Fungicide Alternatives for the Management of Microdochium Patch Clint Mattox, Alec Kowalewski, and Brian McDonald Oregon State University May 2017 Introduction: Previous trials indicated promising results for the control of Microdochium patch on Poa annua putting greens using the combination of the mineral oil Civitas One with sulfur and/or phosphorous acid, as well as a sulfur and phosphorous acid combination. Other previous trial results have indicated that iron sulfate heptahydrate has shown the potential for control of Microdochium patch on Poa annua putting greens. However, some questions remain, namely concerning abiotic damage that was observed when rolling was used in combination with Civitas One. This is a major concern for turfgrass managers as rolling and other forms of mechanical stress are typical cultural practices used to maintain high quality putting surfaces. Another concern is turfgrass thinning associated with frequent high rates of iron sulfate heptahydrate. Regarding these concerns, in the fall of 2015 a series of new trials were initiated to explore methods for alleviating abiotic damage caused by these fungicide alternative methods for Microdochium patch management. The first goal of these trials was to identify minimum effective rates using alternative product combinations and rotations of Civitas One, phosphorous acid and sulfur (Experiments 1 and 2). The second goal was to determine if increased water carrier volumes or application timing intervals of iron sulfate heptahydrate would continue to suppress Microdochium patch while alleviating turfgrass thinning compared to the original twoweek interval or 2 gal/m carrier volume (Experiments 3 and 4). Other new trials include exploring alternative crop oils; Civitas One, Superior Oil and TriTek Oil (Experiment 5), and phosphorous acid products; PK Plus or Duraphite 12 used in combination with sulfur (Experiment 6). Experiments 1, 2, 4, and 5 received replicated golfer traffic (73 rounds of golf a day) in order to mimic real-world conditions and to assess any abiotic damage that may result. Research on all 6 experiments was conducted on Poa annua putting greens at the Lewis- Brown Turf Farm, Corvallis, OR. These putting greens were vegetatively established using aerification cores spread over a layer of USGA sand in 2009 (1, 2, 4, and 5) or 2013 (3 and 6). Page 1 of 10
Experiment 1: Objective: Determine the most reliable and cost effective rate of the combination of the mineral oil Civitas One, Sulfur DF and the phosphorous acid product PK Plus to control Microdochium patch on Poa annua putting greens, while assessing abiotic damage under replicated golfer traffic. Treatments were applied every two weeks from Sept. 2015 to April 2016 and again from Sept. 2016 to April 2017. Experiment 1 Results: This trial reproduced the abiotic damage under replicated traffic that was observed in previous trials. The most striking damage was observed whenever Civitas One was applied with sulfur regardless of rates. In addition to the Civitas One & sulfur combinations, Civitas One applied at 8.5 oz. / M every two weeks in combination with PK Plus had at least one replicate with unacceptable turf quality when the abiotic damage was at its peak in both years (01-25-16 & 01-29-17 respectively). All treatment combinations reduced the incidence of Microdochium patch compared to the control (Image 1 and Table 1). Image 1: Effects of high rates of Civitas One + Sulfur (left), and Civitas One + PK Plus (middle) compared to the control plot in January 2016. Page 2 of 10
Table 1: Mineral Oil, Phosphorous Acid, & Sulfur Rate Trial Year One: 2015-2016 AUDPC v Turf Quality x Turf Quality Treatments z 1/25/16 3/18/16 4.25 oz. Civ + 0.125 # S 4 ab v 5.9 ab 7.8 a 4.25 oz. Civ + 0.25 # S 0 a 5.5 ab 6.0 ab 4.25 oz. Civ + 3.0 oz. PK Plus 85 ab 6.5 a 7.0 ab 4.25 oz. Civ + 6.0 oz. PK Plus 53 ab 6.1 ab 6.3 ab 8.5 oz. Civ + 0.125 # S 0 a 4.5 ab 8.0 a 8.5 oz. Civ + 0.25 # S 0 a 3.3 b 5.1 ab 8.5 oz. Civ + 3.0 oz. PK Plus 8 ab 5.8 ab 7.8 a 8.5 oz. Civ + 6.0 oz. PK Plus 0 a 6.3 a 8.0 a Not treated 2292 b 5.0 ab 3.0 b Year Two: 2016-2017 Turf Quality Turf Quality AUDPC Treatments 1/29/17 2/25/17 4.25 oz. Civ + 0.125 # S 83 ab 5.3 ab 5.6 ab 4.25 oz. Civ + 0.25 # S 33 ab 6.1 a 6.5 a 4.25 oz. Civ + 3.0 oz. PK Plus 152 ab 5.1 ab 5.4 ab 4.25 oz. Civ + 6.0 oz. PK Plus 15 ab 6.3 a 6.8 a 8.5 oz. Civ + 0.125 # S 30 ab 4.3 ab 5.0 ab 8.5 oz. Civ + 0.25 # S 44 ab 3.0 ab 4.0 ab 8.5 oz. Civ + 3.0 oz. PK Plus 4 a 6.1 a 6.8 a 8.5 oz. Civ + 6.0 oz. PK Plus 7 a 6.0 ab 6.8 a Not treated 5151 b 1.8 b 2.8 B z Treatments = applied per 1000ft 2 every two weeks, Civ = Civitas One, S = Sulfur DF y AUDPC = Area under disease progress curve calculated from onset of disease to peak of disease (11/04/15 to 03/18/16 for year one and from 10/07/16 to 02/25/17 for year two) x Turf quality = ratings assigned according to the NTEP rating system v Means sharing a letter in common in the same column are not significantly different according to the Dunn s all pair-wise comparison test (alpha 0.05) Page 3 of 10
Experiment 2: Objective: Determine if applications of the combinations of Civitas One and Sulfur DF or Civitas One and PK Plus in rotation with Sulfur DF and PK Plus would lead to acceptable control of Microdochium patch on Poa annua putting greens while lessening any effects of abiotic damage previously observed in bi-weekly combinations of the mineral oil Civitas One. The following treatments were applied from Sept. 2015 to Apr. 2016 and again from Sept. 2016 to Apr. 2017. 1a. 8.50 oz/m Civitas One + 0.25 lbs. S/M every four weeks (M = 1 000ft2) 1b. 0.25 lbs. S/M + 6.0 oz/m PK Plus every four weeks (alternate with 1a.) 2a. 8.50 oz/m Civitas One + 6.0 oz/m PK Plus every four weeks 2b. 0.25 lbs. S/M + 6.0 oz/m PK Plus every four weeks (alternate with 2a.) 3. 0.25 lbs. S/M + 6.0 oz/m PK Plus every two weeks 4. Control (Not treated) Experiment 2 Results: Similar to experiment 1, whenever Civitas One was applied in combination with sulfur, abiotic damage occurred under replicated traffic in the winter months (Image 2 and Table 2). The treatment 2 rotation (2a & 2b) showed promising results with no winter damage and good Microdochium patch suppression in the both years of this experiment in Corvallis, OR. Image 2: Effects of Civitas One and sulfur (Sulfur DF) or Civitas One and PK Plus in rotation with sulfur and PK Plus in January 2016. Page 4 of 10
Table 2: Effects of Civitas One and Sulfur DF or Civitas One and PK Plus in rotation with Sulfur DF and PK Plus Year One: 2015-2016 Treatments x AUDPC z Turf Quality y Turf Quality 1/25/16 2/16/16 Civ + S rotation w/ S + PK Plus 27 ab v 5.1 ab 6.0 ab Civ + PK Plus rotation w/ S + PK Plus 0 a 6.9 a 7.0 a S + PK Plus / 2wks 0 a 6.3 ab 6.0 ab Not treated 1130 b 4.8 b 4.0 b Year Two: 2016-2017 Treatments AUDPC Turf Quality Turf Quality 1/29/17 2/25/17 Civ + S rotation w/ S + PK Plus 10 a 5.0 ab 7.0 a Civ + PK Plus rotation w/ S + PK Plus 0 a 6.0 a 7.0 a S + PK Plus / 2wks 47 ab 5.6 ab 5.6 ab Not treated 3187 b 2.8 b 3.0 b z Treatments = applied per 1000ft 2 every two weeks, Civ = Civitas One, S = Sulfur DF y AUDPC = Area under disease progress curve calculated from onset of disease to peak of disease (10/14/15 to 02/16/16 for year one and from 10/07/16 to 02/25/17 for year two) x Turf quality = ratings assigned according to the NTEP rating system v Means sharing a letter in common in the same column are not significantly different according to the Dunn s all pair-wise comparison test (alpha 0.05) Page 5 of 10
Experiment 3 Objective: Compare different water carrier volumes for iron sulfate heptahydrate applications in order to assess if a higher dilution will lead to less turfgrass thinning while at the same time continue to manage Microdochium patch on Poa annua putting greens. The following treatments were applied every other week from September 2015 to April 2016 and again from September 2016 to April 2017. 1. 2.0 #/M FeSO 4 Heptahydrate applied using a 2.5 gal/m spray volume every two weeks (M = 1 000ft 2 ) 2. 2.0 #/M FeSO 4 Heptahydrate applied using a 5.0 gal/m spray volume every two weeks 3. 2.0 #/M FeSO 4 Heptahydrate applied using a 7.5 gal/m spray volume every two weeks 4. 2.0 #/M FeSO 4 Heptahydrate applied using a 10.0 gal/m spray volume every two weeks 5. Control (Not treated) Experiment 3 Results: There is suggestion that the water carrier volume does not play a large role in the ability of the application of 2 # FeSO 4 / M every two weeks to suppress Microdochium patch. Under replicated golfer traffic, there is suggestion that there is a minor advantage of using a larger water carrier to decrease the blackening of the turfgrass leaves and to have a slight reduction in turfgrass thinning due to the frequent applications of iron sulfate (Image 3). Image 3: Effects of 2.5 (left) and 10.0 gallon/m carrier volume (middle) when applying iron sulfate heptahydrate compared to the control (right) in March 2016. Page 6 of 10
Experiment 4 Objective: Compare application timings of iron sulfate heptahydrate to quantify the minimum application intervals necessary to suppress Microdochium patch on Poa annua putting greens. The following treatments were applied according to the schedule below from October 2015 to April 2016 and again from October 2016 to April 2017 1. 2.0 #/M FeSO4 Heptahydrate applied using a 5.0 gal/m spray volume every 2 weeks (M = 1 000ft2) 2. 2.0 #/M FeSO4 Heptahydrate applied using a 5.0 gal/m spray volume every 4 weeks 3. 2.0 #/M FeSO4 Heptahydrate applied using a 5.0 gal/m spray volume every 6 weeks 4. 2.0 #/M FeSO4 Heptahydrate applied using a 5.0 gal/m spray volume every 8 weeks 5. Control (Not treated) Experiment 4 Results: There is suggestion that the application frequency of every two weeks (treatment 1) is the only treatment that provided acceptable disease suppression, although turfgrass thinning was also observed leading to unacceptable turfgrass quality (Image 4). Image 4: Effects of iron sulfate heptahydrate applied every two (left), four (middle) and eight weeks (right) in March 2016. Page 7 of 10
Experiment 5 Objective: Compare three different mineral oils in combination with phosphorous acid in their ability to control Microdochium patch on Poa annua putting greens under replicated golfer traffic in order to determine if there are differences in abiotic damage observed and to perhaps find more cost-effective product choices. The following treatments were applied every other week from September 2015 to April 2016 and again from Sept. 2016 to April 2017. 1. 8.50 oz/m Civitas One + 6.0 oz/m PK Plus every two wks (M = 1 000ft 2 ) 2. 7.92 oz/m Superior Oil + 6.0 oz/m PK Plus + 0.37 oz/m of the pigment PAR every two wks 3. 7.92 oz/m Superior Oil + 6.0 oz/m PK Plus every two wks 4. 9.80 oz/m TriTek Oil + 6.0 oz/m PK Plus + 0.37 oz/m of the pigment PAR every two wks 5. Control (Not treated) Experiment 5 Results: There is suggestion that all mineral oils tested have the potential to suppress Microdochium patch when used in combination with PK Plus. Abiotic damage due to repeated applications every two weeks under replicated traffic throughout the winter is still a concern with all products tested. Page 8 of 10
Experiment 6 Objective: Compare two phosphorous acid products alone and in combination with Sulfur DF in order to quantify their ability to control Microdochium patch on Poa annua putting greens. The following treatments were applied every other week from October 2015 to April 2016 and again from October 2016 to April 2017. 1. 6.0 oz/m PK Plus every two weeks (M = 1 000ft 2 ) 2. 3.14 oz/m Duraphite 12 every two weeks 3. 6.0 oz/m PK Plus + 0.25 lbs. S/M every two weeks 4. 3.14 oz/m Duraphite 12 + 0.25 lbs. S/M every two weeks 5. 0.25 lbs. S/M every two weeks 6. Control (Not treated) Experiment 6 Results: There is suggestion that all treatments suppress Microdochium patch compared to the control with better disease control observed when either phosphorous acid product is used in combination with sulfur (Table 3). The combinations of either phosphorous acid product with sulfur were in the group with the highest turf quality in both years. Page 9 of 10
Table 3: Effects of Sulfur DF and phosphorous acid, either alone or in combination to mitigate Microdochium patch on an annual bluegrass putting green in Western Oregon over two years. H3PO3 u AUDPC z 2015-2016 Turf Quality y 2-16-16 Sulfur x No Sulfur Sulfur No Sulfur Dur 12 w 54 a v 47 a H3PO3 Dur 12 5.875 a 5.5 ab PK Plus t 124 ab 338 ab PK Plus 5.75 a 4.75 ab None 347 ab 976 b None 5 ab 4 b H3PO3 AUDPC 2016-2017 Turf Quality 3-18-17 Sulfur No Sulfur Sulfur No Sulfur Dur 12 0 a 29 ab H3PO3 Dur 12 7 a 5 ab PK Plus 0 a 107 ab PK Plus 6.5 a 5 ab None 6 ab 1032 b None 5.875 ab 3 b z AUDPC = Area under disease progress curve calculated from onset of disease to peak of disease (10/14/15 to 02/16/16 for year one and from 11/04/16 to 03/18/17 for year two) y Turf quality = ratings assigned according to the NTEP rating system x Sulfur = Sulfur DF applied at 0.25#/1000ft 2 every two weeks w Dur 12 = Duraphite 12 applied at 3.14 oz./1000ft 2 every two weeks v Means sharing a letter in common in the same column are not significantly different according to the Dunn s all pair-wise comparison test (alpha 0.05) u H 3 PO 3 = Phosphorous acid t PK Plus applied at 6.0oz./1000ft 2 every two weeks Page 10 of 10