Fungal diseases usually occur in the lawn when conditions are damp and the strength of the grass is low. The appearance of fungus is probably the most common symptom of “run-down” turf arising from such causes as over compaction of soil, nutrient and pH imbalance, inadequate drainage, poor soil aeration, dense shade, over close mowing and a shallow depth of topsoil. The eradication of fungal diseases can only be achieved effectively when the cause can be correctly identified and conditions rectified. The removal of the cause results in a slow disappearance of the fungus and prevention of its return. Attention to general maintenance such as the improvement of drainage, the application of fertiliser to improve the turf quality and aeration will have obvious benefits.
The most common types are:
Either toadstools or an outline of a cloud shape and the outline is darker green than the rest of the lawn.
It appears as small freckles across the lawn about the size of a 50 cent piece.
Originally found in Bentgrass (USA) where it formed spots the size of silver dollars, consequently the name “dollar spot”.
Infected areas 10 cm or larger may run together, causing great patches of dollar spot over the turf area. Irregular patches to 3 metres wide
Dollar spot fungi can be spread by mowers, feet, hoses, travelling sprinklers and other maintenance equipment.
May be active from late spring to late autumn.
Most problems develop when temperatures are tolerably warm and change rapidly, as with warm days and cool nights.
Heavy layers of a thatch can encourage Dollar Spot because water, air and nutrients cannot penetrate to the underlying soil and grass roots. This results in shallow and poorly developed roots that are highly susceptible to drought stress.
- Affected leaves will show yellow-green blotches or bands that generally can go undetected. These lesions gradually bleach to a white or straw colour.
- On finer-textured turf grasses, individual lesions on the leaves often bridge the width of the grass blade, producing a constricted area resembling an hourglass. On coarser grasses, the spots caused by dollar spot may not span the blade.
- The tip of the leaf blade may show the characteristic lesion, or the lesion may be in the middle of the blade, leaving the leaf tip green.
- When the turf grass is wet from early morning dew, a fine, white cobweb-like mycelial growth (strands of fungus) may be visible on the diseased leaves. As the grass dries out the mycelium disappears. Be sure not to confuse this with spider webs.
- Spray the lawn area with Mancozeb, (available in our Lawn Shop) plus twice more at 6 day intervals if you notice Dollar Spot. Please follow directions.
- Cut the lawn at least once every 6 days.
- Lawn under stress is more susceptible to infection. Water during daylight hours preferably in the morning
- Keeping your equipment clean will help prevent the fungi from spreading
- If watering very late in the day, leave enough time for grass blades to dry after watering before nightfall arrives
- Early morning watering (before sunrise) helps remove dew from the leaf surface
- Never water the lawn in the late afternoon or at night as this enhances the growth disease
- Proper lawn management, such as aeration, proper watering and fertilization, will reduce Dollar Spot problems
- Use fungicides only in situations with recurrent Dollar Spot problems
- Ensure nitrogen levels are sufficient to sustain a moderate rate of shoot