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DOLLAR SPOT on Norwegian Golf Courses

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DOLLAR SPOT on Norwegian Golf Courses Risk of DOLLAR SPOT on Norwegian golf courses By Tatsiana Espevig (NIBIO, Norway), Karin Normann (Asbjørn Nyholt ApS, Denmark) and Marina Usoltseva (Botanical Analysis Group, Sweden) Popular Scientific Articles - STERF, January 2020 Photo 1. Dollar spot symptoms on a golf green. Photo: T. Espevig Risk of dollar spot on Norwegian golf courses Dollar spot was officially docu- for this disease in Scandinavia and focus of research through the projects mented in Norway in 2013 and in there is no available information on funded by STERF and other actors Sweden in 2014. In Denmark, the resistance to dollar spot in turfgrass (www.sterf.org ). disease has been seen for at least species and cultivars that are used 10 years. As far as we know, the on Scandinavian golf courses. In Dollar spot is caused by a fungus disease exists on at least 20 golf Norway (also in Denmark), the use that in 1937 was defined as Scleroti- courses in the Nordic countries. On of fungicides against dollar spot is nia homoeocarpa. After 75 years of some Nordic courses and for some not permitted, so it is important arguing that the fungus may have been years the damage from dollar spot to have knowledge and experience misplaced and where it really belongs, is severe (up to 70-80% dead grass about the most effective cultural US scientists have recently published on greens and fairways). Even in the methods against dollar spot. a scientific work showing thatS. ho- cases when disease pressure is low, moeocarpa is not a species of Scle- the diseased turf is repaired very rotinia but of Clarireedia which was slow and this leads to uneven play- introduced as a new genus (Salgado- ing surface and a significant reduc- About the disease Salazar et al., 2018). This new genus tion of the playing quality. Genetic currently consists of four species: Cla- analysis of the local dollar spot iso- Dollar spot is a common foliar disease rireedia homoeocarpa, C. bennettii, lates revealed that several of them of turfgrasses, that causes damage in C. jacksonii and C. monteithiana. All are different from those in the Uni- the United States, continental Europe four fungal species cause dollar spot ted States and that they probably and Australia (Photo 1). After dollar symptoms. Authors claim that while belong to a new species / subspecies. spot was officially documented in Nor- C. bennettii occurs primarily on red There is little knowledge of environ- way and Sweden (Espevig et al. 2015, fescue (C3 grass) and appears to be mental conditions that is beneficial 2017), the disease has been in the 2 restricted to the United Kingdom, C. The Swedish student Anita Ejderdun Norwegian isolate. The growth rates jacksonii and C. monteithiana occur in previously worked with dollar spot of isolates from Denmark, Sweden a variety of C3 and C4 grass species isolates which were collected from and UK were reduced by an average and appear to be globally widespread. the Nordic countries. Among other of only 28% when compared to their Earlier experiments at NIBIO, using things, she looked at the ability of dol- growth at 16 °C prior to chilling. It DNA analysis, showed that the Scan- lar spot to attack creeping bentgrass appears that the lack or low inhibition dinavian isolates (fungal samples) of at 6 ° C, 15 ° C and 24 ° C in a pot in growth for several isolates could the dollar spot belonged to two genetic trial. Surprisingly her study shows that indicate a potential for enhanced groups: one group consisting of the the fungus samples tested were more survival during cold winter condi- Danish and most Swedish isolates was active at 6 ° C and / or 15 ° C than at tions but further work is necessary to identical to the one from the East and 24 ° C (Ejderdun, 2015). confirm this. Midwest in the United States, namely C. jacksonii while the other group The recent laboratory study which was Rolling as an consisting of the Norwegian and some conducted at NIBIO’s laboratory at Swedish isolates differed. Already Landvik in the fall of 2017, showed important preventive then, we thought that this other group that all tested dollar spot isolates from measure against could be a separate species or sub- different countries (1 from Denmark, species. And now that we know that 1 from Norway, 3 from Sweden, 4 dollar spot dollar spot can be caused by different from the United States and 2 from Rolling is known to reduce dollar fungal species, we should find out the UK) had 24 ° C as the optimum spot (e.g. Giordano, 2012). In the where our local isolates belong and temperature for growth as pure culture new STERF dollar spot project we which Clarireeda spp. we have in the in Petri plates (Entwistle et al., 2018). tested the effect of rolling on greens Nordic countries. The maximum growth temperature for on two golf courses in Denmark, most isolates in this study was bet- two in Sweden and one in Norway. ween 32 and 40 ° C which was higher Dollar spot can grow The results from Sweden are very than previously reported by Bennet strong and show that regular rolling and attack grass at (1937). Minimal temperature for in the growing season from June to fungal growth was between 0 and 2 ° low temperatures September 2017 reduced dollar spot C and all fungal isolates could regrow significantly. On average, for August- after being at 0 ° C for 3 weeks. No A common assumption for many years September 2017, the dollar spot was reduction in growth rate was recorded has been that dollar spot cannot be in reduced 61% by rolling 2 times per for either the USA isolates collec- the Nordic countries as it requires a week and 95% by rolling 4 times per ted from cool-season grasses, or the warmer climate. week on a pure fine fescue golf green Photo 2. Rolling 4 and 2 times per week from June to September reduced dollar spot by 95% and 61% respectively as compa- red with the control (no rolling) on a fine fescue golf green in Vallda GC, September 7, 2017. Photos: Stefan Nilsson. 3 Photo 3. Lab screening of turfgrass species and cultivars for resistance to dollar spot isolates of different origin. Photos left and middle by Tatsiana Espevig and photo right by Ove Hetland. in Vallda GK (Photo 2). In Roskilde (Dernoeden, 2000). In our dollar spot among turfgrass species and culti- GK in Denmark, on a foregreen with project, N effect was tested on one vars. It is also a question whether the a mixture of fine fescue and colonial Danish, one Swedish and one Nor- different Nordic isolates are equally bentgrass dollar spot was reduced wegian golf course. In Drammen GK aggressive as American or British 37% by rolling 2 times per week and (Norway), dollar spot did not develop isolates and whether there are any 54% by rolling 4 times per weeks on in summer 2017 or 2018. In 2017, the differences among the Nordic isola- average for September and October, effect of N was not statistically sig- tes. In the spring of 2018, 20 of the however the reduction was not statis- nificant at Helsingør GK in Denmark most widely used grass species and tically significant. In 2018, dollar spot and at Kävlinge GK in Sweden. In cultivars were tested for resistance did not develop on these experimen- 2018, we got 24% less dollar spot on to 10 different dollar pot isolates tal golf greens most likely due to an a creeping bentgrass green in Käv- from Norway, Denmark, Sweden, the extreme dry summer. Nevertheless, linge GK by increasing the amount of United Kingdom and the United States even during dry summer rolling can nitrogen from 150 to 240 kg ha-1 kg in the laboratory at NIBIO Landvik be recommended for use with great per year. However, in March 2019 on (Photo 3). This experiment was carried advantage. Rolling will also improve the plots, which received 240 kg N out at temperatures equivalent to a ball roll on greens and contribute to an ha-1 in 2018, the microdochium patch Norwegian summer with 16 ° C night increase in soil moisture (dollar spot is incidence was 30% vs. 14% on the and 21° C day. The preliminary results known to thrive best when combined plots which received 150 kg N ha-1. show that in average for all isolates with dry soil and a lot of moisture on Thus, it is impossible to draw unam- the rankings of the species’ resistance the foliage (Smiley et al., 2005). biguous conclusions about the advisa- to dollar spot were as follows (from bility of using increased doses of N to most to least resistant): ryegrass > red Nitrogen (N) fight dollar spot on golf greens which fescue ≥ Kentucky bluegrass ≥ vel- are exposed to microdochium patch vet bentgrass ≥ creeping bentgrass & fertilization during winter time. colonial bentgrass & annual bluegrass. There was a big variation among the From previous studies in the USA cultivars especially of colonial bent- where dollar spot has been studied Resistant turfgrass grass and Chewings fescue. The most for at least 50 years, it is known that species and cultivars aggressive isolates were one from the this disease can become more severe United Kingdom and two from the with low N fertilizer (Landschoot and Dollar spot affect all turfgrasses but United States, while the weakest were McNitt, 1997) and low cutting height the resistance to dollar spot varies the Norwegian and the other from 4 the United Kingdom; isolates from STERF for such an evaluation.
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