Fall is Prime Time For Broadleaf Weed Control
by Don Janssen, Extension Educator
The best time to control perennial broadleaf weeds in the lawn with broadleaf herbicides is fall (mid-September through October). In fall, perennial broadleaf weeds are actively translocating carbohydrates to their roots. Broadleaf herbicides applied to the weeds will be absorbed by the foliage and translocated to the plant's roots along with the carbohydrates. This usually results in the death of the broadleaf weeds.
Broadleaf herbicides can be applied as liquids or granules. When applying liquid formulations, potential spray drift problems can be avoided by following simple precautions. Don't spray when winds exceed 5 mph. Also, don't spray when temperatures are forecast to exceed 85 degrees F within 24 hours of the application. Since coarse droplets are less likely to drift than fine sprays, select nozzles that produce coarse droplets and use low sprayer pressure when applying liquid broadleaf herbicides. If only a few areas in the lawn have broadleaf weed problems, spot treat these areas rather than spraying the entire lawn. Apply just enough material to wet the leaf surfaces.
Granular broadleaf herbicides are often combined with fertilizers. Apply granular broadleaf herbicides and fertilizer-broadleaf herbicide combinations when the weed foliage is wet. Wet leaf surfaces allow the granules to stick to the foliage, permitting herbicide uptake. Apply granular products in the early morning when the foliage is wet with dew or irrigate the lawn prior to the application.
To insure adequate leaf surface and herbicide absorption, don't mow the lawn 2 or 3 days before treatment. After treatment, allow another 2 or 3 days to pass before mowing. This allows sufficient time for the herbicide to be translocated to the plant's roots. To prevent the broadleaf herbicide from being washed off the plant'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.
Broadleaf herbicides are important tools in controlling weeds in the lawn. However, good cultural practices are also important. Proper mowing, fertilization, and other sound management practices should help establish a thick, healthy lawn. A dense stand of grass provides few opportunities for unwanted weeds. Good cultural practices, along with an occasional application of a broadleaf herbicide, should effectively control most broadleaf weeds in the lawn.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office