outcompeted by the wheat crop if managed properly.  Grass weeds to be aware of and scouting for are: annual bluegrass, annual ryegrass, cheat, and downy brome.

Determining the severity of weed infestations in your wheat fields is key in determining the necessity of a herbicide application.  As with all agronomic crops, you should scout your entire field to determine what weed management practices need to be implemented and determine any areas of severe weed infestations.  Wheat fields that contain uniform infestations of at least one broadleaf weed and/or three grass weeds per square foot should be taken into consideration for a herbicide application to avoid yield loss and harvest interference problems.  Some fields that have less uniform infestations, but rather pockets of severe infestation should be managed to reduce weed seed production and future infestations.

When determining your herbicide program for spring applications, the stage of the wheat crop should be considered.  The majority of wheat herbicides are labeled for application at certain wheat growth stages and some commonly used herbicides have very short windows in which they can be applied.  The popular broadleaf weed herbicides 2,4-D and MCPA are efficient and economical, but can only be applied for a short period of time between tillering and prior to jointing in the early spring.  Wheat growth stages and herbicide timing restrictions are outlined in Figure 1.

If weed infestations are severe enough to require a herbicide application, the use of liquid nitrogen fertilizer solution as a carrier is a popular option for applying herbicides and topdressing the wheat crop in a single pass over the field.  Caution should be taken when using liquid fertilizer as a herbicide carrier as moderate to severe crop injury can result, especially in saturated soil conditions.  Many POST applied wheat herbicide labels allow for liquid nitrogen carriers, but require different rates and types of surfactants than if the herbicide was applied with water as the carrier.  Table 1 includes precautions to be taken when applying wheat herbicides using liquid fertilizer as a carrier; further details and directions can be acquired from the herbicide label.

Another consideration growers should take into account when planning early spring herbicide applications is the plant back restrictions to double-crop soybeans.  A large percentage of the herbicides listed in Table 1, especially those with activity on annual ryegrass and downy brome, have soybean plant back restrictions greater than the typical three-month time period between spring applications and double-crop soybean planting.  The soybean plant back restrictions greatly reduce the number of options available to wheat producers who double-crop soybeans after wheat.  Refer to Table 1 for more specific plant back timing restrictions.

 

Table 1. Spring applied wheat herbicide rates, crop stage restrictions, weed control spectrum, soybean plant back timing, and liquid fertilizer carrier recommendations (Source: 2021 Weed Control Guide for Ohio, Indiana and Illinois).
Active Ingredient Trade Name(s) Rate Per Acre Application Timing Winter Annual Weeds Controlled Liquid Fertilizer Carrier Recommendations Soybean Plant Back Restriction
2,4-D Various 1 to 2 pts. Tillering to before jointing Prickly and wild lettuce, mustads, field pennycress, shepherd’s purse, horseweed (marestail), dandelion* The use of a liquid fertilizer as a carrier will increase the risk of crop injury No restriction for early spring applications
Bromoxynil Buctril, Moxy 1 to 2 pts. Emergence to boot stage Mustards, henbit, field pennycress, shepherd’s purse UAN used as a carrier in early spring may increase leaf burn, do not use fertilizer carrier after jointing No restriction for early spring applications
Bromoxynil + pyrasulfotole Huskie 13.5 to 15 oz. After 1-leaf stage up to flag leaf emergence Purple deadnettle, henbit, prickly and wild lettuce, horseweed (marestail), mustards, field pennycress, shepherd’s purse, chickweed Can be applied in a liquid fertilizer solution that does not exceed 50% nitrogen and is not being applied above 30 lb/Acre 4 Months
Bromoxynil + fluroxypyr + 2,4-D Cleansweep D 1 to 1.5 pts. Tillering to before jointing Henbit, horseweed (marestail, mustards, field pennycress, shepherd’s purse, Canada thistle 4 Months
Bromoxynil + fluroxypyr + MCPA Cleansweep M 1 to 1.5 pts. 2-leaf to flag leaf emergence Henbit, horseweed (marestail), mustards, field pennycress, shepherd’s purse, Canada thistle 4 Months
Clopyralid Stinger 0.25 to 0.33 pts. After 2-leaf stage until boot stage Horseweed (marestail), Canada thistle, dandelion*, prickly and wild lettuce 10.5 Months
Clopyralid + 2,4-D Curtail 1 to 2.67 pts. Tillering to jointing Prickly and wild lettuce, mustards, field pennycress, shepherd’s purse, Canada thistle, dandelion*, horseweed (marestail) UAN can be used as a liquid fertilizer carrier 10.5 Months
Dicamba Banvel, Clarity, Sterling Blue, others 0.125 to 0.25 pt. Emergence to before jointing Prickly and wild lettuce, horseweed (marestail), shepherd’s purse, dandelion* Conduct compatibility test as outlined by label prior to application No restriction for early spring applications
Florasulam + MCPA Orion 17 oz. 3-leaf to preboot stage Prickly and wild lettuce, chickweed, field pennycress, shepherd’s purse, mustards 9 Months
Halauxifen-methyl + florasulam Quelex 0.75 oz. 2-leaf to flag leaf emergence Horseweed (marestail), henbit, chickweed, field pennycress, shepherd’s purse, mustards Maximum of 0.25% v/v NIS should be used when applying with a liquid fertilizer 3 Months
MCPA Chiptox, Rhomene, Rhonox, others 1 to 4 pts. Tillering to before jointing Field pennycress, shepherd’s purse. mustards pigweed, prickly lettuce. horseweed (marestail) The use of a liquid fertilizer as a carrier will increase the risk of crop injury No restriction for early spring applications
Mesosulfuron-methyl Osprey 4.75 oz. Emergence to preboot stage Ryegrass, bluegrass, wild oat, field pennycress, wild oat Can be applied in a liquid fertilizer solution that does not exceed 15% nitrogen fertilizer. Maximum of 0.25% v/v NIS should be used when applying with a liquid fertilizer 90 Days
Pinoxaden Axial XL 16.4 oz. 2-leaf to preboot stage Ryegrass Can be applied in a liquid fertilizer solution that does not exceed 50% nitorgen fertilizer. Crop injury may be possible. 120 Days
Pinoxaden + fluroxypyr Axial Star 16.4 oz. 2-leaf to preboot stage Ryegrass Can be applied in a liquid fertilizer solution that does not exceel 50% nitrogen fetilizer. Crop injury may be possible. 4 Months
Propoxycarbaz one-sodium Olympus 0.6 to 0.9 oz. Emergence to before jointing Cheat downy brome, purple deadnettle, horseweed (marestail), mustards, field penny cress, shepherd’s purse Maximum of 0.25% v/v NIS should be used when applying with a liquid fetilizer carrier. Temporary crop injury may occur. 12 Months and 24″ of precipitation
Propoxycarbaz one-sodium + mesosulfuron-methyl Olympus Flex 3 to 3.5 oz. 1-leaf to before jointing Cheat, downy brome, purple deadnettle, horseweed (marestail), mustards, field pennycress, shepherd’s purse, annual gluegrass, ryegrass Maximum of 0.25% v/v NIS should be used when applying with a liquid fertilizer solution. Carrier solutions should not contain more than 15% nitrogen fertilizer 5 Months and 18″ of precipitation
Prosulfuron Peak 0.5 oz. Emergence to second node visible Mustards, field pennycress, prickly and wild lettuce, shepherd’s purse, wild garlic, wild onion Apply with NIS at 1-2 qt./100 gal. when using a liquid fertilizer carrier 10 Months
Pyroxsulam PowerFlex, PowerFlex HL 3.5 oz. 3-leaf to jointing Cheat, downy brome, ryegrass, chickweed, mustards, field pennycress, shepherds purse Can be applied in a liquid fertilizer solution that does not exceel 50% nitrogen and is not being applied above 50 lb/Acre. NIS at 0.25% v/v should be added to solution. 3 Months
Thifensulfuron + tribenuron Harmony Extra TotalSol 0.45 to 0.9 oz. After 2-leaf stage but before flag leaf becomes visible Wild garlic and onion, field pennycress, mustards, chickweed, henbit shepherd’s purse, prickly and wild lettuce, horseweed (marestail), purple deadnettle Include a sulfactant at 0.5-2 pts./100 gal. when applying in a carrier that consist of less than 50% nitrogen fertilizer 45 Days
Tribenuron Express TotalSol 0.25 to 0.5 oz. After 2-leaf stage but before flag leaf becomes visible Chickweed, deadnettle, henbit, wild lettuce, mustards, field pennycress, shepherd’s purse Liquid fertilizer carriers should have 0.06-0.25% v/v NIS added. Temporary crop yellowing and stunting may occur when applied in liquid fertilizer. This injury is occasionally severe, and risk of severe injury may increase under saturated soil conditions. 45 Days
*The highest labeled herbicide rates should be used to achieve control of dandelion plants with spring applications.

 

 

Figure 1. Feeke’s scale of winter wheat stages and herbicide application timings (Source: 2022 Weed Control Guide for Ohio, Indiana and Illinois).

Figure 1. Feeke’s scale of winter wheat stages and herbicide application timings (Source: 2022 Weed Control Guide for Ohio, Indiana and Illinois).

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