Every year as we watch the Super Bowl, especially the playing conditions of the field, it should serve as a reminder that to have weed control success with pre-emergence herbicides on our lawns this summer, the time is now to get these herbicides purchased and applied. TIMING, RATE, UNIFORM COVERAGE, and ACTIVATION are the keys to effective pre-emergence herbicide weed control.
These herbicides must be applied prior to weed seed germination. Seeds of weeds, such as crabgrass, will germinate when soil temperatures reach around 58 degrees. And even though it may feel very cold now, it only takes a few sunny days to raise the soil temperature to this level. Therefore, you need to consider getting your pre-emergence herbicide on to your lawn very soon. A couple of weeks early is much better than a day late missing those early germinating weeds.
The herbicide label will provide a list of the weed species, the active ingredient it will control, and at what rate. If there are several weed species that you are targeting, use a rate that controls the most difficult weed while staying within recommended rates labeled for your specific turf species.
Pre-emergence herbicides create a thin weed control barrier on the soil surface. This barrier must provide complete coverage at a uniform rate to prevent any voids that would allow weed escapes. Liquid or granular application equipment should be accurately calibrated prior to making an application to ensure proper rates and coverage.
Finally, once the herbicide is applied it must be activated. This will require approximately one-half inch of rainfall or irrigation shortly after application to move the herbicide down through the leaf canopy to form the thin herbicide barrier at the soil surface. As with any pesticide, you should always READ THE LABEL carefully and completely before applying.
Published February 5, 2007
Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. wwells@ext.msstate.edu
