By Dr. Jack Fry
Crabgrass is now becoming quite visible. If you didn’t apply a preemergence herbicide, or had some crabgrass emerge even where it was applied, now is the time to consider postemergence control. If a preemergence herbicide was applied, but you’re still seeing crabgrass, there may have been variability in uniformity of delivery over the area to which it was applied. If new sod was laid recently, it’s common for crabgrass to emerge through the seams. Control is easier when plants are young, for they are rapidly growing and have a thinner leaf cuticle. Make sure the crabgrass plant isn’t under stress before you apply the herbicide; rainfall or irrigation on the area within a few days prior to application can help ensure the herbicide is absorbed and translocated. Dr. Hoyle wrote a nice summary of best approaches to postemergence crabgrass control here: https://blogs.k-state.edu/turf/postemergent-crabgrass-control
In addition, consider purchasing Turf Weed Control for Professionals, which was developed by cooperatively by numerous universities in the Midwest, including K-State. It can be purchased as a hard copy or a PDF download here: https://mdc.itap.purdue.edu/item.asp?Item_Number=TURF-100
