Preemergence herbicides are the foundation of herbicide-based weed management systems, and effective use of these products is essential to protect crop yields and reduce selection pressure for herbicide resistant weeds. In a perfect world, applying preemergence herbicides immediately after planting would provide the greatest likelihood of maximum performance, but equipment and labor availability limit many farms from using this approach. This article will provide a brief overview of the pros and cons of different application strategies.
Early preplant: Applications made more than 7 to 10 days prior to planting. |
|
Pros |
Cons |
|
|
Preplant/Preemergence: Applications made within a week before or after planting. |
|
Pros |
Cons |
|
|
Delayed preemergence: Applications made more than a week after planting. |
|
Pros |
Cons |
|
|
Herbicide resistant weeds have limited our ability to ‘rescue’ fields when weather delays preemergence applications following planting. Thus, consider how you can ensure that all acres are protected with appropriate preemergence herbicide applications when prolonged wet periods or other factors interfere with field operations.

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on April 9, 2020. The information contained within may not be the most current and accurate depending on when it is accessed.