Effect of Dithiopyr Timing on Establishment of Three Cool-Season Turfgrass Species

Abstract

An experiment was conducted to determine the interval needed between dithiopyr formulation (EC and G) treatments and seeding of tall fescue, perennial ryegrass, and creeping bentgrass. The cover of tall fescue 10 wk after seeding was not reduced when the EC formulation was applied at ≤ 0.84 kg ha−1 ≥ 2 wk before seeding. Dithiopyr G at 0.56 kg ha−1 did not reduce tall fescue cover when applied at ≥ 8 wk before seeding; whereas, 0.84 kg ha−1 required a 12-wk interval between treatment and seeding in one of two years. Perennial ryegrass cover 10 wk after seeding was not reduced with dithiopyr at 0.56 kg ha−1 applied from 2 to 12 wk before seeding. When the dithiopyr G was applied at 0.56 kg ha−1, an 8-wk interval before seeding was needed to prevent a reduction in turf cover. When rates of EC and G dithiopyr were increased to 0.84 kg ha−1 an 8-wk interval was needed for the EC and a 12-wk interval was needed for the G formulation to prevent a reduction in cover in one of two years. Creeping bentgrass cover was not reduced when dithiopyr EC was applied at 0.56 kg ha−1 ≥ 8 wk before seeding. When the EC rate was increased to 0.84 kg ha−1 a 12-wk interval was needed between treatment and seeding in one of two years. When dithiopyr G was applied within 12 wk of seeding creeping bentgrass, the cover was reduced to an unacceptable level regardless of application rate.