Introduction
The first goal of this trial was to evaluate the effects of timing and number of applications on control of anthracnose (Colletotrichum cereale) on an annual bluegrass putting green.
A second goal of this trial was to determine the minimum number of applications necessary to produce acceptable turf quality.
Materials and Methods
The trial was conducted on an annual bluegrass putting green located at Emerald Valley Golf Club in Cresswell, Oregon. Six rotation programs were created and all treatments were sprayed at 3-week intervals. Three ‘early start’ programs were initiated on June 26th (one with 3 applications, one with 4 applications and one with 5 applications). Three ‘late start’ programs were initiated on July 18th (one with 3 applications and two with 4 applications but using different products. Treatment details are presented in table 1.
The site is a sand based chipping green located near the 10th tee. Greens at the course have a history of anthracnose problems and fungal resistance to strobilurin and thiophanate methyl fungicides documented by Dr. Frank Wong at the Turf Pathology Laboratory at University of California at Riverside in 2006.
The individual plots measured 25 square feet (5 X 5). The products were applied with a CO2-powered sprayer using TeeJet 80015 nozzles at 30 psi producing a total spray volume of 2 gallons per 1,000 square feet.
The green was mowed daily at 0.125 inches and occasionally lower using a triplex greens mower. Before the trial started, the green had been fertilized every two weeks at 0.25 lbs nitrogen per 1,000 square feet. As a result, the green was very healthy when the trial began. After the initiation of the trial, fertilizer applications were withheld until the first week of August to encourage disease activity. Fertilizer applications were then resumed on the same schedule as the other golf course putting greens. Irrigation was applied regularly with a RainBird irrigation system with supplemental hand watering as needed. Light sand topdressing was applied every other week during the trial.
Disease activity ratings and plot quality ratings were made on the same dates as the fungicide applications. A final rating was made on October 1st , a couple of days before fall coring. Data from each rating date were subjected to analysis of variance using a randomized complete block design with 3 replications. Differences between means were determined by LSD at the 5% level.
Table 1. Treatment application details for rotation programs
Treatment*26-Jun16-Jul8-Aug29-AugSept. 19Rotation Program 1Lynx (1.5) + Daconil Ultrex (3.2)Medallion (0.5) + Daconil Ultrex (3.2)Banner Max(1.5) + Daconil Ultrex (3.2) Rotation Program 2Lynx (1.5) + Daconil Ultrex (3.2)Medallion (0.5) + Daconil Ultrex (3.2)Banner Max(1.5) + Daconil Ultrex (3.2)Medallion (0.5) + Daconil Ultrex (3.2) Rotation Program 3Lynx (1.5) + Daconil Ultrex (3.2)Medallion (0.5) + Daconil Ultrex (3.2)Medallion (0.5) + Daconil Ultrex (3.2)Banner Max(1.5) + Daconil Ultrex (3.2)Medallion (0.5) + Daconil Ultrex (3.2)Rotation Program 4 Lynx (1.5) + Daconil Ultrex (3.2)Medallion (0.5) + Daconil Ultrex (3.2)Banner Max(1.5) + Daconil Ultrex (3.2) Rotation Program 5 Lynx (1.5) + Daconil Ultrex (3.2)Medallion (0.5) + Daconil Ultrex (3.2)Banner Max(1.5) + Daconil Ultrex (3.2)Medallion (0.5) + Daconil Ultrex (3.2)Rotation Program 6 Lynx (1.5) + Daconil Ultrex (3.2)Signature (4.0) + Daconil Ultrex(3.2)Medallion (0.5) + Daconil Ultrex (3.2)Banner Max(1.5) + Daconil Ultrex (3.2)Untreated checknaNananana
*All rates are in oz product per 1,000 sq ft.
Notes: Lynx is an experimental DMI which is awaiting approval from the EPA. Strobilurin and thiophanate methyl based fungicides were not used in the rotations because of known resistance problems at this site. Results and Discussion
Disease Activity
Disease activity ratings are presented in table 2. Visual differences in disease activity can be seen in figure 1.
Since Emerald Valley Golf Club has an annual problem with Anthracnose, we know that symptoms typically appear around middle to late July. One approach to preventative treatments has been to treat 4 weeks before first symptom appearance. In this trial, our early start date was consistent with this approach. As it turned out, early symptoms were observed by mid July.
The early start programs (Rotations 1, 2, & 3) had less disease than the late start programs (Rotations 4, 5, & 6). Surprisingly, Program 1, with only 3 applications, had the same or less disease than all the other programs including programs 2 & 3 which started early and included 4 and 5 applications, respectively. In this trial, it appears that additional applications made after August 8th for the early start programs were unnecessary.
Programs 1 & 2 had very close to 0 percent disease. Even though Program 3 did not perform as well, the difference in control between Programs 1, 2 & 3 was not statistically different.
Late start rotation programs 4, 5 and 6 had statistically higher disease activity than all early start programs. Rotation program 4 (late start with 3 apps) had the most disease activity of the plots receiving fungicide treatments. All six rotation programs were statistically better than the untreated check plot.
Given the expectations for playing conditions at most golf courses, it is our opinion that only the early start rotations produced acceptable disease control in this trial.
Turf Quality
Turf quality ratings are presented in table 3.
Turf quality was generally statistically higher for the early start rotation programs for the duration of the trial than for the late start rotation programs and the untreated check plot. The difference in turf quality between the early and late start programs may be explained by the location of one replication of the late start programs in the cleanup pass of the mower which lowered turf quality drastically for that replication and resulted in an overall reduction in average turf quality. The higher disease activities in the late start rotations also contributed to the lower quality scores.
All rotation programs produced statistically better turf quality than the untreated check plot.
Of the late start programs, programs 5 & 6 were better than Program 4 but were more than 1 point below the early start programs. The turf quality of Program 4 was fairly similar to programs 5 & 6 through September 18, but then dropped off substantially by October 1.
Conclusions
Early start rotation programs produced the least amount of disease and the highest turf quality ratings in this trial.
The success of rotation program 1 caused us to question the necessity of continuing applications after the middle of August if 3 timely applications are made in June, July, & August.
The results of program 4 (late start with 3 apps) indicate that if you are late with the first application, then additional late season applications are needed to avoid severe disease and poor turf quality.
These results may be explained as follows: If you let the disease develop a critical mass, subsequent applications are only holding it at bay and treatments will be needed clear into September just to avoid severe turf loss. However, if you treat the disease early enough, the disease never gains the critical mass to cause turf damage and late season applications may not be necessary.
Table 2: Average percent area of plots showing Anthracnose symptoms
Percent plot area showing disease symptoms 18-Jul8-Aug29-Aug18-Sep1-OctTrt#TreatmentAvgAvgAvgAvgAvg1Rotation Program 10000.102Rotation Program 20000.10.13Rotation Program 3000.20.10.44Rotation Program 40.40.21.10.32.75Rotation Program 50.50.10.80.61.46Rotation Program 60.101.70.91.27Untreated Check0.51.318.333.338.3 LSD @ .050.30.42.61.92.2
Note: ratings between programs with differences greater than the LSD are statistically different.
Table 3: Average plot turf quality: 1 – 9; 9 = best
Average Plot Quality 18-Jul8-Aug29-Aug18-Sep1-OctTrt#TreatmentAvgAvgAvgAvgAvg1Rotation Program 155.86.86.56.32Rotation Program 2567.26.56.53Rotation Program 35.35.76.56.56.34Rotation Program 45555.54.35Rotation Program 54.75.35.55.25.26Rotation Program 65.35.56.25.35.27Untreated Chck54.72.722 LSD @ .050.60.611.11.1
Note: ratings between programs with differences greater than the LSD are statistically different.
Fig. 1. Relative disease activity on Sept 18, 2007 in rotation program 1 (left) vs. the untreated check plot (right) 