ETIOLOGY OF APPLE SOOTY BLOTCH DISEASE IN NORTH-CAROLINA

Sooty blotch disease of apples (Malus x domestica), previously attribu ted to the fungus Gloeodes pomigena, was shown to be a disease complex caused by fungi previously considered mycelial types of G. pomigena. Peltaster fructicola and Geastrumia polystigmatis were associated with the ramose mycelial type. A fungus similar to P. fructicola, but with smaller pycnothyria and conidia, was associated with the punctate myc elial type. The diffuse fuliginous mycelial type was caused by Leptodo ntium elatius. Fungi that fit the classical morphological description of G. pomigena were not observed. Pycnothyria of P. fructicola develop ed on overwintered colonies on blackberries, and conidia were a source for primary infection during the entire growing season. Secondary spr ead was through conidia produced in colonies on fruit. L. elatius was observed infrequently producing conidia on fruit during periods of ext ended high moisture. Histological examination did not reveal penetrati on of the cuticle of apple fruit for any of the fungi of the apple soo ty blotch complex.