Both diseases are caused by fungi that inhabit the soil or survive in infected plant debris. Green fruit as well as ripening and harvested fruit are attacked by the gray mold fungus. Infection starts when pathogen spores are blown or splashed onto fruit during wet, humid weather coupled with moderate temperatures. Infection quickly spreads to other fruits touching the rotten fruit. Affected tissue turns light brown and often becomes covered by a velvety gray mold on the fruit surface.
Affected fruits retain their shape but become tough and dry.
In Nebraska leather rot is a sporadic disease that occurs during the growing season when wet warm weather occurs. Like gray mold it affects fruit of all ages. The pathogen is a soilborne fungus, and its spores are spread to fruit by splashing rain or by direct contact with the ground. Infected ripe fruit appear dull and lifeless and have a bleached to reddish-purple to brown color. Their texture is tough, and they have a decidedly bitter taste.