Apple Alert: Marssonina Leaf Blotch Confirmed in Western NC

— Written By

Sara Villani and Rachel Kreis | 9/24/2018

Last week, Marssonina leaf blotch, caused by the fungal pathogen Marssonina coronaria was confirmed in several ‘Rome Beauty’ trees in Western NC. While this disease was sporadically observed in the Hudson Valley region of NY in 2017, to my knowledge this is the first time it has been confirmed in NC. So far we have only observed the disease on ‘Rome Beauty’ trees in the region. However, from a quick read through the literature, it appears as though nearly all cultivars are susceptible to the disease including ‘Fuji,’ ‘Mutsu,’ ‘Golden Delicious,’ and ‘Winesap.’

Image of Marssonina leaf blotch

Symptoms: Symptoms of Marssonina leaf blotch appear strikingly similar to Glomerella leaf spot (GLS). Infected mature leaves have grayish-brown lesions often with purple borders. While lesions associated with GLS may be concentric, we have not observed this characteristic with Marssonina leaf blotch. Like GLS, severely infected leaves become chlorotic (yellow) and defoliate prematurely. Although these more severe symptoms can occur during early summer, we have only observed these advanced stages of this disease over the past few weeks (since early September). Acervuli (small, black fungal structures that contain conidia) have been present on several lesions that we have examined. Although fruit can become infected it is uncommon and has not been observed in Western NC.

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