Fusarium Patch of Turf

Microdochium nivale

Other names: Fusarium nivale, Gerlachia nivalis

Description:

A fungal disease of turf grasses.

Species Affected:

Turf and lawn. Poa, Agrostis and Bentgrass.

Biology:

Tends to be worse when conditions in spring are wet and cool.
Requires more than 10 hours of leaf wetness for infection.
Active when temperatures are between 1 and 15 0C.
The fungus produces an enzyme to break down plant cells which gives the water soaked leaf symptoms and tissue collapse. When the disease is not active (usually as temperatures rise) the affected leaves are straw coloured.
The fungus survives in soil, thatch and plant debris.
Avoid traffic from infected to clean areas.

Life Cycle:

Spores germinate in cool wet conditions and infect the plant if the leaf remains wet for more than 10 hours. The fungus grows and destroys cells leaving a water soaked leaf and collapsed tissue. As temperatures rise above 15 0C the fungus stops growing and infected leaves usually turn yellow. Spores are produced a few weeks after infection.

Origin and History:

Mercurial and benomyl fungicides were used previously but are no longer available.
Iprodione, thiophanate-methyl and propiconazole resistant strains have been reported.

Distribution:

Canada, New Zealand.

Significance:

The incidence has increased with the reduction in the use of mercury based fungicides.
Serious disease of turf especially Poa species.
It often defoliates plants but only rarely infects the crown and kills plants.

Management and Control:

An integrated control strategy is usually required.
Remove dew from turf by mowing, dragging a hose across turf or irrigating just before dawn.
Increase exposure to morning sun and wind.
Improve drainage and reduce thatch to reduce humid microclimates.
Top dress with sand frequently.
Avoid heavy nitrogen applications. Maintain adequate K applications. Adjust pH to suit turf species. Fusarium patch is often reduced under acid conditions. Use sulphur or ammonium sulphate to decrease pH.
Monitor regularly for small (1-2 cm ) patches of collapsed, water soaked, olive coloured leaves and apply fungicides before spores are formed. Fungicides applied in autumn may appear to be ineffective but they protect spring growth from new infections.
Chlorothalonil, Iprodione, propiconazole thiophanate-methyl, quintozene, thiabendazole and thiram fungicides have action on the disease. Rotate between fungicide groups to reduce the risk of developing resistance.
Apply fungicides when cool wet conditions are forecast and there has been a history of the disease or when symptoms are first noticed.
Control highly susceptible weed species like Poa annua.

Related and Similar Species:

Often confused with Dollar Spot (Sclerotinia homeocarpa) or Brown Patch (Rhizoctonia spp.).

References:

MacDonald, L. (1999) Fusarium Patch. GreenMaster 34(1).

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.HerbiGuide.com.au for more information.