APPLIED RESEARCH
Reducing the Down-Slope Movement of Transition-Assisting Herbicides By Shawn D. Askew, Ph.D., Assistant Professor of Turfgrass Weed Science; and Dan B. Ricker, John B. Willis and David McCall, Graduate Students and Research Specialist; Virginia Tech
As
the seasons change, so does bermudagrass in the transition zone. Prior to winter, cooler weather forces bermudagrass into dormancy. Common golf-course management practices for dormant bermudagrass is to overseed with perennial ryegrass, providing year-round green color and playability in the transition zone. The next spring, however, the mature perennial ryegrass shades the bermudagrass stolons and competes for nutrients and other resources, limiting bermudagrass growth later in the summer. In areas of the transition zone where temperatures are adequate for the growth of both bermudagrass and perennial ryegrass during the summer, transition herbicides may be used to eliminate unwanted perennial ryegrass, providing desired bermudagrass turf. Depending on location, maintenance budget and personal and clientele expectations, determining the proper transition mechanism is important for an effective transition.
Virginia Tech researchers conducted field trials to evaluate movement of herbicides in surface runoff water. Distance of Observed Perennial Ryegrass Injury due to Down-slope Movement of Four Transition Herbicides 4
Rationale for research
Methods Five transition-assisting herbicides were evaluated for injury to perennial ryegrass: Kerb® (pronamide), Manor™ (metsulfuron), 22
TENNESSEE TURFGRASS FEBRUARY/MARCH 2005
Farmington CC 2004
Distance moved (m)
3.5 3 2.5 2 1.5 1 .5 0
Monument 0.3 oz/A 0.6 oz/A
TranXit 1oz/A
Manor 0.5 oz/A
Kerb 1 lb/A
Figure 1: Monument, TranXit and Manor do not move down slope and injure neighboring perennial ryegrass as much as Kerb. Distance of Observed Perennial Ryegrass Injury due to Down-slope Movement of Three Transition Herbicides – Farmington CC 2004 6 Distance moved (m)
Recent registrations of Monument™ (trifloxysulfuron sodium), Revolver™ (foramsulfuron) and TranXit® (rimsulfuron) for control of cool-season turf in bermudagrass increased the selective weed-control options for transition herbicides. Golf-course superintendents and turfgrass managers can now choose herbicides that can fit their individual situation, offering more control with regards to timing, application rates and sequential applications to provide the fastest, most unnoticeable transition. As a result of previously documented observations and data concerning injury to non-target turf from surface-water runoff, trials were initiated to determine if the newly released herbicides showed similar surface mobility compared to products already on the market. Acquiring data about the potential problems associated with herbicidal runoff provides valuable information to golf course superintendents and turf managers who are selecting chemicals for transitioning their overseeded turf back to bermudagrass. Knowledge about the potential injury involved will also dictate when applications should be made and at which rates are most effective, while reducing potential risks of mobility.
Virginia Tech 2003
5 4 3 2 1 0
Flazasulfuron Monument oz/AKerb 0.5 oz/A 1.5 oz/A 3.0 oz/A 0.3 oz/A 1 lb/A
Figure 2: Flazasulfuron 25DF causes more injury down slope when applied at higher rates.