Common Summer Diseases

Fungal pathogens are most detrimental to turf health from the months of May to late Septemeber (based on geographical location).  Along with the heat, irregular events and amounts of precipitation can cause huge outbreaks of disease.  Here are some of the major diseases that have superintendents pulling their hair out.

Dollar Spot:  A common disease found on most species of turf during periods of higher temperatures.  Symptoms appear as white/tan spots smaller than 6" in diameter.  On short mown turf, the spots rarely get larger than a couple inches.  Dollar spot is easily managed but can cause turf desiccation if left unchecked. 

Brown Patch:  Occurs during periods of high heat and humidity, especially when night time temps stay above 70 degrees.  The pathogen appears in turf stands as a large, brown/orange patch (some several feet in diameter).  When dew is present (or high humidity) a gray ring appears around the patch; a smoke ring.  This is where the fungus is active and is a good indicator of it's health.  While patches are large and unsightly, it is rare that brown patch will actually cause turf death.

Pythium:  Outbreaks occur during periods of extreme heat and humidity (over 90 degrees for several days combined with 90 % humidity).  The initial symptoms of Pythium are small sunken patches in an irregular pattern.  They are orange or dark gray in color.  Pythium can spread rapidly through drainage or even equipment making control of the disease difficult.  Finally, the turf will appear dark and greasy and if not treated can be fatal to the plant.

Anthracnose:  A devastating disease that occurs when areas are totally saturated for extended periods of time (heat helps the fungus but is not a necessity).  There are two types of Anthracnose, foliar and crown-rot.  Foliar effects only the leaf of the plant while crown-rot attacks the plant in its entirety.  Symptoms of anthracnose vary but may appear as yellow/orange spots or small patches (usually less than a foot in diameter) in turf stands.  Crown-rot Anthracnose is identified by dark, rotting plant structures such as the crown or roots of the turf.  It can spread quickly and is usually fatal.   

Localized Dry Spot:  A problem common in sand-based root zones.  It is a combination of little moisture and fungus activity that will actually seal off a portion of the soil from water (making the soil hydrophobic), so the symptoms appear as defined areas of wilt.  A wetting-agent is used to break up the tension between soil particles and allow water to filter through.