Some love it, others hate it. Common bermudagrass is an aggressive warm-season grass that is well-adapted in areas where cool-season turf species are desirable. It spreads and reproduces by seed production, stolons and rhizomes. Once bermudagrass invades cool-season turf, it is persistent and very difficult to control. Bermudagrass negatively impacts aesthetics of a cool-season rough or fairway by disrupting uniformity due to its course texture and its dormant tan to brown color after frosts.

Photo 1: Tenacity alone bleaches susceptible plants, turning any young and new growth completely white, while Tenacity plus Turflon does not.

Bermudagrass that infests tall fescue or Kentucky bluegrass usually exists in irregular clumps. If left unchecked long enough, it becomes a solid mat with cool-season remnants and winter annual weeds. Bermudagrass is a desirable turfgrass in the South, but it is a great nuisance to cool-season turfgrass managers. Common bermudagrass is the subject of much frustration for those managing cool-season turfgrasses in the transition zone.

Recommended management

Managing for high quality and competitive cool-season turfgrass year round is the first step toward limiting bermudagrass encroachment. Mowing heights above 3 inches for roughs, controlling brown patch and summer patch diseases, and proper cool-season fertility programs are some cultural practices that can limit bermudagrass invasion. However, the stresses of summer often limit cool-season grasses' competitive ability allowing bermudagrass to out-compete the weakened turf.

Probably the most reliable and consistent way to control common bermudagrass is using sequential applications of glyphosate at 5 pounds of active ingredient per acre (lbs ai/A) leading up to fall renovation and reseeding. This method is obviously very time-consuming and labor-intensive, and leaves the area without turf and unusable until establishment from seed or sod.

The selective control program that is most commonly recommended uses the combination of fenoxaprop-P (Acclaim, Bayer ES) and triclopyr (Turflon, Dow AgroSciences) or fluazifop (Ornamec, PBI Gordon) and triclopyr sprayed four times at monthly intervals throughout the bermudagrass growing season. Long-term control with this program varies and depends on many factors. Most often, bermudagrass is only suppressed and managers are forced to deal with significant populations the following season.

New chemistry

Several turfgrass researchers have concluded that mesotrione (Tenacity, Syngenta) controls several problem weeds without injuring tall fescue, perennial ryegrass, or Kentucky bluegrass. Mesotrione has pre- and postemergent activity on several annual weeds. Mesotrione will be the first marketed product to selectively control the perennial weeds nimblewill and bentgrass in cool-season turfgrass. In research at Virginia Tech, two to three sequential applications of mesotrione at 4 fluid ounces per acre (fl oz/A) at three-week intervals is best for controlling nimblewill and bentgrass. While the same program injures bermudagrass, it quickly recovers. This activity indicates potential for additive effects when mixed with other chemistry, potentially improving current bermudagrass control programs.