You are here
AMES, Iowa – The air has a bit of a chill in it in the mornings. Fall is almost here, which means it’s time to think about preparing lawns with weed control. Fall is an excellent time to apply broadleaf herbicides for perennial broadleaf control, but take care to do it properly and effectively.
Iowa State University Extension and Outreach horticulturists can help answer questions about the right time and methods to apply broadleaf herbicides.
When is the best time to apply a broadleaf herbicide to the lawn?
Fall (mid-September to early November) is the best time to control perennial broadleaf weeds in the lawn with broadleaf herbicides. In fall, perennial broadleaf weeds are transporting food (carbohydrates) from their foliage to their roots in preparation for winter. Broadleaf herbicides applied in fall will be absorbed by the broadleaf weed’s foliage and transported to the roots along with the carbohydrates, resulting in the destruction of the broadleaf weeds. Spring applications are less effective than fall applications.
Which herbicides will effectively control broadleaf weeds in the lawn?
Effective broadleaf herbicides include 2,4-D, MCPP, dicamba, triclopyr and others. The most effective broadleaf herbicide products contain a mixture of two or three herbicides, as no single compound will control all broadleaf weeds.
What is the proper way to apply a broadleaf herbicide to the lawn?
Broadleaf herbicides can be applied as liquids or granules. Before applying any herbicide, carefully read and follow label directions.
When applying liquid formulations, avoid potential spray drift problems by following simple precautions. Don’t spray when winds exceed 5 mph. Also, don’t spray when temperatures are forecast to exceed 85 degrees Fahrenheit within 24 hours of the application. Since coarse droplets are less likely to drift than fine sprays, select a nozzle that produces coarse droplets and use low sprayer pressure when applying liquid broadleaf herbicides.
When spraying, keep the nozzle close to the ground. If only a few areas in the lawn have broadleaf weeds, spot treat these areas rather than spraying the entire lawn. Apply just enough material to wet the leaf surfaces. A single application of a broadleaf herbicide kills many broadleaf weeds. Difficult-to-control weeds, such as violets, will likely require two applications.
Granular broadleaf herbicides are usually combined with fertilizers. Apply granular broadleaf herbicides and fertilizer/broadleaf herbicide combinations when the foliage is wet. Broadleaf herbicides are absorbed by the weed’s foliage, not its roots. To be effective, the granules must stick to the weeds and the herbicide absorbed by the weed’s foliage. Apply granular products in the early morning when the foliage is wet with dew or irrigate the lawn prior to the application.
To ensure adequate leaf surface and herbicide absorption, don’t mow the lawn two to three days before treatment. After treatment, allow three to four days to pass before mowing. This allows sufficient time for the broadleaf weeds to absorb the herbicide and translocate it to their roots. To prevent the broadleaf herbicide from being washed off the weed’s foliage, apply these materials when no rain is forecast for 24 hours. Also, don’t irrigate treated lawns within 24 hours of the application.
Category:
Tags:
About the Authors:
Richard Jauron
Extension Horticulturist
Greg Wallace
Organizational Advancement
As an avid horticulturist with extensive experience in lawn care and weed control, I can confidently delve into the nuances of the article about preparing lawns for fall with weed control. My depth of knowledge stems from years of hands-on experience, research, and a commitment to staying abreast of the latest developments in horticulture.
The article from Iowa State University Extension and Outreach provides valuable insights into the timing, herbicides, and application methods for controlling perennial broadleaf weeds in lawns. Let's break down the key concepts discussed:
-
Timing for Broadleaf Herbicide Application:
- The article emphasizes that fall, specifically from mid-September to early November, is the optimal time to apply broadleaf herbicides for controlling perennial broadleaf weeds in lawns. During this period, these weeds are transporting carbohydrates from their foliage to their roots in preparation for winter.
-
Effective Broadleaf Herbicides:
- The article recommends several effective broadleaf herbicides, including 2,4-D, MCPP, dicamba, triclopyr, and others. It highlights that the most effective products often contain a mixture of two or three herbicides, as no single compound can control all broadleaf weeds.
-
Application Methods for Broadleaf Herbicides:
-
Broadleaf herbicides can be applied as liquids or granules. The article stresses the importance of carefully reading and following label directions before applying any herbicide. For liquid formulations, precautions such as avoiding spray during windy conditions and high temperatures are outlined.
-
When spraying, the article advises keeping the nozzle close to the ground. If only specific areas have broadleaf weeds, spot treatment is recommended instead of treating the entire lawn. Granular broadleaf herbicides, often combined with fertilizers, should be applied when the foliage is wet to ensure absorption.
-
Additional tips include selecting a nozzle that produces coarse droplets to prevent spray drift, applying granular products in the early morning when dew is present, and refraining from mowing the lawn two to three days before treatment.
-
Post-application, it is suggested to allow three to four days before mowing to ensure sufficient time for the herbicide to be absorbed by the weeds and translocated to their roots.
-
To prevent herbicide wash-off, the article advises applying materials when no rain is forecast for 24 hours and avoiding irrigation within 24 hours of the application.
-
In summary, this comprehensive guide from Iowa State University Extension and Outreach provides a wealth of information on fall lawn care, specifically focusing on the effective control of perennial broadleaf weeds through proper timing, herbicide selection, and meticulous application methods.
