Dollar Spot on Putting Greens EP-131 Megan Kennelly Plant Pathologist Symptoms Disease development is favored by high relative Dollar spot is caused by the fungus Sclerotinia homoeo- humidity and extended periods of leaf wetness. The tem- carpa. It develops throughout the growing season. In Kansas perature range for growth is approximately 60 to 85 degrees it is most common in spring through early summer and Fahrenheit. Dry soils and poor nitrogen fertility also con- again in late summer through early fall. In putting greens or tribute to increased disease severity. low-cut turf, the disease appears as sunken patches of tan-to- brown turf up to 2 inches in diameter (Figure 1). On dewy Control mornings, white, cobwebby fungal growth is sometimes Several bentgrass cultivars (Crenshaw, SR 1020) are visible on the turf (Figure 2). The fungal growth disappears very susceptible to dollar spot and should not be used for as the turf dries. In severe cases, the infection spots coalesce fairways or seeded on putting greens prone to the disease. Consider using cultivars, such as L-93, that are moderately to form larger blighted areas (Figure 3). resistant. Conditions Several cultural practices will help suppress dollar The pathogen survives in infected plants and debris. spot. Minimize leaf wetness duration by physically remov- The dollar spot fungus does not produce spores. It is spread ing dew (poling, mowing, syringing) in early morning, in infected debris by water, wind, equipment, shoes, etc. and avoid early evening watering. Do not allow the grass to undergo drought stress. Maintain adequate nitrogen fertility. Some turf managers have recommended biological control of dollar spot by fertilization with compos- ted turkey litter, bovine wastes, and other organic amendments. However, organic fertilizers have not been consistently proven to reduce dollar spot in university research trials. Similarly, the addition of microbial biological control agents (fungi and bacteria) has not been proven consistently to reduce dollar spot. Recent studies at Kansas State University found no dollar spot reduction with amendments of calcium silicate. Figure 1. Discrete dollar spot infection centers on creeping bentgrass. Kansas State University Agricultural Experiment Station and Cooperative Extension Service Preventive fungicide applications at 7- to 28-day tion and increase of fungicide-resistant strains of dollar intervals may be necessary to suppress dollar spot. spot. Resistance has been reported in other states of to Timing and frequency of application depends on weather these fungicide groups. Golf course superintendents should conditions and on the type of fungicide that is applied. consider limiting the number of applications of these Continuous use of certain systemic fungicides, includ- fungicides during the growing season and alternating these ing thiophanate methyl, iprodione, and the DMI (sterol products with contact fungicides not prone to resistance demethylation inhibitor) fungicides (such as triadimefon, problems. Always follow label instructions, which may propiconazole, and myclobutanil) may result in the selec- include resistance management. Figure 2. White fungal growth (mycelium) can be seen on dewy mornings. Figure 3. Coalescing spots on creeping bentgrass (courtesy Kevin Mathias, Bugwood.org). Fungicides labeled for dollar spot on putting greens. Typical application Active ingredient Fungicide groupa Efficacy and notes interval (days) Examples of products Bacillus licheniformis Biocontrol agent good 3-14 EcoGuard boscalid carboximide good to excellent 14-28 Emerald Daconil Ultrex, Manicure, chlorothalonil chloronitrile good to excellent 7-14 Concorde SST, Chlorostar, Echo, Pegasus L copper hydroxide + Copper + EBDC limited data available 7-14 Junction mancozeb good to excellent, fenarimol DMI 10-30 Rubigan at risk for resistance hydrogen dioxide oxidizing agent inconsistent, sometimes fair 7 Zerotol good to excellent iprodione dicarboximide 14-28 Chipco 26GT, Chipco 26019 at risk for resistance Fore, Protect T/O, Protect D/F, mancozeb EBDC inconsistent, sometimes fair 7-14 Dithane, Mancozeb excellent, myclobutanil DMI 14-28 Eagle at risk for resistance excellent, propiconazole DMI 7-28 Banner MAXX, Spectator at risk for resistance QoI pyraclostrobin Good b 14 Insignia (strobilurin) Cleary’s 3336, Fungo, Proturf excellent, thiophanate-methyl benzimidazole 10-21 Systemic Fungicide, Systec 1998, at risk for resistance Cavalier, T-Storm thiram dithiocarbamate fair, inconsistent 7-10 Spotrete, Thiram, Defiant triadimefon DMI excellent 14-30 Bayleton, Proturf Fungicide VII Trichoderma Biocontrol agent fair, inconsistent 7-14 Bio-trek harzianum vinclozolin dicarboximide excellent 14-28 Curalan, Touche, Vorlan a Fungicide group abbreviations: EBDC = ethylene bis-dithiocarbamate, DMI = demethylation inhibitor (sterol inhibitor) b In trials at other universities, pyraclostrobin provided moderate dollar spot suppression. However, in a recent test at Kansas State University , plots treated with pyraclostrobin developed more dollar spot than the untreated plots. Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer. Publications from Kansas State University are available on the World Wide Web at: www.oznet.ksu.edu Contents of this publication may be freely reproduced for educational purposes. All other rights reserved. In each case, credit Megan Kennelly, Dollar Spot on Putting Greens, Kansas State University, October 2007. Kansas State University Agricultural Experiment Station and Cooperative Extension Service EP-131 October 2007 K-State Research and Extension is an equal opportunity provider and employer. Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30, 1914, as amended. Kansas State University, County Extension Councils, Extension Districts, and United States Department of Agriculture Cooperating, Fred A. Cholick, Director.
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