In the Netherlands, golf is increasing in popularity and the present golf courses are occupying 7300 hectares in total (Zibb: Portal voor ondernemers. Tips, tools en het laatste nieuws). Turf grasses are plants that are made very susceptible to infection by fungi because of their prerequisites. Especially the greens have high demands: The grass should be kept very short and has to form a smooth surface with as little unevenness as possible. Every time the grass is mowed, the plants are mechanically wounded and are therefore more easily penetrated by fungi. Throughout the year, turf grasses are dealing with a lot of different fungi, which all have a different ideal combination of factors to infect the grass.
Sclerotinioria homoeocarpa or Dollarspot and Microdochium nivale or Snow Mold are the most common fungi and cause severe infections of greens.
Dollarspot occurs from early spring till late autumn over the whole world. Many species of turf grasses are susceptible to these fungi. We this fungus infects the grass, small, circular, straw coloured spots occur. These can reach a width of 15 cm (Couch, 3th edition). The fungus can be spread by human, animals, wind and water and gets active when dew occurs on the edge of the grass. Wet leaves also favourable for the fungus. (Smiley et al, 3th edition).
Snow mold can occur in every month of the year and doesn’t exactly need a snow cover in order to be present. This fungus grows in cold and humid weather conditions. In autumn and winter, when the grass doesn’t grow as fast or not at all, it is extremely susceptible to snow mold (Smiley et al, 3th edition).
Many fungicides are used by golf keepers, but these are costly and often environmental damaging substances. Moreover, fungicides can only be used in restricted amounts in order to avoid that the fungi adapt genetically to and detoxify those chemicals. Making use of resistant cultivars is another approach but is not durable, because fungi can adapt themselves easily and their resistance is mostly broken within a few years.
UV light can damage and kill many micro organisms (figure 1). From research done by Wageningen University, it was proven that UV-C light can reduce the germination of spores of Phytophthora infestans (Kessel and Förch, 2006). Analogous, this would be also suitable for Sclerotinioria homoeocarpa and Microdochium nivale.
Figure 1. The effect of UV light on the DNA of living organisms. When the applied dose is high enough, the DNA helix is destroyed or gets damaged, so in the end, the DNA is dysfunctional. (American Air & Water®, Inc. - UV Disinfection Systems).
With field trails, we want to test if a daily applied dose of UV light will reduce the symptoms of Dollar spot and snow mold.
The field trials that are described in this report were conducted in October 2007 on a green of a golf court in Geijsteren and in November 2007 in Andersteijn. The green keepers cooperated by applying the UV light daily on the test plots of the greens. The Greens-Cleaner was put behind a gator and a few minutes before the treatment the lamps were turned on in order to function properly. The dose of UV we applied was ….. , determined by former experiments …
Field trial in Geijsteren (Dollarspot)
Set up of the field trial
The first trial was done on a green in Geijsteren, the Netherlands, where symptoms of Dollarspot could be clearly distinguished (figure 2). This trail was mainly conducted to determine the optimal duration of UV application: long enough to reduce the symptoms of the fungus, but not too long in order not to damage the grass.
Figure 2. Symptoms of Dollarspot on the green in Geijsteren.
In this trail, 7 plots of equal size were marked. UV light was daily applied by the green keeper on 6 plots during two...