Research Update: Effects of Alternatives to Traditional Fungicides and Winter Fertilization Practices on Microdochium Patch
Clint Mattox, Alec Kowalewski, and Brian McDonald Department of Horticulture, Oregon State University
Introduction: Microdochium patch can be observed year-around in some cool, humid regions, and damages nearly all grass species in Western Canada and the Pacific Northwest. Microdochium patch is a major disease on golf course putting greens from September through May, and under favorable conditions, can injure or kill significant amounts of turf which greatly disrupts the aesthetics and playability of the putting green surface. Historically, more money has been spent on fungicides to combat this disease in Western Canada and the Pacific Northwest than any other turfgrass disease. Currently, fungicides applied every 3 to 4 weeks to putting greens throughout the 9 month period of disease activity are the primary means for providing control of this pathogen, which equates to roughly $20,000 annually per golf course.
In recent years, increasing pesticide bans and restrictions have limited the options for managing pest problems including diseases like Microdochium Patch. Considering this, little information exists regarding alternative integrated management strategies that might significantly reduce or eliminate the need for fungicide applications. The overall objective of this research theme is the exploration of fungicide alternative management of Microdochium patch on annual bluegrass putting greens.
Research Update (September 26, 2013 to March 01, 2014):
In continued exploration of fungicide alternative products and practices for management of Microdochium patch a series of experiments were initiated at the Oregon State University Lewis Brown Horticulture Farm and at the Washington State University Goss Research Farm, Puyallup, WA on September 26, 2013 (Image 1).
Image 1: Graduate Assistant, Clint Mattox, applies a series of fungicide alternative products exploring pesticide free control of Microdochium patch at the OSU Lewis Brown Farm in Corvallis, OR, September 26, 2013.
Alternatives to Traditional Fungicides (Table 1 and Image 2):
The objective of this study was to evaluate the efficacy of alternatives to traditional fungicides for the control of Microdochium patch on an annual bluegrass putting green. Fungicide alternative treatments applied every other week since September 26, 2014 included Sulfur DF (0.25 lbs/1,000 ft2; 12.21 kg/ha), Civitas One (8.5 oz/1,000 ft2; 27.06 L/ha), PK plus L (6.0 oz/1,000 ft2; 19.10 L/ha), as well as all possible combinations of these products, in comparison to an untreated check plot (Table 1). Rolling was also investigated as a cultural practice to reduce disease in combination with the fungicide alternative treatments.
Image 2: Effects of Sulfur DF (0.25 lbs/1,000 ft2; 12.21 kg/ha) and Civitas One (8.5 oz/1,000 ft2; 27.06 L/ha), applied every 2 weeks (left) in comparison to the control (right) observed November 20, 2013 (applications initiated September 26, 2013).
The untreated check plots averaged 45.0 percent disease cover on rating date, Mar 1, 2014 (Table 1). When Civitas One was mixed with any of the fertilizer combinations (Sulfur, PK plus, or Sulfur and PK plus) 0.5 percent disease or less was observed (Image 2). Civitas One, Sulfur and PK plus alone were able to provide some disease control, but none were able to provide acceptable control for putting green quality. In March, rolling reduced disease severity only when the products discussed above where not applied. When these products were applied, rolling had little effect on disease severity, or turf color and quality. Rolling in combination with all plots where Civitas One was applied began to show signs of abiotic damage on 09 Jan 2014. The manufacturers of Civitas One recommend only applying it when the turf is actively growing. This suggests that the decreasing temperatures in combination with rolling led to a decline in turf quality.
Winter Fertilization Practices (Table 2 and Image 3):
The objective of this study was to evaluate the efficacy of winter fertility practices in combination with simulated traffic in order to determine their effects on the suppression of Microdochium patch and turfgrass recovery on annual bluegrass in western Oregon, 2013-2014. Treatments applied in this study every other week beginning September 26, 2014 included iron sulfate applied at 0.0, 0.25, 0.5, 1.0 and 2.0 lbs/1,000 ft2 (0.0, 12.21, 24.41, 48.82 and 97.65 kg/ha) and nitrogen (46-0-0) applied at 0.0, 0.1 and 0.2 lbs N/1,000 ft2 (0.0, 4.88 and 9.76 kg/ha) as well as all possible combinations of these iron sulfate and nitrogen rates (Table 2). All treatments then received weekly foot traffic at a rate equivalent to Trysting Tree Golf Course in Corvallis, OR.
Image 3: Effects of iron sulfate, applied at 2.0 lbs FeSO4/1,000 ft2 (97.65 kg FeSO4/ha) every 2 weeks (left), and nitrogen (46-0-0), applied at 0.1 lbs N/1,000 ft2 (4.88 kg N/ha), plus iron sulfate, at 2.0 lbs FeSO4 per 1,000 ft2 (97.65 kg FeSO4/ha) every 2 weeks (right) on Microdochium patch incidence and annual bluegrass putting green health, picture collected Jan 10, 2014 (4 months after the fall 2013 initiation date). Note: the poor quality associated with the plot on the left is the result of foot traffic, which is applied to all treatments in the study.
As of March 1, 2014, the untreated control plots averaged the highest disease severity, 55%. Plots that received iron sulfate at 2.0 lbs/1,000 ft2 (97.65 hg/ha) with nitrogen applied at the 0.1 lbs N/1,000 ft2 (4.88 kg/ha) rate and without nitrogen had the lowest percent of disease (Table 2 and Image 3). When iron sulfate was applied at 2.0 lbs/1,000 ft2 (97.65 kg/ha) in combination with nitrogen at the 0.2 lbs N/1,000 ft2 (9.76 kg/ha) rate disease pressure increased. While iron sulfate applied at 2.0 lbs/1,000 ft2 (97.65 kg/ha) without nitrogen provided some of the lowest disease percentage it also produced some of the lowest turf quality and color ratings due the foot traffic applied throughout the winter. Plots that received iron sulfate at 2.0 lbs/1,000 ft2 (97.65 kg/ha) in combination with nitrogen applied at the 0.1 lbs N/1,000 ft2 (4.88 kg/ha) rate were able to maintain acceptable turf quality and color throughout the winter traffic period.
Reduced Cost:
Initial calculations derived using promising preliminary findings (effects of Civitas One applied with Sulfur DF) translates to substantial financial savings. For instance, it would cost $5,470 to treat 2 acres of putting greens over 9 months at the rates utilized in this research. This represents a $14,500 savings for the typically golf course, and $4,500,000 saving for the Pacific Northwestern United States [1,653 acres (669 hectares)]. Applications of Civitas One plus potassium phosphite (PK plus), and iron sulfate plus light rates of nitrogen would translate to similar savings and provide a fungicide alternative rotation for elemental sulfur (Sulfur DF) applications. Preliminary additional studies this spring are showing that it may not be necessary to apply these products every two weeks. Obviously, reducing the number of applications would further increase savings over traditional fungicide programs.
Fewer Fungicides:
While these projected financial savings are significant, it is important to point out that this control is being provided without the use of traditional fungicides, which are continually facing increasing bans and restrictions across the United States, Canada and the world. Projected fungicide applications on a typical golf course for control of this pathogen range from 11 to 18 applications over a 9 month period.
Sulfur and Soil pH (Future Research):
Researchers at Oregon State University have also initiated work intended to balance or offset the potential detrimental effects associated with elevated rates of sulfur and iron sulfate (i.e. acidic soil conditions) on annual bluegrass putting greens, which the above treatments will likely produce.
Objectives of this research are to i) determine if sulfur applied with and without various calcium sources can reduce the number of annual fungicide applications necessary to manage Microdochium patch, ii) evaluate the effects of various sulfur applications rates applied with and without differing calcium sources on annual bluegrass health and vigor, and finally iii) explore potential correlations between soil pH, turf health and Microdochium patch incidence.
CLICK HERE for full report