Photo: Dollar spot disease on a fairway on a Danish golf course. Photo: Karin Normann
Dollar spot (DS) was officially documented in Scandinavia in 2013 and today is present on more than 20 Nordic golf courses. Damage from DS in Scandinavia varies and can be up to 70-80% dead turf on greens and fairways. Even when the disease pressure is low, recovery from DS is very slow and the damage leads to indents on the green surface and significant lowering of playing quality. The aim of this project is to reduce the spread of DS in the Nordic countries and to provide the golf sector and greenkeepers with non-chemical measures for control of this disease. The project consists of three workpackages (WP):
WP1. In summer 2017, on golf greens with red fescue (Vallda GC) and with red fescue, colonial bentgrass and annual bluegrass (Roskilde GC), rolling 2 times per wk reduced DS by 61% and 37% and rolling 4 times per wk reduced DS by 95% and 54%, respectively. Dollar spot did not develop on these experimental golf greens in 2018, most likely due to an extreme dry summer. Increasing N dose from 150 to 240 kg ha-1 yr-1 reduced DS by 24% on a red fescue/annual bluegrass green in Kävlinge GK in 2018 (Fig. 1).
WP2. In autumn 2017, all local isolates of Clarireedia spp. had 24 °C as the optimal temperature for growth (OGT), while isolates from the US had both 16 °C and 24 °C as OGT. Both 0 °C and 40 °C reduced growth by almost 100%. After 3 wk at 40 °C, all isolates were dead. After 3 wk at 0 °C, growth of Scandinavian and British isolates was reduced by 7-36% and 23-38%, respectively, with no reduction in an American and a Norwegian isolate. This indicates certain potential of the isolates for winter survival.
WP3. In spring 2018, 20 widely used turfgrass species and cultivars were tested for re-sistance to 10 different isolates from Norway, Denmark, Sweden, UK and US in NIBIO laboratory at Landvik (Fig. 2). The incubation temperatures were 14 °C night and 19-20 °C day. Preliminary results show the following ranking of resistance in turfgrass species (from most to least resistant): ryegrass > red fescue ≥ Kentucky bluegrass ≥ velvet bent ≥ creeping bent & colonial bent & annual bluegrass. There was great variation in resistance among the cultivars and in aggressiveness of the isolates. The most aggressive isolates were one from UK and two from the US, the weakest was from Norway and the second weakest from UK (isolates from Denmark and Sweden were intermediate). The experiment will be repeated in 2019.
Myntflekk var offentlig dokumentert i Norden i 2013, og så vidt vi vet, finnes sykdommen på minst 20 golfbaner i Norge, Sverige og Danmark. På noen golfbaner og i noen år er skadene fra myntflekk alvorlige (opp til 70-80% dødt gress på greener og fairways). Og selv om sykdomstrykket er lavt, fører de syke flekkene til store ujevnheter på spilleoverflaten og derfor til reduksjon i spillkvalitet. I tillegg repareres skader fra myntflekk sakte. Genetisk analyse av de lokale isolater av Sclerotinia homoeocarpa viste at flere av dem er forskjellig fra de i USA og de, sannsynligvis, tilhøre en ny art / underart. Det er ingen tilgjengelig kunnskap om resistens i gress mot de lokale isolater av S. homoeocarpa og om skjøtsel mot myntflekk i Skandinavia. Og det er lite kunnskap om miljøforhold som er gunstig for denne sykdommen i Skandinavia.
Tatsiana Espevig, Researcher (PhD), NIBIO - The Norwegian Institute of Bioeconomy Research, Reddalsveien 215, 4886 Grimstad, Norway Tel: +47 406 23 778. E-mail email@example.com
• To find the most efficient frequency for rolling and nitrogen rate in dollar spot control on golf greens (WP1)
• To determine the cardinal temperatures for growth of Scandinavian isolates of S. homoeocarpa and to assess risk of the pathogen spreading in Scandinavia (WP2)
• To screen the most widely used turfgrass species and cultivars for in vitro resistance to the Scandinavian isolates of S. homoeocarpa (WP3)