Fungicide Programming for Dollar Spot Disease Control in Chicago Golf Fairways.

Ten fungicide programs targeting dollar spot (Sclerotinia homoeocarpa) were evaluated in 2008.  Strategies employed were curative, preventive, a curative-preventive hybrid, and two real-time site specific programs.  The study was replicated at two Chicago suburb golf course fairways in play with differences in environment, turfgrass composition, and fungicide resistance.  Plots were 4 ft by 6 ft in size and arranged in a randomized complete block design with four replications.  Fungicides were applied with a CO₂ backpack sprayer and 8004 nozzles at 40 psi in water equivalent to 2 gal/1000 ft².  Percent plot damage and visual quality were estimated.  Area under the curve summarized the entire season, and was analyzed by analysis of variance using Fisher’s Protected LSD.  Fungicide program prices were compared based on a standard using the preventive Daconil Ultrex (chlorothalonil) every 14 days.  Dollar spot was first reported in Chicago on 4 Jun, with peak development of 55% plot damage in Sep (south location) or 45% plot damage in Oct (north location).  All fungicide programs controlled dollar spot compared to untreated.  A hybrid program that timed the first application when symptoms first develop then rotated systemic fungicide families used 5 total applications.  Fungicide programs that reduced the total applications, used low rates, or post-patent materials were found to reduce total cost relative to the chlorothalonil standard.