Colletotrichum acutatum J.H. SimmondsColletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz.
Distribution: Common to all fruit-growing regions in eastern North America. It is an important fruit rotting disease in warmer apple growing regions, such as the mid-Atlantic and southern US.
Bitter rot appears on young fruit as small, circular brown lesions. Lesions expand rapidly and radially under wet and warm conditions. As they age, they turn darker brown and become sunken (A). When several lesions occur on a fruit they tend to coalesce and no longer appear circular. The spores of the fungus are creamy, white to pink, and tend to form in concentric circles within the lesion (B). The rotted flesh is often watery and appears V-shaped in cross section (C). The fruit eventually dries, mummifies, and may fall to the ground or remain hanging from the tree throughout the duration of the winter.