Chemical Control of Spring Dead Spot in Bermudagrass Fairways.

Field experiments were conducted at Hillcrest Country Club in Lubbock, TX during the fall of 2009 to evaluate the chemical control of spring dead spot (SDS) in a bermudagrass fairway. Plots measuring 1.5 m² were arranged in a randomized complete block design with four treatment replications. Treatments were applied using a CO₂ backpack sprayer equipped with XR8008VS nozzles calibrated to deliver 757 L/ha at 220 kPa. Initial applications were made on 9/25/2009 and consisted of single or sequential applications of fenarimol (1.52 or 2.29 kg ai/ha) + thiophanate-methyl (7.62 or 9.16 kg ai/ha) or fenarimol (1.52 or 2.29 kg ai/ha) followed by (fb) thiophanate-methyl (7.62 or 9.16 kg ai/ha). Sequential applications were made 30 days after initial treatment (DAIT). All applications included Grounded (surfactant + aliphatic hydrocarbons) at 2.34 L/ha. Control ratings were conducted the following spring (2010) when symptoms appeared following bermudagrass green-up. Visual ratings of % disease cover were conducted every two weeks until bermudagrass recovered in the summer. Data were subjected to analysis of variance (ANOVA) and means were separated using Fisher’s Protected LSD (α=0.05). Fenarimol (2.29 kg ai/ha) fb thiophanate-methyl (7.62 kg ai/ha) and sequential applications of fenarimol (2.29 kg ai/ha) + thiophanate-methyl (7.62 kg ai/ha) and fenarimol (2.29 kg ai/ha) + thiophanate-methyl (9.16 kg ai/ha) exhibited 9, 6, and 2% disease cover, respectively, on 4/23/2010. All other treatments exhibited 18 to 25% disease cover, while untreated check plots exhibited 26% disease cover on 4/23/2010. Significant disease pressure (>11%) remained in plots receiving single treatment applications or the lowest fenarimol rate (1.52 kg ai/ha) on 6/29/2010, while fenarimol (2.29 kg ai/ha) fb thiophanate-methyl (7.62 kg ai/ha) and sequential applications of fenarimol (2.29 kg ai/ha) + thiophanate-methyl (7.62 kg ai/ha) and fenarimol (2.29 kg ai/ha) + thiophanate-methyl (9.16 kg ai/ha) were reduced to ≤ 5% disease cover.