Sustainable Mycology: Alternaria spp.

I am beginning a series on the most common fungi identified during the course of indoor air fungal investigations.

The organism Alternaria spp. is a common leaf decay fungi with higher outdoor numbers in the late summer through fall. The outdoor numbers drop dramatically after the first snow fall and typically remain low throughout the winter.

The organism is easily identified on a spore trap sampler such as an Air-o-Cell. It will also grow well on PDA (Potato Dextrose Agar), MEA (Malt Extract Agar) and in most cases DG-18 (Dichloran Glycerol Agar) with incubation at 25 degrees C.

It is often a cause of seasonal allergies. Because of its relatively large size it will deposit in the upper respiratory tract. I have found it growing on window ledges in buildings and on sheet rock walls. The spores are commonly deposited on dusty surfaces and floors. The surface deposition levels are often greater in homes and offices with open windows.