Question
I noticed several years ago a collection of small golf-ball sized (and shaped) molds growing in the lower part of our front yard.  They cluster together.  When stepped on they emit a powdery substance.  I dug 3 of these clusters out of my lawn last year.  This year I have found four or five of these growths in the lawn (i.e., the quantity is increasing each year).

The growth goes about 3-4 inches into the ground.  These are not like mushrooms.  They grow in the ground and eventually protrude through the dirt and grass.

How can I treat my lawn so that I kill the molds I have now and prevent any others from starting?

Answer
Jeremy:

The mushrooms you describe sound like puffballs.  If puffballs, they are not poisonous.

You may try a few cultural techniques to get rid of them.  Aerate deeply and apply nitrogen lightly, as you would for a lawn fertilization.  Thatch if the turf has a deep layer of dead leaves.

Prevention is almost impossible, since the spores (seed) are airborne and come from miles away.  There may be some decaying matter below or on the soil surface on which the organism is feeding.

Other than appearance, these pose little problem.

Best wishes.