Alternaria

Alternaria is a fungal blight where leaves develop brown to black spots which enlarge and develop concentric rings like a target. Lower leaves are usually hit first. Spores are carried by air currents.

Alternaria is a genus of ascomycete fungi. Alternaria species are known as major plant pathogens. They are also common allergens in humans, growing indoors and causing hay fever or hypersensitivity reactions that sometimes lead to asthma. They readily cause opportunistic infections in immunocompromised people such as AIDS patients.

There are 44 definite, well-known species, but there may be hundreds more. They are ubiquitous in the environment and are a natural part of fungal flora most everywhere. They are normal agents of decay and decomposition. The spores are airborne and found in the soil and water, as well as indoors and on objects. The club-shaped spores are single or form long chains. They can grow thick colonies which are usually black or gray.

There are fungicides that can control alternaria. Read the labels for proper application and do contact a local Master Gardener or Country Extension Agent for advice.