Pre-Harvest Grain Sorghum Application of a Roundup® Brand Agricultural Herbicide

Benefits of a Pre-Harvest Application

Roundup brand agricultural herbicides (Roundup PowerMAX Roundup PowerMAX® II, and Roundup WeatherMAX® are registered for pre-harvest use to kill weeds and terminate grain sorghum plants. Benefits of a pre-harvest application can include earlier harvest timing, reduced grain moisture at harvest, increased harvest efficiency due to less green matter, late-season weed control, and reduced late-season water uptake, which can result in more soil moisture available for the next crop.

Pre-Harvest Application Recommendations for Roundup Brand Agricultural Herbicides in Grain Sorghum


When—Apply a Roundup brand agricultural herbicide when grain sorghum is at 30% moisture or less. Physiological maturity occurs when a “black layer65533;? forms at the base of grain berries. Tiller heads may mature later than primary heads.

Rate—Apply 22 to 32 fl oz/acre. Do not apply more than 44 fl oz/acre. By ground application equipment at 5 to 10 gal/acre, and by aerial application at 3 to 5 gal/acre.13;10;Add ammonium sulfate (AMS) at 8.5 to 17 lbs per 100 gal of spray solution.

Restrictions—Allow a minimum of 7 days between application and harvest of grain sorghum.

Application Restrictions

Roundup brand agricultural herbicides should not be used pre-harvest on sorghum grown for seed as a reduction in germination or vigor may occur. After an application of a Roundup brand agricultural herbicide, sorghum should not be harvested for a minimum of 7 days and it may take from 2 to 3 weeks for the herbicide to completely kill the sorghum plant. Making a pre-harvest application too early may reduce grain quality and yield potential.

When applying a Roundup brand agricultural herbicide pre-harvest, if grain sorghum is drought-stressed, diseased, or lush due to irrigation, it is recommended to increase the application towards the higher end of the labeled herbicide rate and add a full rate of AMS (17 lbs/100 gal of spray solution).

Grain Sorghum Infected with Charcoal Rot

Grain sorghum plants infected with charcoal rot will have stalk degradation, and should not receive a pre-harvest application of a Roundup brand agricultural herbicide. Plants infected with charcoal rot are more likely to lodge after application, reducing harvest efficiency, grain quality, and yield potential.