Significant numbers of golf courses in the climatic transition zone attempt to maintain a two-grass fairway system of bermudagrass annually overseeded with perennial ryegrass. Spring transition to bermudagrass is variable and has been linked to overseeding rate, overseeded species and variety, length of dormancy, summer stress, management and herbicide use. No consideration has been given to bermudagrass cultivar influence or interaction regarding fall or spring overseeding transition success. Virginia Tech Researchers with support from golf course superintendents and turfgrass associations are conducting research to investigate the influence of bermudagrass cultivar on fairway fall and spring transition and the impact of transition assisting herbicides on this dynamic system.
Implementation of field trials:
To represent a range of desirable bermudagrass types for the transition zone and south, Midiron, Patriot, Tifsport, Tifway, and Vamont were established at the Turfgrass Research Center in Blacksburg, VA and existing golf fairways of Midiron, Tifway, and Vamont were utilized at Goodyear Golf Club in Danville, VA. Each bermudagrass cultivar was overseeded with perennial ryegrass at 300 and 600 pounds per acre. Treatments included Revolver™ (foramsulfuron) at 9 oz/acre, Kerb™ (pronamide) at 1.5 lb/acre, Manor™ (metsulfuron) at 0.5 oz/acre, TranXit™ (rimsulfuron) 1 oz/acre, Monument™ (trifloxysulfuron) 0.33 oz/acre, aggressive cultural management at 50% bermudagrass green-up (mowing to 0.5 inch, core cultivating, vertical mow in two directions, and 2 lb soluble N/1000 ft2), a nontreated control, and a non-overseeded nontreated control. Note that chosen herbicide rates are based on the lowest company-recommended rate for perennial ryegrass control. Turfgrass cover and chlorophyll content was assessed at various times in the fall and spring, perennial ryegrass control was evaluated at several times after treatment, and bermudagrass injury was evaluated. The objectives of this research were to compare bermudagrass cultivar differences in fall and spring transition under two perennial ryegrass overseeding rates and to evaluate transition-assisting herbicides compared to aggressive cultural treatment for each overseeding rate on each bermudagrass cultivar. This report is not complete as the first year of this two-year study is still underway.
Preliminary data indicate that bermudagrass cultivars impart a strong influence on transition aesthetics, ability to control perennial ryegrass in spring, and ability to achieve perennial ryegrass cover in fall. For example, Midiron was slow to fully recover from the effects of perennial ryegrass competition in the previous year and was characterized by a thin bermudagrass canopy at the golf course location. Fall overseeding was more successful in Midiron compared to other cultivars because the bermudagrass canopy was thinner. Increasing the perennial ryegrass overseeding rate did not improve spring cover but did offer quicker establishment in fall, which could be important for suppressing weedy annual bluegrass. At Blacksburg, low rates of transition herbicides were not enough to completely control perennial ryegrass during a cool spring, however, Patriot bermudagrass seemed to compete with ryegrass more than other cultivars and ryegrass completely died out in all Patriot plots.
Summary and future work:
These are preliminary results and conclusions cannot yet be drawn considering a single year’s data. It seems that bermudagrass cultivar, although previously seldom considered in spring transition discussion, is a major factor that may limit or improve the success of transition programs. Data from this research, upon completion, will be published in leading scientific journals and Golf Course Management magazine.