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K-State Agronomy eUpdates

Department of Agronomy

Kansas State University

1712 Claflin Rd.

2004 Throckmorton PSC

Manhatan, KS 66506

785-532-6101

agronomy@ksu.edu

Extension Agronomy

Pre-harvest weed control in wheat - Sharpen update

 

Recent rains in western and north central Kansas have delayed wheat harvest and allowed late season weeds to become an increasing harvest problem.  We had an article a couple of weeks ago on pre-harvest weed control options in wheat, but have had several questions since that time regarding the use of Sharpen herbicide as a pre-harvest treatment. Sharpen has been labelled and approved as a pre-harvest treatment in wheat in the U.S. for several years, but still doesn’t have all the export approvals, particularly China.  We made the decision in conjunction with BASF a couple of years ago to not include Sharpen in our recommendations as a pre-harvest treatment as a number of major wheat buyers indicated they would not purchase wheat that had been treated with Sharpen.  However, some additional markets have been approved since that time, and thus, if you want to use Sharpen as a pre-harvest treatment, it is important to visit with your grain buyer about whether they will accept wheat that has been treated with Sharpen. Below is an updated table on pre-harvest treatments for wheat that includes Sharpen.

 

Product and rate/ac

Advantages

Disadvantages

Comments

Aim EC (1 to 2 oz)

Acts quickly, usually within 3 days.

Short waiting interval before harvest – 3 days.

Controls only broadleaf weeds.

Regrowth of weeds may occur after 2-3 weeks or more, depending on the rate used.

Apply after wheat is mature. Always apply with 1% v/v crop oil concentrate in a minimum spray volume of 5 gal/acre for aerial application and 10 gal/acre for ground applications.

Do not apply more than 2 oz of Aim during the growing season.

Dicamba (0.5 pt)

Controls many broadleaf weeds. 

A waiting period of 7 days is required before harvest.

Acts slowly to kill the weeds.

Controls only broadleaf weeds.

High potential for spray drift to susceptible crops.

Apply when the wheat is in the hard dough stage and green color is gone from the nodes of the stem.

Do not use treated wheat for seed unless a germination test results in 95% or greater seed germination.

Glyphosate (1 qt  of 3 lb ae/gal product, or 22 fl oz of Roundup PowerMax or WeatherMax)

Provides control of both grasses and susceptible broadleaf weeds.

Acts slowly. May take up to 2 weeks to completely kill weeds and grasses.

Cannot harvest grain until 7 days after application.  Kochia, pigweeds, and marestail may be resistant.

Apply when wheat is in the hard dough stage (30% or less grain moisture).

Consult label for recommended adjuvants.

Not recommended for wheat being harvested for use as seed.

Metsulfuron (0.1 oz)

Provides control of susceptible broadleaf weeds.

Acts slowly.

Cannot harvest grain until 10 days after application.

Controls only susceptible broadleaf weeds.  Kochia, pigweeds, and marestail may be resistant.

Apply when wheat is in the dough stage.

Always apply with a nonionic surfactant at 0.25 to 0.5% v/v.

Generally recommended in combination with glyphosate or 2,4-D.

Do not use on soils with a pH greater than 7.9.

Weeds growing under limited moisture may not be controlled.

Do not use treated straw for livestock feed.

Sharpen (1 to 2 fl oz)

Quick acting, usually within 3 days.  Short waiting interval before harvest – 3 days.

Primarily effective on susceptible broadleaf weeds.

Apply when wheat is in the hard dough stage and grain contains less than 30% moisture.  Apply with MSO and an ammonium-based adjuvant in a minimum spray volume of 10 gpa by ground or 5 gpa with aerial application. Consult grain buyer to see if they will accept Sharpen treated wheat because of export restrictions.  Treated straw may be grazed or fed to livestock.

2,4-D LVE (1 pt of 4lb/gal product or 2/3 pt 6 lb/gal product)

Provides control of susceptible broadleaf weeds.

Acts slowly. Weak on kochia and wild buckwheat.

Cannot harvest grain until 14 days after application.

Apply when wheat is in the hard dough stage to control large, actively growing broadleaf weeds.

Weeds under drought stress may not be controlled.

Do not use treated straw for livestock feed.

 

 

 

Dallas Peterson, Weed Management Specialist
dpeterso@ksu.edu