Roundup Ready Creeping Bent has Application Trial

Research explores nondestructive transitional methods

Roundup Ready creeping bentgrass (Agrostis stolonifera) (RRCB) is a product of The Scotts Co. and Monsanto that is similar to Roundup Ready agricultural crops that have been commercially available for several years. However, if Roundup Ready creeping bentgrass is approved and receives federal registration, it will be the first genetically modified turfgrass. Recently, much research has been initiated to investigate various applications as well as potential areas of concern associated with RRCB.

Upon the registration and approval of RRCB, golf course superintendents would have the opportunity to incorporate RRCB into new golf course construction or renovate existing playing surfaces. Once RRCB is established, superintendents would be allowed to incorporate Roundup into their weed-control management plans.

Quick Tip

Although weed-control programs in RRCB should not rely solely on Roundup, it certainly would be a valuable tool in managing hard-to-control perennial and annual weeds. Specifically, control options are limited with annual bluegrass (Poa annua) in creeping bentgrass and typically result in annual bluegrass suppression whereas Roundup has great activity on both annual and perennial biotypes of annual bluegrass. Another scenario where RRCB would be beneficial is in creeping bentgrass putting greens with bermudagrass surrounds.

Bermudagrass encroachment into these greens has been fought by superintendents with barrier and edging systems and herbicides for a number of years; however, if the greens were renovated with RRCB, the superintendent would be allowed to control bermudagrass selectively without adversely affecting the bentgrass. Possible areas of concern with the use of RRCB include outcrossing with other Agrostis species, movement of transgenic seed into nontransgenic areas, and treatment of irregular-shaped areas that are bordered by nontransgenic turfgrass species.

Research trials were initiated to determine if an existing Penncross bentgrass fairway could be renovated with RRCB utilizing nondestructive seedbed preparation in combination with sublethal Roundup applications. The intent was to prepare a seedbed conducive for RRCB establishment without disrupting play. Additionally, with sublethal rates of Roundup, it was hypothesized the growth of the existing Penncross bentgrass could be regulated, which would allow the RRCB to establish.

Sublethal Roundup rates were utilized in an attempt to maintain an acceptable playing surface during the transition. The objective was to determine if the fairway could be renovated in a nondestructive manner where the playing surface would remain acceptable, hence the course remaining open for play during renovation as opposed to the course closing for renovation. Additionally, the scope of this research allows some insight into the success of interseeding bentgrass into established bentgrass stands.

Materials and Methods

The research trial was initiated at the North Carolina State University Turfgrass Field Laboratory on Oct. 10, 2001, on an established Penncross bentgrass area that was maintained as a golf course fairway at 0.4 inch height of cut. The experimental design was a split plot with a factorial arrangement of treatments, including four replications.

The factorial levels included three seedbed preparation variables and six Roundup-application regimes. Evaluated seedbed preparation variables included: vertical mowing in two directions, vertical mowing in two directions plus core aerification with 0.5-inch hollow tines followed by topdressing, and no seedbed preparation (Figure 1).

Figure 1 Turf quality was best in plots that were vertically mowed in two directions. This photo was taken 16 weeks after planting.

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