Bermuda Control Advances By John Willis and Shawn Askew leaves the area without turf and unusable until establish- ome love it, others hate it. Common bermudagrass is ment from seed or sod. an aggressive warm-season grass that is well-adapted The selective control program that is most commonly Sin areas where cool-season turf species are desirable. recommended uses the combination of fenoxaprop-P It spreads and reproduces by seed production, stolons and (Acclaim, Bayer ES) and triclopyr (Turflon, Dow AgroSci- rhizomes. Once bermudagrass invades cool-season turf, it is ences) or fluazifop (Ornamec, PBI Gordon) and triclopyr persistent and very difficult to control. Bermudagrass nega- sprayed four times at monthly intervals throughout the tively impacts aesthetics of a cool-season rough or fairway by bermudagrass growing season. Long-term control with this disrupting uniformity due to its course texture and its dor- program varies and depends on many factors. Most often, mant tan to brown color after frosts. bermudagrass is only suppressed and managers are forced to Bermudagrass that infests tall fescue or Kentucky blue- deal with significant populations the following season. grass usually exists in irregular clumps. If left unchecked long enough, it becomes a solid mat with cool-season New chemistry remnants and winter annual weeds. Bermudagrass is a Several turfgrass researchers have concluded that mesotri- desirable turfgrass in the South, but it is a great nuisance one (Tenacity, Syngenta) controls several problem weeds to cool-season turfgrass managers. Common bermudag- without injuring tall fescue, perennial ryegrass, or Kentucky rass is the subject of much frustration for those managing bluegrass. Mesotrione has pre- and postemergent activity on cool-season turfgrasses in the transition zone. several annual weeds. Mesotrione will be the first marketed product to selectively control the perennial weeds nimblewill Recommended management and bentgrass in cool-season turfgrass. In research at Virginia Managing for high quality and competitive cool-sea- Tech, two to three sequential applications of mesotrione at son turfgrass year round is the first step toward limiting 4 fluid ounces per acre (fl oz/A) at three-week intervals is bermudagrass encroachment. Mowing heights above 3 best for controlling nimblewill and bentgrass. While the same inches for roughs, controlling brown patch and summer program injures bermudagrass, it quickly recovers. This activ- patch diseases, and proper cool-season fertility programs ity indicates potential for additive effects when mixed with are some cultural practices that can limit bermudagrass other chemistry, potentially improving current bermudag- invasion. However, the stresses of summer often limit rass control programs. cool-season grasses' competitive ability allowing bermu- dagrass to out-compete the weakened turf. Our results Probably the most reliable and consistent way to control Our application schemes that avoided summer appli- common bermudagrass is using sequential applications of cations on stressed turf seemed to avoid injury to both glyphosate at 5 pounds of active ingredient per acre (lbs ai/ Kentucky bluegrass and perennial ryegrass. Perennial A) leading up to fall renovation and reseeding. This method ryegrass was more sensitive to mesotrione containing is obviously very time-consuming and labor-intensive, and treatments than Kentucky bluegrass. We did note more severe injury during drought conditions. Even though PHOTO 1 the most severe injury was at levels slightly above 30 percent — the line we draw as "acceptable injury" — the turf was only injured for about one week and completely recovered by three weeks after treatment. For all herbicide treatments, applying six total applications (three spring and three fall) controlled bermudagrass better than four herbicide treatments (two spring and two fall). Of the three herbicides that we included in combinations, no Tenacity plus single product seemed to stand out as the most important to Tenacity Turflon include in the tank mixtures. Of the two-way tank-mixes, Tenacity alone bleaches susceptible plants, turning any fenoxaprop-P plus triclopyr controlled bermudagrass slightly young and new growth completely white, while Tenacity better than mesotrione plus triclopyr, but both treatments plus Turflon does not. Continued on page 84 Continued from page 80 istic effect on bermudagrass and had higher turf were very effective. color evaluations than mesotrione alone. Further The best treatment was fenoxaprop-P plus research with this combination found that there triclopyr plus mesotrione. This combination were similar effects toward several other species reduced bermudagrass cover from 71 percent including nimblewill, crabgrass, bentgrass, and when the study started to 2 percent when evalu- several broadleaf species. Additionally, mesotri- ated mid-summer in the next season. The major- one plus triclopyr is outstanding for general weed ity of the plots treated with this combination control. The combinations control perennial were completely free of bermudagrass. No previ- broadleaf weeds that mesotrione alone does not ous selective bermudagrass control program has control well like white clover, broadleaf plantain, reduced bermudagrass populations this much in and wild violet while controlling nimblewill, bent- one growing season. Although this strategy does grass, and crabgrass when applied in sequence. not affect bermudagrass in summer for about So if you chose to use mesotrione and triclopyr in two months, we speculate that spring applica- programs for bermudagrass, nimblewill or bent- tions provide enough initial suppression to limit grass control, you will more than likely not have active growth through most of the summer, and other weeds to worry about in the treated areas. then fall applications completely deplete energy reserves in rhizomes and stolons. Bermudagrass John Willis is a research associate and Ph.D. can- then succumbs to the combination of herbicide didate in turfgrass weed science at Virginia Tech in Blacksburg, Va. effects and winter kill. There are disadvantages to this program. One Shawn Askew is associate professor of turfgrass is cost. Another problem is that the 4 oz/A rate weed science in the department of plant pathol- of mesotrione and 32 oz/A rate of Turflon Ester ogy at Virginia Tech. He is also Virginia's extension (triclopyr) that we used would exceed annual specialist for turfgrass weeds. For more informa- use rates if the products are broadcast applied to tion, visit his web site at www.turfweeds.net. the target area. Obviously, being a six-applica- tion program, simply treating six times will not be cheap or easy. Data suggest that stretching TURFGRASS TRENDS

application intervals or missing applications will SECTION STAFF greatly reduce the effectiveness of these treat- Managing Editor Graphic Designer JOHN DEERE Curt Harter Kristen Morabito ments. So sticking to the timings outlined above 440-238-4556; 440-238-4116 (fax) 216-706-3776; 216-706-3712 (fax QUICK TIP is a necessity. These treatments would be more curt@curtharler. com [email protected] economical and likely less injurious when spot Golfdom Staff Contact With spring just applied instead of broadcast applied. Our future David Frabotta 216-706-3758; 216-706-3712 (fax) around the corner, efforts will combine more herbicides to avoid it's time to think [email protected] exceeding annual use rates. We will target the about the inevitable herbicides with least effects on turf for summer nuisance: weeds. INDUSTRY ADVISORS treatments and more aggressive herbicides for To assist in preven- Jerry Quinn Scott Welge tion, use a selective spring and fall treatments. We will also test tank John Deere Bayer Environmental Science pre-emergent her- mixtures of even more than three products in an Chris Derrick Carmen Magro bicide for control of attempt to find the holy grail of single treatment, Agrium Advanced Technologies Fioratine annual grasses and selective bermudagrass control. broadleaf weeds in Mesotrione is a new herbicide to turfgrass EDITORIAL REVIEW BOARD turf and ornamen- Dr. Rick Brandenburg Dr. Eric Nelson markets. Applications of mesotrione produce N.C. State University Cornell University tals. For more infor- extremely bleached bermudagrass, essentially Dr. Vic Cibeault Dr. A.J. Powell mation on weed University of California University of Kentucky turning bermudagrass white, significantly reduc- control, contact Dr. Garald Horst Dr. Eliot C. Roberts ing turf color ratings for plots treated with mesot- University of Nebraska Rosehall Associates your John Deere Dr. Richard Hull Dr. Pat Vittum Golf agronomic rione. This is because mesotrione inhibits carot- University of Rhode Island University of Massachusetts sales representa- enoid biosynthesis in susceptible plants. Another tive, or visit www. interesting finding was that mesotrione plus tri- CONTACT US: johndeere.com clopyr combinations did not have this character- Web site: www.turfgrasstrends.com Reprints: TurfgrassTrends@reprintbuyer. com