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March Weed Control Tips

Dustin Harris and Justin Quetone Moss

Due to abnormally high temperatures throughout the month of February, herbicide applications to warm-season grasses should be carefully considered for March. Before applying a non-selective herbicide such as glyphosate to control winter weeds, it is necessary to verify that the treatment area has not exited dormancy. Many bermudagrass lawns in Oklahoma are already greening up this spring. If so, the application of glyphosate may cause the death of the desirable turfgrass species. Other postemergent herbicides, even selective herbicides, may largely affect the spring green-up timing by a range of a few days to a few weeks. Therefore, it is especially important to monitor the lawn for indications of spring green-up and follow the labeled recommendations before making any herbicide applications to turf stands.

Furthermore, if the weed population is manageable by physical removal, hand-weeding might still be the most practical method of control. However, if the weed population is beyond your threshold for physical removal, a delayed spring green-up would be desired over the competition presented by a mature weed population. Therefore, a product that is labeled for use in the established turf species may be necessary to maintain optimal turfgrass if the weed infestation is severe enough. A simple spot-treatment application may be more practical for small areas or areas with low weed population densities, but a broadcast application may be best suited if the infestation is widespread. However, those two methods of application often require different dilution rates according to labeled recommendations.

Additionally, if your lawn has not received a preemergent herbicide application this year, now is the time to apply before problematic summer annuals begin to germinate. Crabgrasses, foxtail, and sandburs are among the grassy weed species that should not have germinated yet. These are grassy weeds that are best controlled through the use of preemergent herbicides. So, if you’d rather avoid additional mowing throughout the summer or picking sandburs out of yourself and your clothing, be sure that your lawn has been treated appropriately.

As always, it remains important to read product labels in their entirety before making any herbicide application. Additionally, the accurate identification of the weeds you desire to eradicate will aid in selecting the most effective herbicide or combination of herbicides for control of the species present. For additional resources in weed identification and control, contact your respective county extension agent. Additional information on broadleaf weed control can be found in OSU Fact Sheet HLA-6601: Consumer Broadleaf Weed control for Lawns in Oklahoma. 

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