As seeded bermudagrass (SB) (Cynodon dactylon) varieties continue to perform well in variety trials, more fine turf managers are considering SB for fairways and athletic fields.   Riviera is one seeded variety that has cold-tolerance, color, and quality characteristics equivalent to popular vegetative varieties.   These characteristics make Riviera SB a suitable fairway and athletic field turf in the colder areas of the transition zone, where previously not possible with SB cultivars.   If turfgrass managers adopt this variety, information will be needed to aid weed control efforts during establishment.   The objective of these studies where to determine weed control options for establishing SB and evaluate response of Riviera SB to various herbicides applied pre- and post-seeding.

Two field studies were conducted in Blacksburg, VA to evaluate the following herbicides effects on Riviera SB: foramsulfuron at 0.03 lbs ai/A, trifloxysulfuron 0.42 oz ai/A, metsulfuron 0.60 oz ai/A, rimsulfuron 0.50 oz ai/A, sulfosulfuron 0.48 oz ai/A, and flazasulfuron 0.50 oz ai/A.   These herbicides were applied at timings relative to bermudagrass seeding.   In one field trial Riviera SB was seeded on June 21 treated with the above herbicides one and three weeks preplant, the other field trial was planted June 7 and treated with the above herbicides one and three weeks after seeding.

When applied at any timing, foramsulfuron, sulfosulfuron, and metsulfuron caused little SB injury.   Trifloxysulfuron, rimsulfuron, and flazasulfuron applied 1 week preseeding injured SB 24, 13, and 36 percent, respectively one month after seeding.   This injury resulted in a cover reduction of 15 to 30 percent, 2 months after treatment.  Trifloxysulfuron, rimsulfuron, and flazasulfuron caused slight stunting and chlorosis when applied 3 weeks preseeding, but did not cause significant reduction in SB cover.   When herbicides were applied one week after seeding, SB was most sensitive to injury.   At this timing, many seed are initiating germination and existing seedlings are extremely small.   Herbicides are best applied three weeks before seeding or three weeks after seeding to avoid injury.   In the case of the more injurious products rimsulfuron, trifloxysulfuron, and flazasulfuron, herbicides should be applied 3 weeks after emergence (about 6 weeks after planting).