University of Illinois

No. 12/June 12, 1998

Preharvest Treatments for Wheat

The mild fall/winter temperatures coupled with an early spring have allowed many weeds to flourish in wheat fields. With the wheat crop ahead of schedule in many parts of Illinois, producers may be considering planting double-crop soybeans in many wheat stubble fields. Before soybean planting, vegetation existing following wheat harvest should be controlled. A preharvest herbicide application made to the wheat crop can help control existing vegetation prior to wheat harvest and double-crop soybean planting.

Roundup Ultra may be applied using either ground or aerial application equipment. Applications must be made after the hard-dough stage of grain (30 percent or less grain moisture) and at least 7 days prior to harvest. Do not apply more than 1 quart per acre for preharvest applications and do not treat wheat being grown for seed, as a reduction in germination or vigor may occur. Additionally, do not apply to wheat with a legume underseeding.

Some formulations of 2,4-D ester are labeled for preharvest applications in wheat. Use rates vary somewhat by product but usually fall in the range of 1 to 2 pints per acre. Applications should be made after the wheat is in the hard-dough stage, but not to wheat with a legume underseeding.

If a preharvest application of 2,4-D ester is made to the wheat crop, planting soybeans should follow the time intervals set for preplant applications of 2,4-D in no-till systems: 7 days for 1 pint of 2,4-D ester, 30 days for 2 pints. There are no soybean planting restrictions if Roundup Ultra was used as a preharvest treatment.

Marshal McGlamery (mmcglame@uiuc. edu) and Aaron Hager (, Crop Sciences, (217)333-4424