Harvest Aid in Wheat

Chad Lee, Travis Legleiter and Carrie Knott, University of Kentucky

The cool, cloudy and rainy temperatures this spring delayed wheat development across much of Kentucky. The wet weather recently has many thinking about adding a harvest aid to their fields. Although much of the wheat is likely back to a ‘normal’ development stage due to recent record-breaking high temperatures, many producers may already be considering harvest aids in wheat.

Harvest aids remove weeds that complicate harvest and potentially stain wheat grains. Harvest aids should not be used to help a crop dry down faster.

Several products are labeled as harvest aids. A subset of those products is listed in Table 1. They are labeled for the “hard dough stage” (actually hard kernel stage or Feekes 11.3) when seeds are at 30% moisture or less. This stage is physiological maturity when the seed development is complete. Applying the harvest before physiological maturity often reduces yield and test weight, especially in soft red winter wheat. Earlier application of glyphosate has less effect on yield of spring wheats grown in Canada and North Dakota. Some growers may be reading articles that promote earlier timings of application and those early timings apply to the spring wheats, not to soft red winter wheat grown in this region.

Most products labeled for harvest aid have harvest intervals of either 7 or 14 days. This means that once the product is applied, the crop cannot be harvested until at least 7 or 14 days after the product is applied. Some products have restrictions on feeding straw to livestock while others allow feeding straw to livestock. Some products do not allow applications on fields being grown for seed production.

If you are considering a harvest aid application in wheat, read the label of the products being considered. Follow the label. Again, the harvest aid application is best suited to removing problematic weeds. Applying a harvest aid to speed up drydown will likely reduce yield and test weight. 

There are numerous products containing glyphosate. Read the label of that product for specific directions on harvest aids. The ones we found all had the same growth stage for application (less than 30% grain moisture). Those labels had variances in grazing restrictions and the use rates differed.

Referenced Research Papers:  

Darwent, A.L., et al. 1993. Effect of Preharvest Applications of Glyphosate on the Drying, Yield and Quality of Wheat. Canadian J. of Plant Science.

Nelson, et al. 2011. Harvest Application Timing Effects Wheat and Relay Intercropped Soybean. Agronomy Journal. 103: 851-855.

Yenish, J.P. and F.L. Young. 2000. Effect of Preharvest Glyphosate Application on Seed and Seedling Quality of Spring Wheat (Triticum aestivum). Weed Technol. 14: 212-217.