One of the most common questions asked of turfgrass specialists is, “what can I use to kill these weeds?” Or, “what should our turf manager be doing for summer weed control?” These questions are especially common at this time of year when summer annual weeds commonly break through depleting preemergence herbicide barriers. At face value this is a simple question, but any correct answer is often far more complex than anticipated by the asker. The first step to some is to correctly identify the weed and the desirable underlying species. After all, only then can an herbicide be selected that will control the weed(s) in question without damaging the underlying turf. While this is absolutely a necessary first step in planning for weed control, in my mind the most important step was overlooked. I believe the first consideration made about controlling weeds should be to determine if the “weed” is actually present at a high enough level to reduce the utility of the turf sward.A few crabgrass plants peeking through an otherwise clean Kentucky bluegrass or tall fescue lawn, athletic field, or golf course playing surface can be frustratingly displeasing to the eye, but are they so detrimental that they need to be controlled? It’s important to remember that the primary function of turf is utility. In addition to preventing even more weeds from establishing in a site, turf stabilizes soil and provides unparalleled wear tolerance for athletics and recreation while producing oxygen, and reducing air temperature compared to synthetic turf, bare soil, or concrete. In my opinion, sparse weed or disease incidence does not interfere with turf utility
in most settings, and attempting complete pest exclusion isn’t worth the cost and risk of treating already stressed turf in midsummer.Herbicides are available to selectively control established grassy and broadleaf weeds, but they are generally less effective on larger plants, requiring higher use rates that increase the risk of injuring desirable species. If sparse weeds are a problem in your turf, consider simply removing them by hand. Provided that present roots/tubers are persistently removed, there is not a more effective, safer weed control strategy. Hand weeding may not be pragmatic on a large scale, especially for weeds that are difficult to remove completely. But, for weeds that are easily removed, hand weeding might not take any more effort than spot treating weeds with herbicide. Furthermore, cursory mechanical weed removal during other tasks will ultimately reduce weed cover with little added effort.
Integrated Turfgrass Management Specialist