Options for Harvest-Aid Treatments for Field Corn

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

There have been several questions regarding options for harvest-aid treatment. A harvest-aid may be a consideration to dry down vegetation prior to harvesting and to reduce foreign matter in the harvested grain. There are a number of things to consider including: what weeds need to be treated; how will harvest-aid be applied; stage of the crop, and size of the weeds.

Be realistic on expectations of these products; while they are herbicides they were developed to control much smaller weeds than the size treated as harvest aids. Most of the products listed below will not kill plants; they are likely to burn off leaves, but not impact lower stems or vines. These products will not affect weed seed production. Reducing leaf material and foreign matter entering the combine should be the goal, not killing the weeds present.

A few more considerations:

  • With the hot temperatures, the risk of drift will increase with these products
  • Spray coverage is important for the contact herbicides (Defol and Gramoxone), so be sure to apply in 20 gpa or higher
  • If morningglory is present, can a combine run through the patches without pulling down the corn?
  • This time of year will favor translocation, so glyphosate is likely to cause more damage to desirable plants
  • Read the product label carefully for all instructions and restrictions

Products labeled:

Defol (sodium chlorate) is labeled for applications 14 days prior to harvest. Defol will dry down plants but it does not have herbicide activity. Dry down is slow; expect at least 14 days for dry down. Control of morningglory can be erratic.

Glyphosate is labeled but must be used with care do to potential injury to desirable vegetation. Apply glyphosate at 35% moisture or less and black layer has formed. Allow 7 days between application and harvest. Refer to the glyphosate label for rates.

Gramoxone Inteon is labeled for broadcast treatments. Application rates are 1.2 to 2 pts/A plus a non-ionic surfactant, and must be applied at least 7 days prior to harvest. Be sure to read the label for all precautions.

Aim is labeled for applications up to 3 days before harvest. Aim will only effect a few weed species and will not dry down grasses.

2,4-D amine is labeled but due to volatility and off-target movement, use of 2,4-D is not recommended. Applications with air temperatures above 85 degrees increases the likelihood of off-target movement. Application timing is after the hard dough or dent stage.