Abstract/Contents: | "During 1988 and 1989, preemergence herbicide studies were conducted at the Turfgrass Research Center, Stillwater, OK, and Pawhuska Country Club, Pawhuska, OK, to determine their usefulness on bentgrass putting greens under Oklahoma weather conditions in the summer. In 1988, preemergence herbicides evaluated primarily for control of goosegrass on the research bentgrass green included: Rydex 65WDG (0.75, 1.0, and 1.5 lb. prodiamine/A), XL 2G (1.5 lb. benefin + 1.5 lb. oryzalin/A), Betasan 4EC (3.0 lb. bensulide/A), Ronstar (4.0 lb. oxadiazon/A), Scott's Turf Weedgrass Control (3.0 lbs. pendimethalin/A), Gallery 75DG + Surflan 85DG (0, 0.5, 0.75, and 1.0 lb. isoxiben + 1.5 lb. oryzalin/A), Dimension 0.5G (0.25, 0.5, 0.75, and 1.0 lbs. dithiopyr/A), and Dimension 1EC (0.5, 0.75, 1.0, and 1.5 lb. dithiopyr/A). A total plot area of 2.5 ft. by 6 ft. (replicated 3 times) was treated on April 21, using a small CO2 boom delivering 40 gallons of water per acre for soluble products, or a small shaker jar for granular formulations. The experimental area consisted primarily of bentgrass and annual bluegrass which was mowed daily at 5/32 inches. In 1989, preemergence herbicides evaulated primarily for crabgrass and goosegrass control on three greens at Pawhuska Country Club during the summer were: Rydex 65WDG (0.75 lbs. prodiamine/A), Scott's Goose/Crab (3.0 lbs. bensulide/A + 1.5 lbs. oxadiazon/A), Scott's Turf Weedgrass Control (3.0 lbs. pendimethalin/A), Dimension 0.25G (0.25, 0.38, 0.5, and 0.75 lbs. dithiopyr/A), and Dimension 1EC (0.38, 0.5, 0.75, and 1.0 lbs. dithiopyr/A). A total plot area of 5 ft. by 20 ft. (replicated on 3 different greens) was treated on May 4, using a small CO2 boom delivering 40 gallons of water per acre for soluble products, or a small shaker jar for granular formulations. Bentgrass phytotoxicity, postemergence control of annual bluegrass, and preemergence control for annual grassy and broadleaf weeds were evaluated during May through July, 1988. Treatments with Surflan developed noticeable bentgrass discoloration in May only. During June (2 MAT), postemergence control of annual bluegrass was not significantly different. However, evaluations made in late July (3 MAT) started to seperate the treatments for annual grassy and broadleaf weed control. Rydex, Dimension 0.5G, Gallery + Surflan, and Ronstar were the better performers for goosegrass and other grass weeds. Gallery controlled the broadleaf weed spurge the best followed by Rydex, pendimethalin, Ronstar, and Betasan. In 1989, pendimethalin was the only product that caused phytotoxic effects on one of the three greens tested. Acceptable crabgrass control resulted for all treatments except Scott's Goose/Crab at 2 MAT, and at 2 MAT Scott's Goose/Crab, Dimension 0.25G at 0.25 lbs./A, and Rydex 65WDG at 0.75 lbs./A were starting to let crabgrass break through. At 2 MAT, goosegrass was acceptable for all eleven herbicide treatments; however, several products were no longer controlling goosegrass at 3 MAT. Rydex, Scott's Goose/Crab, and Dimension at 0.5 lbs. to 1.00 lbs. dithiopyr/A were providing acceptable control at 3 MAT." |