Its that time of year when I begin to see people putting preventative strategies in place for Dollar spot - so I thought it was worth going back to basics.
What is it?
Dollar spot can be identified easily by the lesions on leaves, they are a pale, bleached colour. They are bound at either end by a darker reddish-brown band separating the affected tissue from the healthy green tissue.
It evolves into Small (dollar size) spots of bleached turf occur on close mown grass. The spots may coalesce to form large areas of affected turf. White mycelium may be present on affected areas on dewy mornings, which disappear as the leaves dry.
Where is Dollar Spot found?
Any area of turf, especially golf greens, tees, fairways and bowling greens. In the UK, fescue dominant swards are at high risk of infection. Poa annua grass can also be severely affected.
When is Dollar Spot likely to attack turf?
During the summer months, when the daytime temperatures are above 20ºC. Humid or thundery conditions can encourage an outbreak, as can heavy dews. Low fertility swards are at more risk from Dollar Spot.
The Smith-Kerns model is a great tool to help predict damage and times to treat.
Historic pressure periods can also be identified using the Greencast historic disease tool (link here ...)
Effects of Dollar Spot
The spots reduce the aesthetic appearance of fine turf, such as golf greens and create an uneven surface causing non-uniform ball roll. On longer cut areas, such as tees, playability may not be affected (unless the outbreak is very severe) but the aesthetic appearance will be reduced.
High Risk Situations
- Heavy morning dew.
Daytime temperatures 20ºC and above. - Low fertility situations.
- Excessively low cutting heights.
- High humidity
- Fescue dominant sward, although there is variation among subspecies and cultivars. Poa annua grass is also susceptible.
- Slowly growing turf.
- Moisture retentive turf surface.
Integrated Turf Management
- Dollar spot can be more severe when the surface is moist but the underlying soil dry. Therefore, irrigation should be infrequent and to the depth of the rootzone. Air movement over the surface should be encouraged.
- Dollar spot is more prevalent under low fertility, especially nitrogen. Therefore, adequate fertiliser should be applied to prevent low nutrition occurring.
- Soil compaction and the presence of thatch layers have also been shown to promote dollar spot. Regular aeration will reduce compaction and encourage the removal or breakdown of any thatch layer reducing the potential for severe outbreaks.
- Look to overseed with more resistant cultivars
- Regularly look at GreenCast to identify periods of high risk.
Fungicidal Control
Instrata Elite is very effective on Dollar Spot and preventative applications should be targeted around warm humid periods of the Summer.
You might also be interested in my blog on Managing Dollar Spot in Turf Grass here.
