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Dollar Spot

Dollar Spot
Caused by: Sclerotinia homoeocarpa F. T. Bennett

 

 Plate 1: Dollar Spots on Poa annua

Description
Dollar Spot lesions on leaves 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. Small (dollar size) spots of bleached turf occur on close mown grass (Plate 1). The spots may coalesce to form large areas of affected turf (Plate 2). White mycelium may be present on affected areas on dewy mornings, which disappear as the leaves dry.

Plate 2: Dollar spots coalescing

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

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.
  • Fescue dominant sward, although there is variation among subspecies and cultivars. Poa annua grass is also susceptible.
  • Slowly growing turf.
  • Moisture retentive turf surface.
  • ITM Solutions

Integrated Turf Management

  • Dollar spot can be more severe when the sward surface is moist but the underlying soil dry. Therefore, irrigation should be infrequent and to the depth of the rootzone. Air movement over the sward 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.
  • Regularly look at GreenCast to identify periods of high risk.

Fungicidal Control
The following product has label recommendation for Dollar spot control in the UK:

 Parameter

Banner Maxx

Mode of action

Systemic

Optimum timing

At first sign of disease

Dose rate

3.0 l/Ha

Water volume

400 to 1000 l/Ha

LERAP

N/A

Suggested Programme
Once conditions conducive to dollar spot occur, or Greencast indicates high risks of disease a preventative application of Banner Maxx should be applied.