Corn harvest has begun in some areas of Tennessee and will likely get started over a more general area toward the end of next week. 

As the combines cut corn they are often leaving behind a very green field of Palmer amaranth. It is not uncommon to find areas of fields where the corn stand is thin due to all the wet weather last spring. 

These areas often have 3’ to 6’ tall Palmer in them just now rolling into flowering. These pigweed need to be destroyed as soon as possible. Allowing them to stand for as little as 7 days will allow them to mature enough to produce viable seed.

Good options to control this late flush of Palmer include tillage and the burndown herbicide Gramoxone (paraquat). If tillage is the option please note it will take aggressive tillage to control >3’ tall Palmer.

In many cases, where residue is needed to be left on the field, tillage followed within a week to 10 days with Gramoxone should provide adequate control.

Some folks last year only sprayed Gramoxone after corn harvest to control existing pigweed and did not add a residual. In most cases that worked well as the dry fall did not allow much new emergence of Palmer. 

I would not count on that this year as soil moisture is quite good in most fields and corn stands are thinner overall than last year.   

Residual herbicides to consider are Valor or Sharpen for fields to go to wheat; Dual Magnum, metribuzin, Sharpen and Valor for fields slated to be planted to soybean; Dual Magnum, metribuzin, simazine and Valor for fields to go back to corn; Dual Magnum and Valor for fields to be planted to cotton. 

Remember if the field is slated to go to wheat that the plant back to wheat after a Valor application is 30 days while Sharpen is labeled pre-plant in wheat.

See more Tennessee crop production information at