Evaluation of Start Date and Number of Applications for Control of Anthracnose On An Annual Bluegrass Putting Green.

This trial investigated the effectiveness of fungicide rotations applied every 3 weeks using two start dates (early start - June 26,  late start - July 18) combined with 3, 4, & 5 applications to control anthracnose (Colletotrichum cereale ).  The fungicides used in the rotations were Lynx (tebuconazole + StressGard™), Medallion, Banner Maxx, and Signature all mixed with Daconil Ultrex.    The trial site was  a sand-based practice green located at Emerald Valley G.C.  in Cresswell, Oregon, which had a history of anthracnose and confirmed resistance to strobilurin and thiophanate methyl fungicides with first disease symptoms normally appearing in mid July.   Nitrogen was limited early in the trial to encourage disease and the green was maintained in accordance with current putting green standards.  Plots were rated visually every 3 weeks for percent disease cover and turf quality.  Data were subjected to analysis of variance and means separated using Fisher’s protected LSD (α=0.05). There was no difference in percent disease cover or turf quality between the early start fungicide programs even though Program 1 had only three fungicide applications and Programs 2 and 3 had four and five fungicide applications, respectively.   All three early start programs had less than 0.5 percent disease cover at the conclusion of the trial, whereas the untreated plots averaged 38 percent disease cover.  The three late start rotation programs had significantly worse turf quality than the early start programs but only slightly more disease.  The worst disease and turf quality resulted from Program 4 – late start with only three fungicide applications.  The results of this trial suggest that it may be possible to reduce fungicide applications later in the summer if the initial application is timed correctly.