Bitter rot occurs only on fruit. Cankers can form on twigs, but they are rare. The fungus is one of the few fruit rot organisms that can penetrate the unbroken skin of the fruit.
The disease first appears as a small, light-brown, circular spot. One or many spots might appear; if temperatures are high, they enlarge quite rapidly and soon change to a dark brown. By the time the spots are 1/8 to 1/4 inch in diameter, they are distinctly sunken or saucer-shaped.
When they reach 1/2 inch in diameter, small, black dots–the fruiting bodies of the fungus– appear in the sunken lesion. These might be arranged in concentric rings. Later, they ooze a gelatinous, salmon-pink mass of spores, which is washed by rains onto other fruit.
Beneath the surface of the spot, the flesh is light brown and watery in a cone-shaped area, with the small end of the cone toward the fruit center. As the fruit ripens, it decays rapidly and finally shrivels into a mummy.
