Extension | Black Rot Disease in Apples

Mirjana Bulatovic-Danilovich, WVU Extension Specialist, Consumer Horticulture – Agriculture & Natural Resources Black rot disease, caused by the fungus Botryosphaeria obtusa (Schwein), is concerning to homeowners with apple trees as part of their landscapes. All apple cultivars are susceptible to it, but it appears that McIntosh, Cortland, Empire and Northern Spy varieties are the preferred hosts. It seems that black rot is becoming more of a problem than usual. Normally, protectant apple scab programs would keep black rot in check. But, since incorporating other materials (like sterol inhibitors) that have no effect on these fungi, symptoms were more readily observed in the orchards throughout the state. Disease symptomsDiseased limbs show symptoms that resemble fire blight. They appear as reddish-brown sunken areas with rough, cracked bark. The old cankers are dry and appear blistered, peeling and revealing black pimple-like, spore-carrying structures (Figure 1). Leaf lesions start a...