• The horseweed in question has either escaped an earlier burndown attempt or was never treated at all.
• In all cases the horseweed is now very large (12 to 18-inches).
• The ryegrass questions have become much more prevalent this year.
Quite a few calls have come in and most can be divided into two main questions.
The most frequent of these is how do I control large horseweed and plant immediately? The next most common is how do I control large ryegrass and plant now?
I will address each of these below:
The horseweed in question has either escaped an earlier burndown attempt or was never treated at all. In all cases the horseweed is now very large (12 to 18-inches).
Unfortunately, there is no one pass answer to this question that will let the field be planted back to soybeans immediately. The most consistent answer is 32 ozs of glyphosate plus 7.5 ozs of Verdict or 1.5 ozs of Sharpen plus 16 ozs of 2,4-D. This treatment has the best chance of success, but the plant back to soybeans is 14 days.
If you want to plant immediately then go with 5 ozs of Verdict or 1 oz of Sharpen plus glyphosate.
Some have asked about tank-mixing Gramoxone in with Verdict or Sharpen? There will be antagonism with this mix and horseweed control will be very poor.
Another option here, particularly if other weeds are also an issue, is Gramoxone plus metribuzin.
Regardless of which way one goes expect at least some horseweed to escape and recover as the soybeans emerge. The best plan on these escapes is either Liberty in LL soybeans or FirstRate plus glyphosate in RR soybeans.
The ryegrass questions have become much more prevalent this year. The only real answer to control large ryegrass at this late date and plant quickly is a clethodim based system. In the Mississippi Delta where the ryegrass is 100 percent resistant to glyphosate they are utilizing 16 ozs of Select Max as their best treatment and still not getting complete control.
In Tennessee, where the ryegrass population is more a mix of moderately to highly resistant to glyphosate a tank-mix of clethodim (Select Max 10 ozs) plus glyphosate (Roundup PowerMax 32 ozs) has proven to be effective.
Both cotton and soybeans can be planted back immediately after a clethodim application.
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