January 11, 2007

4 Min Read

It has been an interesting week. I have participated in two meetings of the Arkansas State Plant Board pesticide committee dealing with herbicide drift issues.

One of the meetings dealt with 2,4-D issues and the other with glyphosate issues. Both meetings resulted in recommendations for significant changes to be considered by the full board in an upcoming meeting.

Anytime there are changes, not everyone is going to be happy. As I have said before, all of us have good ideas on how to fix problems as they affect us individually. The difficulty is finding solutions that are fair and equitable for everyone involved.

Unfortunately, the actions of a few result in changes that affect everyone.

With 2,4-D, the proposed changes will result in a stop use of aerial and ground applications of 2,4-D between April 15 and Sept. 15 in the counties along Crowley’s Ridge from Clay County to Phillips County.

It is the general consensus of weed science experts that the widespread 2,4-D symptoms on cotton on the east side of the ridge from Cross to Clay counties in 2006 was the result of applications made in temperature inversions on the west side.

In other years the symptoms have resulted from 2,4-D applied in other areas — sometimes in a neighboring state.

This regulation affects a lot of rice farmers on the west side of the ridge that should be able to safely apply 2,4-D. In a lot of cases it is 10 to 20 miles from a cotton field to the closest rice field. It is impossible to drift the material that far.

The only way to move it that far is hang it up in an inversion. Inversions occur in still air.

The old school thinking is you apply herbicides with the potential to cause problems at long distances right before daylight or just before dark when the wind is not blowing. It is obvious there remains the mentality among some to “get the stuff out before the wind gets up.”

We have since learned that is precisely the wrong thing to do. Those type herbicides should not be applied until there is a 2 to 3 degree temperature change and a 2 to 3 mph wind blowing away from the susceptible crop.

In the real world in the summer, when you wait for the wind to get up to 2 to 3 mph, it often isn’t long before it is 10 mph. That makes it difficult to get a lot of 2,4-D sprayed in the narrow application window on rice.

When an application is made in still air because you know the wind is going to be blowing toward a susceptible crop when it gets up later, a herbicide like 2,4-D simply should not be applied. It could wind up affecting cotton at far greater distances than if it had been applied with a wind blowing in that direction.

I am not saying it should be applied with the wind blowing toward cotton either. The problem with the 2,4-D issue last year was it was the most widespread I have seen in my career, and it was impossible to track any of it back to a source.

If the regulations are adopted as proposed, there is a provision for a farmer in the affected area to obtain an exemption for 2,4-D to be applied essentially under the direct supervision of a State Plant Board representative.

My guess is most rice farmers will simply go to alternative herbicides. However, some farmers at the meeting expressed concerns that alternatives such as Grandstand had not worked well for them and they would seek the exemption.

When 2,4-D can not be used in a weed control program, propanil plus Grandstand can be a good substitute at midseason. However, I also suggest giving more attention to broadleaf control earlier in the season. Usually a tank mix partner can be added to the grass control program to get all of the early emerging broadleaf weeds out of the picture. I will write more about that as we get closer to that time of year.

While the proposed changes will not please everyone, and they may not even be completely fair to everyone, something had to be done and the committee did the best it could after seeking as much input as possible.

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