POST Herbicide Application Reminders

The following are general recommendations for POST herbicide applications for corn and soybean:

Scout fields to accurately determine the growth stage of the crop and the degree of variability that may exist across the field. Weed species that are present and their height should also be recorded. Always follow crop size limitations per product label in order to prevent crop injury and facilitate good weed control.

The rate for the field should be determined by the largest or most difficult to control weed, not the most prevalent. For example, if the field has predominantly 3- to 4-inch velvetleaf, but also contains numerous 12-inch lambsquarters, the recommended rate should target the height of the lambsquarters.

Avoid making POST applications during abnormally cool or dry, droughty weather since weeds may not be actively growing under these conditions. Delaying application until weeds resume active growth may result in improved control. Herbicide penetration and activity are usually improved when the temperature and relative humidity is high, but the potential for crop injury may also increase under these conditions.

The use of an adjuvant is often recommended on product labels to improve spray coverage and herbicide uptake. Weed control may improve with the use of adjuvants, but crop injury may increase. Always follow product label instructions regarding the use of additives. Use the most restrictive label directions when considering tank-mix combinations.

Reminders for POST applications of Roundup® brand agricultural herbicides to corn or soybean with a Roundup Ready® technology and Roundup Ready 2 Xtend® soybean

: Except for preharvest applications, DO NOT apply after R2 (full flowering) growth stage in soybean with a Roundup Ready technology or Roundup Ready 2 Xtend soybean, or after V8 (8 visible leaf collars) growth stage or 30-inch corn with a Roundup Ready technology (without drop nozzles).


Reminders for POST applications of XtendiMax® Herbicide with VaporGrip® Technology to Roundup Ready 2 Xtend soybean:

  • XtendiMax with VaporGrip Technology has specific requirements for nozzles/operating pressures, adjuvants, DRAs, and other herbicides. Visit for the most up-to-date information.
  • Visit for regional weed management recommendations.
  • XtendiMax with VaporGrip Technology can be applied up to and including R1 (beginning bloom) growth stage in Roundup Ready 2 Xtend soybean.
  • The in-crop application rate is 22 fl oz/acre for crops with Roundup Ready 2 Xtend Technology (two in-crop applications are allowed per year).
  • For best results, apply when weeds are less than 4 inches tall.
  • When tank-mixing with XtendiMax® Herbicide with VaporGrip® Technology, the labeled glyphosate options and some other tank-mix partners will require the use of specific approved drift reducing adjuvants (DRAs).
  • Do not use ammonium sulfate or ammonium-based additives with XtendiMax with VaporGrip Technology.
  • The RRXtend Spray App is a free, farmer- and applicator-focused digital tool that provides location-specific weather forecasts, digital record-keeping capabilities, and educational resources related to the Roundup Ready® Xtend Crop System. The forecasts provide field-level, location-specific hourly forecasts including wind speed and direction, inversion risk forecast to show the probability (by percentage) of an inversion occurring at a particular location and forecast hour, temperature, and relative humidity. Go to for further information. 180525130402