The Causal Pathogen
The causal pathogen of Dollar Spot is known as Sclerotinia homeocarpa. Microscopic diagnosis of Dollar spot is undertaken via its distinctive granulated hyphae which appears after a period of incubation.
The disease is characterised by round, bleached out / straw coloured spots ranging in size from a few centimetres to several centimetres. The spots appear as sunken turf. Individual spots coalesce and destroy turf in large areas. Recovery from severe dollar spot can be extremely slow. With dew, greyish white, fluffy mycelium can be observed in the mornings.
When the diseased spots have progressed to bleached straw like stage, dollar spot lesions called 'stroma' can be found on leaves. These lesions are shaped like an hour glass
The Dollar spot fungus overwinters in the form of sclerotia and as dormant mycelium in plant crowns and roots of infected plants. The sclerotia appear as tiny, thin black flakes. Research conducted by Mills & Rothwell established that Dollar Spot Infection was high when maximum ambient temperatures are above 25 Degrees Celcius and Maximum relative humidity is greater than 90% during any 3 days in 7.
Cultural Control Methods
Low nitrogen levels intensify Dollar Spot damage. During periods of severe dollar spot infection, the nitrogen levels should be increased. Tank mixing Dollar Spot fingicides with a nitrogen source can be a useful strategy. Light and frequent Nitrogen applications is most efficient.
Removing dew or guttation water is a common practice on golf course greens which may assist in limiting dollar spot infection.
Chemical Control Options
Chemical control options are highlighted below;
Tebuconazole / Trifloxystrobin – eg. Dedicate.
Propiconazole – eg. Banner Maxx.
Azoxystrobin / Propiconazole – eg. Headway Maxx.
Chlorothalonil / Fludioxynil / Propiconazole – eg. Instrata.
Trifloxystrobin / Iprodione – eg. Interface.
Thiram – eg. TMTD 600
Prochloraz – eg. Protak
Thiabendazole – eg. Vorlon