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SYMPTOMS OF FUNGAL DISEASES

We are able to identify powdery mildew and rusts, in part, because the pathogens produce distinctive fungal structures (generically called SIGNS) that we can easily identify. Most diseases will not be this cooperative.

For most fungal diseases, we must rely on disease SYMPTOMS to help us to determine the cause of the disease. Symptoms are simply abnormalities in a plant that arise during disease development. Most of the time symptoms will NOT definitively tell us the exact disease problem, but often symptoms can give us a sense of whether a disease is caused by a fungus or some other pathogen.

WHAT KINDS OF SYMPTOMS ARE CAUSED BY FUNGAL PATHOGENS?

SPOTS are a common symptom of fungal pathogens. A spot is simply a roughly circular NECROTIC (dead) area, typically found on a leaf. Larger, more irregularly shaped spots are sometimes referred to as LESIONS. Sometimes fungal spots or lesions have yellow haloes.

This slide shows black spot of elm caused by the fungus Gnomonia ulmea.