In this publication, we describe apple blotch disease, also known as Marssonina leaf blotch, an emerging apple disease in the Eastern United States. This disease leads to severe apple tree crown defoliation that indirectly affects the apple fruit size, color, yield and twig development. The causal gent of this disease is a fungus Diplocarpon coronariae (also known as Marssonina coronaria).

Fungal species in the Colletotrichum genus are the causal agents of bitter rot on apples. In Virginia, six Colletotrichum species cause apple bitter rot: C. fructicola, C. chrysophilum, C. siamense and C. theobromicola from CGSC and C. fioriniae and C. nymphaeae from CASC. Over the past two decades, bitter rot infections have been increasing in the Mid-Atlantic region, where these pathogens are becoming more prevalent due to increasingly warm and wet weather conditions that favor Colletotrichum growth. The region produces approximately $500 million worth of a worth of apples every year. Losses to bitter range from 14% to 100% in commercial apple orchards. This publication describes causal pathogens, their biology and management approaches and has practical and scientific significance.