Question
We live in Escondido - 40 miles NE of San Diego - hot climate. We planted Marathon Sod last year and frequenelty we get these large clumps of white stuff on the back lawn. They look like mushrooms until you get up close - when you disturb them they send out a black dust - definitely doesn't look healthy, although the lawn is doing well. Is this a mold, a fungus or what? We have struggled with getting the right level of watering in the heat we experience here.  

Answer
i'm in southern NJ. sounds like a fungus. the dust things are called spores. that is how they reproduce. you should only water when it is necessary. many people kill their lawn by watering improperly. water in the AM so the turf can absorb the water rather than have it all evaporate(that is what normally happens during the heat of the day). apply 1" or more at a time. you can water later in the day also. don't water towards evening or the turf will not dry sufficiently before darkness. this creates fungus and mold problems.
mushrooms can be a sign of too high soil acidity. adding turf lime can buffer(raise the soil pH back towards neutral pH)
check w/your garden center/nursery for good local advice.
good luck
rick
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