ISSUE 1   May 10, 2007

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MISSING PAGES IN THE 2007 ND WEED GUIDE

Due to printing oversight, some copies of the 2007 Weed Guide are missing pages 17-20 and possibly some pages near the back of the guide. We apologize for this inconvenience. You can get another copy of the guide from your county extension office.

 

HERBICIDE BREAKDOWN IN THE SPRAY TANK

The recent rainstorms may have prevented some from applying mixed herbicides that were ready for application. Questions about degradation and how long the herbicides will last in the tank have been asked. Herbicides are fairly stable in aquatic conditions, if not there would be warnings on the label about minimum time for application after mixing.

How are herbicides broken down? Two methods mainly. The major mechanism of herbicide breakdown is microbial degradation and the other is acid hydrolysis. There are no microbes found in the soil that exist in the spray tank so not much potential for breakdown there. Herbicide degradation through acid hydrolysis affect mainly triazines (atrazine) and some SUs. Most water used for spraying is neutral or slightly alkaline (high pH), not acidic, so not much potential for degradation in the spray tank from hydrolysis. Even if the water was acidic and hydrolysis did occur, it would take some time before enough herbicide was degraded before loss of performance would be detected.

As is usually the case, there is one exception. The "Dim" herbicides, sethoxydim (Poast), clethodim (Select), and tralkoxydim (Achieve) can be broken down by UV sunlight. Herbicide spray solutions that sit in a non-metal spray tank may be degraded by the UV light penetrating the poly material. Sprayers that have stainless steel or metal spray tank would not have this problem.

 

AERIAL APPLICATION OF HERBICIDES

Recent rains have delayed herbicide applications and have created a greater interest in aerial application. It was suggested that we point out a source to quickly determine if a herbicide can be applied aerially. Certain product listings in the North Dakota Weed Guide show the following icon: 

aerial application icon

If the herbicide listing has this symbol it means that no aerial application is allowed. If there is no symbol in the listing then aerial application is allowed. There are only a few herbicides where aerial application is not allowed. The following is a short list of herbicides that are restricted from aerial application:

Far-Go, Buckle, acetochlor, Balance Pro, Permit, Camix, Lumax, Python, linuron, and Crossbow.

Warning: The weed guide does not contain all products registered and many product labels, such as tankmixes, may restrict aerial application. We strongly suggest you review the label if in doubt.

 

ACETOCHLOR LABEL REVISION ALLOWING MORE CROP ROTATIONS

Acetochlor is being re-registered through EPA and, when complete, one of the results will be an increase in the number of crops that can be planted the year following application. Currently, the only crops that can planted the year following acetochlor is corn, soybean, wheat, and sorghum. Many people are asking when the acetochlor (Harness, Surpass, others) labels will be revised to allow crop rotation to most crops grown in North Dakota and Minnesota.

It has not happened yet.

Dow (Surpass) and Monsanto (Harness) registration people anticipate it will be soon. When EPA does approve of these follow crops I will get a message out on <Agdakota> list serve and the next issue of the Crop and Pest Report.

Richard Zollinger
NDSU Extension Weed Specialist
r.zollinger@ndsu.edu


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