EP131 Dollar Spot on Putting Greens by ghkgkyyt


									            Dollar Spot on Putting Greens

                                                           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).
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
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.
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
                                                          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
myclobutanil                 DMI                                                                           14-28            Eagle
                                                          at risk for resistance
propiconazole                DMI                                                                            7-28            Banner MAXX, Spectator
                                                          at risk for resistance
pyraclostrobin                                            Good b                                             14             Insignia
                                                                                                                            Cleary’s 3336, Fungo, Proturf
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
                             Biocontrol agent             fair, inconsistent                                7-14            Bio-trek
vinclozolin                  dicarboximide                excellent                                        14-28            Curalan, Touche, Vorlan
 Fungicide group abbreviations: EBDC = ethylene bis-dithiocarbamate, DMI = demethylation inhibitor (sterol inhibitor)
 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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