Increasing the Odds for Successful Weed Control

February 16, 2018 by Keith Reed

It is anyone’s guess what this spring and summer is going to look like, but based on where we stand right now and what the short range forecast models are showing, it looks like we may have a very dry spring ahead of us.

Drought conditions can have an adverse effect on herbicide control activity in at least two ways.  First we will talk about the winter annual weeds such as chickweed, henbit and annual bluegrass that have already come up and are waiting patiently for the weather to warm.  These are the weeds that give so many people spring mowing headaches. 

Ordinarily, these weeds can be easily controlled in February and March with the proper application of herbicide.  However, these herbicides depend on some uptake and movement of the product through the plant to be effective.  For this to happen, there needs to be enough moisture present for the plant to be growing.  (Even if it is a very slow growth).  If you will be making a winter weed control application this year, I suggest one thorough irrigation a few days before you plan to spray to make sure these weeds are growing well enough to take up the herbicide.

The other issue, and one that can really cause grief during late summer, is the premature breakdown of crabgrass preemergent herbicide.  This may sound a little odd so perhaps it might be helpful to have a basic review of how these products work.

Preemergent herbicides, by definition, must be applied and activated before the target weeds germinate.  The key word here is activated.  Ordinary spring rains usually take care of this for us.  These products are designed to create a thin layer of protection right on the soil surface that kills the weed seeds as they try to germinate.  This layer relies on irrigation or rainfall to wash the herbicide off the surface and onto the soil where it spreads evenly across the soil surface.  This holds true for both granular products, and sprayable liquids.

There are many crabgrass control products on the market and they can vary greatly on the length of time they can remain on the soil surface before being irrigated.  The label should provide this information.  If you are having your lawn treated by a professional service, be sure and ask them how long you can wait before needing to water it in. 

After having said all that, let’s hope none of this information will be needed this spring!

For more information on this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office.  Keith can be reached via email at, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.

Oklahoma State University, in compliance with Title VI and VII of the Civil Rights Act of 1964, Executive Order 11246 as amended, Title IX of the Education Amendments of 1972, Americans with Disabilities Act of 1990, and other federal laws and regulations, does not discriminate on the basis of race, color, national origin, gender, age, religion, disability, or status as a veteran in any of its policies



Document Actions