The purpose of this trial was to evaluate the effectiveness of various fungicides and kelp in controlling anthracnose (Colletotrichum cereale) on annual bluegrass putting greens.
Materials and Methods
The trial was initiated on June 23rd on an 80 percent annual bluegrass/20 percent creeping bentgrass nursery green located at Eugene Country Club in Eugene, Oregon, which is approximately 90 miles south of Portland. The course has a history of moderate anthracnose problems. Subsequent fungicide and kelp applications were applied every 2 weeks on July 7th, July 21st, August 4th, and August 18th and September 1st.
Anthracnose is thought to be a disease of weak and senescing turf. Cytokinins have been known to reduce leaf senescence in some cases and kelp is known to be high in cytokinins. Kelpgrow was chosen as the cytokinin product to apply for no particular reason other than we had some on our shelves. It was later discovered that Kelpgrow also includes abscisic acid which tends to inhibit the cytokinin response. This inhibition may explain why Kelpgrow did not improve turf quality over the untreated check.
Daily high temperatures and relative humidity at the time of high temperature for the dates of applications are listed in the table below:
|Date of application||Daily High Temperature (F)||Relative Humidity|
The trial site was a nursery green that was initiated from aerification plugs taken from the golf course during the fall of 2007 and placed on a six inch sand base. The green was located at the end of the driving range and some golfers were able to fly their golf balls onto the green resulting in numerous ball marks. Since the nursery green was not in play, the ball marks were not repaired. The green was initially fertilized with 1 pound of nitrogen per 1,000 sq. ft. using Anderson’s 18-9-08 Contec DG in the fall with establishment and another 1 pound of nitrogen (same fertilizer) per 1,000 sq. ft. in the spring. This green was the site of a fungicide screening trial for anthracnose in 2008. In order to encourage anthracnose during the 2008 trial, only one application of soluble fertilizer was made on July 14th, 2008 applying 0.20 pounds of nitrogen per 1,000 sq. ft. Normal fertilizer applications were resumed in the fall and carried out through spring.
In 2009, two soluble fertilizer applications were made. The first was made in the first week of July applying 0.25 lbs of N per 1,000 sq. ft. The second application was made the first week of August applying 0.30 lbs of N per 1,000 sq. ft. In early July, a lightning strike knocked out an irrigation control unit causing moderate drought stress. Irrigation was applied with a RainBird irrigation system. The green was walked mowed at 0.105 inches throughout the trial.
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 two gallons per 1,000 sq. ft.
Visual disease severity and plot quality ratings were taken on July 21st, August 4th, August 11th, August 18th and August 25th. Disease severity ratings were based on percent plot cover from 0 – 100 percent. Turf Texture ratings (1 – 9 scale; 9 = finest leaf texture) were made on July 21st, August 4th, August 18th, and September 1st. Turf color ratings were based on digital photographs taken on the same dates and analyzed using Sigma Scan Pro software from SPSS, Inc (See Karcher, D.E. and Richardson, M.D. 2003. Quantifying Turfgrass Color Using Digital Image Analysis. Crop Sci. 43:943-951). 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 Fisher’s LSD at the 5% level.
The treatments applied are listed below:
|Trt #||Treatment||Rate (oz./1000 ft^2)|
|6||Reserve + Signature||3.2 + 4.0|
|Trt #||Treatment||Rate(oz./1000 ft^2)|
|10||Triton FLO rotated with Signature + Daconil Ultrex||0.75/4.0 + 3.2|
|11||Rotation Program (See below)||See below|
Treatment 11 Rotation Program:
|Treatment||Rate (oz./1000 ft2)||Date of Application|
|Triton FLO||0.75||June 23rd|
|Triton FLO||0.75||July 7th|
|Signature + Daconil Ultrex||4.0 + 3.2||July 21st|
|Signature + Daconil Ultrex||4.0 + 3.2||August 18th|
|Triton FLO||0.75||September 1st|
Disease symptoms began showing up in the middle of July. Foliar anthracnose was confirmed by the OSU Disease Lab. The untreated check plots averaged 6.7 percent disease by July 21st. By August 4th, the disease severity on the untreated plots increased to 23 percent. The disease severity peaked in the untreated check plots on August 25th averaging 25 percent. A big rain storm combined with decreasing temperatures in early September brought stress relief and a marked decrease in disease severity. By September 8th, the untreated check had 10 percent disease.
All products, with the exception of Kelpgrow, provided excellent disease control. At the peak of disease pressure (August 25th), plots treated with Triton FLO at 0.75 oz. per 1,000 ft2 and Banner Maxx at 1.0 and 2.0 oz. per 1,000 ft2 had 1.0, 0.2, and 1.2 percent disease, respectively. With the exception of Kelpgrow and the untreated check, all other plots averaged 0.3 percent disease or less on August 25th.
Interestingly, the 0.75 oz. rate of Triton FLO had more disease and lower turf quality on August 18th and August 25th than the 0.5 oz. rate of Triton FLO. The difference in disease was minor and not statistically different. The lower turf quality was likely caused by repeated applications of a higher rate of a DMI fungicide. See note on Banner Maxx, below.
Generally, most of the treatments provided good to excellent turf quality. The rotation program (Trt 11), Triton FLO rotated with Signature + Daconil Ultrex (Trt 10), and Reserve + Signature (Trt 6) provided slightly better turf quality than the other treatments. Plots treated with Banner Maxx (propiconazole) at 2.0 oz. per 1,000 ft2 had turf quality which got worse over time related to an excessive plant growth regulator (PGR) effect (leaf yellowing and thickening) known to occur when DMI fungicides are applied too often or at too high a rate. The plots treated with Banner Maxx at 1.0 oz per 1,000 ft2 or Concert (propiconazole + chlorothalanil) at 5.0 oz. per 1,000 ft2 did not have the excessive PGR effect. The 5.0 oz per 1,000 ft2 rate of Concert is equivalent to a 1.2 oz. per 1,000 ft2 rate of propiconazole if applied as Banner Maxx.
Since most of the products applied in this trial were DMI fungicides, turf texture ratings were taken as a gauge of the PGR effect. Generally, as the rates of these products increased, leaf thickening (or leaf coarseness) also increased.
There were some lines of demarcation where the PGR effect appeared to get much worse. For Triton FLO, there was a noticeable growth regulator effect at 0.75 oz. per 1,000 ft2. However, when the rate went from 0.75 to 1.0 oz., the growth regulator effect spiked and became borderline acceptable. The 1.0 oz. rate of Triton Flo produced a similar leaf thickening (without yellowing) as was seen in the 2.0 oz. rate of Banner Maxx.
Reserve (triticonazole + chlorothalanil) applied at 3.2 oz. per 1,000 ft2 has an equivalent rate of triticonazole applied in Triton FLO at 0.56 ounces. Plots treated with Reserve at the 3.2 ounce rate only had a minor PGR effect. As the Reserve rate increased to 3.6 oz. per 1,000 ft2 (equivalent to a 0.63 oz. per 1,000 ft2 rate of triticonazole applied as Triton FLO), the PGR effect increased. However, there was a bigger jump in PGR effect when the Reserve rate went to 4.5 oz. per 1,000 ft2.
Turf color was rated by taking digital photos inside a light box and evaluating the photos using Sigma Scan Pro software from SPSS, Inc. Treatments that included Triton FLO, Reserve, or Signature were generally slightly darker than Concert, Banner Maxx, or the Kelpgrow. The difference was likely caused by the pigment that is included in the Triton FLO, Reserve, and Signature fungicides. On some dates, the differences were not statistically significant. Reserve + Signature (Trt 6) had the darkest color of all the treatments because both the Reserve and the Signature fungicides have the pigment in them, thus doubling the amount of pigment and further darkening the turf.
Table 1: Percent Disease Ratings (0 – 100%)
|Trt #||Treatments||Rate oz./1,000 ft^2||Percent Disease 21-Jul||Percent Disease 4-Aug||Percent Disease 11-Aug||Percent Disease 18-Aug||Percent Disease 25-Aug|
|6||Reserve + Signature||3.2 + 4.0||0||0||0||0||0|
|10||Triton FLO rotated with Signature + Daconil Ultrex||0.75/4.0 + 3.2||0||0||0||0||0|
|11||Rotation Program||See above||0||0||0||0.2||0.2|
|LSD @ .05||0.9||3.4||3.5||3.4||4|
Table 2: Turf Quality Ratings (1 – 9; 9 = best)
|Trt #||Treatments||Rate oz./1,000 ft^2||Turf Quality 21-Jul||Turf Quality 4-Aug||Turf Quality 11-Aug||Turf Quality 18-Aug||Turf Quality 25-Aug|
|6||Reserve + Signature||3.2 + 4.0||7||8||8.3||8.2||7.8|
|10||Triton FLO rotated with Signature + Daconil Ultrex||0.75/4.0 + 3.2||7||7.5||8||8||7.5|
|11||Rotation Program||See above||6.3||7.7||7.8||7.8||8|
|LSD @ .05||ns||0.7||0.9||0.9||0.9|
Table 3: Turf Texture Ratings (1 – 9; 9 = finest texture)
|Trt #||Treatment||Rate oz./1,000 ft2||21-Jul Avg||4-Aug Avg||18-Aug Avg||1-Sep Avg||Cumm Avg|
|6||Reserve + Signature||3.2 + 4.0||7||7||7||7||7|
|10||Triton FLO rotated with Signature + Dac Ultrex||0.75/4.0 + 3.2||6.8||7||7.2||7||7|
|11||Rotation Program||See above||7.2||7.2||6.5||7||7|
|LSD @ 5%||0.5||0.5||0.5||0.6||na|
Table 4: Turf Color Ratings (1 – 9; 9 = darkest green)
|Trt #||Treatment||Rate oz./1,000 ft2||7-Jul Avg||21-Jul Avg||4-Aug Avg||18-Aug Avg||1-Sep Avg||Cumm Avg|
|6||Reserve + Signature||3.2 + 4.0||6.8||7.8||8.2||8||7.8||7.7|
|10||Triton FLO rotated with Signature + Dac Ultrex||0.75/4.0 + 3.2||6.7||7.7||7.7||7.7||6.8||7.3|
|11||Rotation Program||See above||6.5||7.5||7.8||7.8||7.5||7.4|
|LSD @ 5%||0.8||0.8||0.7||0.8||1.2||Na|