ostemergent herbicides can control existing broadleaf weeds such as dandelion, clover, thistle and chickweed. Postemergent herbicides do not prevent weed seeds from germinating and reinfesting a lawn.
Once the herbicide kills existing weeds, use good cultural practices (proper fertilization, mowing and irrigation) to encourage rapid fill-in of the turf. Otherwise, new weeds will quickly reinfest the bare soil left open by the recently killed weeds. For this reason, use herbicides as only one tool in the total weed control program.
When Do I Apply?
Applications of herbicides intended for postemergent broadleaf weed control kill only those weeds already present when the herbicide is applied. They do not prevent weed seeds from germinating and developing in the lawn at a later date.
For effective control, weeds must be actively growing when the herbicides are applied. Make spring applications from mid-April through early June, and fall applications in September and October. Applications during July and August are strongly discouraged because weed control is often poor and there is an increased risk of causing damage or discoloration to the lawn, as well as to trees, shrubs, flowers and vegetables.
How Do I Apply?
Liquid and granular formulations of herbicides can be equally effective if they are used properly. Do not apply either if rain is expected within 24 hours of application. For best results, do not mow the turf or water for at least 24 hours following application of either granular or liquid products.
Granular herbicides are the most effective if applied to grass that is moist from morning dew, rainfall or irrigation because the granules adhere to the wet surfaces. Application of granular products to dry turf generally controls few weeds. Be careful when applying herbicides near trees, shrubs, flower beds and vegetable gardens. Drift from spray applications or misdirected application of granular products can damage or kill these plants. Tree roots can absorb large amounts of herbicides, so be careful applying any herbicide within a tree's root zone, which extends far beyond the tree's "drip line."
In a mature, older landscape, roots of trees and shrubs often occur throughout the entire lawn area. Do not make more than two herbicide applications per growing season on lawns with trees growing in them. Specifically, dicamba may accumulate in the soil with frequent or extensive use and may result in damage to trees, shrubs or other ornamentals.
Read all label directions before using any pesticide.