Photo: Dollar spot disease on a fairway on a Danish golf course. Photo: Karin Normann
Dollar spot (DS) damage in Scandinavia varies, but can give 70-80% dead turf on greens and fairways. This project aims to reduce spread of DS in the Nordic countries and develop non-chemical control measures, in three work packages:
WP1. In summer 2017, on golf greens with red fescue (Vallda GC) and foregreens with red fescue, colonial bentgrass and annual bluegrass (Roskilde GC), rolling 2 times/wk reduced DS by 61% and 37% and rolling 4 times/wk reduced DS by 95% and 54%, respectively. In 2018 (very dry summer), DS did not develop on these greens. At Kävlinge GC, N had no effect in 2017 on a creeping bentgrass golf green. In 2018, increasing annual N from 150 to 240 kg ha-1 reduced DS by 24% (from 100 to 76 infection centres/m2), but increased microdochium patch incidence to 30% in March 2019 (14% on plots which received 150 kg N ha-1). Thus, no firm conclusions can be drawn about using high N rates to fight dollar spot on golf greens with microdochium patch in winter.
WP2. In autumn 2017, all Scandinavian isolates of Clarireedia spp. had optimal temperature for growth (OGT) of 24°C, while USA isolates had 16°C and 24°C as OGT. 0°C and 40°C reduced growth of all isolates by ~100%. After 3 wk at 40°C, all isolates died. After 3 wk at 0°C, growth of Scandinavian isolates and British isolates was reduced by 7-36% and 23-38%, respectively, with no reduction in USA and Norwegian isolates. This indicates potential of some isolates for winter survival.
WP3. In spring 2018 and 2019, 20 common turfgrass species and cultivars were tested for resistance to 10 different isolates from Norway, Denmark, Sweden, UK and USA in the lab at NIBIO Landvik (Photo 1). The most aggressive isolates to date are one Clariredia sp.
from UK and two from USA (C. jacksonii and C. monteithiana). The weakest isolate is C. jacksonii from Norway. C. jacksonii isolates from USA appear more aggressive than those from Sweden and Norway. However, based on the data, we cannot conclude that aggressiveness
in Clarireedia spp. is species-specific, as that of C. jacksonii isolates varied between turfgrass species and varieties (cultivars of perennial ryegrass and slender creeping red fescue were generally most resistant).
There was great variation among cultivars of chewings fescue, colonial bentgrass and creeping bentgrass. On average for the five Nordic DS isolates, velvet bentgrass and Kentucky bluegrass had significantly higher resistance than creeping bentgrass and annual bluegrass.
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)