The Cannon County UT Extension Office has released information about the management of Palmer Amaranth in non activated pre herbicide situations As anticipated the dry conditions that we experienced last week and that continue through today are not activating pre applied herbicides. Reports of Palmer amaranth already 1 to 2” tall with emerging crops appears to be common. How to proceed from here on weed management depends upon the crop as well as the herbicide tolerant trait in the crop.In RR or conventional soybeans a number of folks are weighing how to manage the emerged Palmer amaranth. The uncertainty comes from the fact that the PRE applied herbicide is still present and will activate with a rain. If the PRE applied herbicide is a Valor or Authority based product and Prefix is used now to control the Palmer some soybean injury would be likely if Prefix and Valor or Authority activate all at once. With this in mind it would be best to try to remove the existing Palmer amaranth with Ultra Blazer or Cobra and come back later with Prefix
In LL soybeans Liberty can control Palmer amaranth even up to 4” tall in one shot. Remember for best results to apply the Liberty from midmorning until about an hour before sundown. For larger Palmer amaranth a sequential application of Liberty applied about 7 days later may be needed for complete control.
There are some good options in corn for this problem. All the common premixes like Halex GT, Capreno and RealmQtankmixed with atrazine will control Palmer. Once corn gets about 12” tall consider using 4 ozs/A of Status in place of atrazine. Our studies over the years would indicate that at least two modes of action effective on Palmer are needed to control it in corn once Palmer gets 6” tall. For more information please contact Bruce Steelman at the County Extension Office at 615-563-2554
