Risk assessment, management and control of dollar spot caused by Clarireedia spp. on Scandinavian golf courses

Summary

The field trials and laboratory experiments were competed in 2019. In 2020, two popular science articles were produced, in English and Scandinavian languages, a scientific manuscript from WP3 was submitted to ITSRJ, and a final report and two videos were produced. Thus, the project summary below is the same as in 2019. The aim of this project is to reduce the spread of dollar spot in the Nordic countries and to provide the golf sector and greenkeepers with non-chemical measures for control of this disease. Dollar spot (DS) was officially documented in Scandinavia in 2013. The damage from DS in Scandinavia varies and can be up to 70-80% dead turf on greens and fairways. The project consisted of three work packages (WP):

WP1. In summer 2017, on golf greens with red fescue (Vallda GC) and on foregreens 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. In 2018, DS did not develop on these golf greens, most likely due to an extremely dry summer. At Kävlinge GC, the effect of N was not significant in 2017 on a creeping bentgrass golf green. In 2018, an increase in the annual N amount from 150 kg ha-1 to 240 kg ha-1 reduced DS by 24% (from 100 to 76 infection centres per m2). However, in March 2019 on the plots which received 240 kg N ha-1 in 2018, the microdochium patch incidence was 30%, vs. 14% on the plots which received 150 kg N ha-1. Thus, it is impossible to draw unambiguous conclusions about the advisability of using increased rates of N to fight dollar spot on golf greens which are exposed to microdochium patch during winter time.

WP2. As determined in autumn 2017, all Scandinavian isolates of Clarireedia spp. had 24 °C as the optimal temperature for growth (OGT), while isolates from US had both 16 °C and 24 °C as the OGT. Both 0 °C and 40 °C reduced growth of all isolates by almost 100%. After 3 wk at 40 °C, all isolates were dead. After 3 wk at 0 °C, the growth of Scandinavian isolates and British isolates was reduced by 7-36% and 23-38%, respectively, while there was no reduction in American and a Norwegian isolate. This indicates certain potential of the isolates for winter survival.

WP3. In spring 2018 and 2019, 20 widely used turfgrass species and cultivars were tested for resistance to 10 different Clarireedia isolates from Norway, Denmark, Sweden, UK and US in the laboratory at NIBIO Landvik (Photo 1). The preliminary results show that the most aggressive isolates were one Clariredia sp. from the UK and two from the USA (C. jacksonii and C. monteithiana), while the weakest isolate was C. jacksonii from Norway. Clarireedia isolates from Denmark and Sweden were intermediate. It appears that C. jacksonii isolates from USA are more aggressive than those from Sweden and Norway. However, based on the current data, we cannot conclude that aggressiveness in Clarireedia spp. is species-specific, as the aggressiveness of C. jacksonii isolates varied in different turfgrass species and varieties. Generally, cultivars of perennial ryegrass and slender creeping red fescue were the most resistant. There was great variation among the 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.

Fundings (kSEK)

Project participants

Tatsiana Espevig

Researcher

Norwegian Institute for Bioeconomy (NIBIO), Department for Urban Greening and Environmental Technology, Turfgrass Research Group, Landvik, Reddalsveien 215, 4886 Grimstad, Norway.

+47 406 23 778

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