Controlling Large Palmer Amaranth in Tall Corn

Author: Larry Steckel, Extension Weed Specialist Comments Off on Controlling Large Palmer Amaranth in Tall Corn

Just by driving through Tennessee there is no doubt we are a corn state this year.  It seems like everywhere you look there is a field of corn. Much of this corn will get the “layby” application applied over the next 10 days.  With the warm temperatures of the last few days the corn will quickly grow past the stage that herbicides like atrazine can be applied.  Please refer to the blog posted Apr 16 for specific maturity cut offs for various corn herbicides.

There is some good size Palmer amaranth up in the corn in some fields.

Palmer amaranth 6" in V 7 corn

The common question is how large a pigweed will the popular layby premixes Halex GT, Capreno or Realm Q control?  All three of those herbicides are a bleaching based herbicide premix.  The bleaching herbicide in Capreno is Laudis. The bleaching herbicide in Halex GT and Realm Q is Callisto.  Those herbicides can effectively control Palmer up to 6” tall depending upon rate. When Palmer becomes larger than that a tankmix partner is needed for consistent control. The most commonly used tankmix partner is atrazine.  When atrazine is tankmixed in with one of those herbicide premixes mentioned above considerably larger Palmer can be controlled.  However, atrazine can only be used on corn up to 12” tall.  What about large Palmer in corn that is taller than 12”? 

One good option that just recieved a label is Halex GT + Status in tall (24″) corn.  Other options would be Liberty tankmixed with Capreno in Liberty Link corn.  Liberty at 22 ozs/A can be tankmixed in with Capreno on corn up to 24” tall.  In our research we have seen Palmer as large as 12” controlled with a tankmixture of Liberty + Capreno.  The Callisto-based premixes cannot be tankmixed safely with anything other than atrazine on large Palmer.  A sequential application of Status applied 7 to 10 days after the Callisto-based premix should finish off any large Palmer that escape the Callisto.  Status may be applied at rates as high as 5 to 10 oz/A on corn from 4 to 36” tall.

There are some other options that do not include the premixes mentioned above that should be effective on large Palmer in tall corn.   Impact/Armezon + Status would be a good choice on large corn (36″). Other options include Callisto at 3 oz/a or Laudis at 2 to 3 oz/A  plus Liberty at 22 oz/A would be an effective option on Palmer over 10” tall.  Another effective option on large Palmer would be a tankmix of Status and Liberty.  All of these combinations can be applied to corn up to 24” tall. We are leaning so hard on Liberty in soybean and cotton now, that I am hesitant to recomend them in corn for resistance managment.  However, they are labeled and will work.

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