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Fungi/Fungi-Like Organisms

The largest group of plant pathogens are the fungi and fungi-like organisms. The fungi-like organisms were originally classified as fungi, but have subsequently been broken out into their own group, and we usually refer to these, kind of informally, as water molds. Again, this is the largest group of plant pathogens. There are more than roughly 8,000 different organisms in this particular group that can cause disease. And, keep in mind that there are lots of additional fungi that are out in the environment that do not cause plant diseases, but there’s a large group of the fungi and fungi-like organisms that do.

What I like about the fungi is that they are relatively large compared to the other types of disease-causing organisms that we’re going to be discussing today, and they can oftentimes be seen with the naked eye. If you’ve ever been in the grocery store and walked by those mushrooms in the vegetable section, those are fungi, and so, as you can tell, again, those are relatively large. A lot of the ones though that I tend to look at when I’m looking at disease-causing organisms tend to be microscopic, and I do need to use a microscope to see at least some of the structures that I need to see in order to identify them.

Fungi can grow in a couple of different ways. Usually in their day-to-day growth, we call this vegetative growth, and they do this through production typically of structures called hyphae (singular is hypha without the “e”), and these are basically long, threadlike structures that form the main body of the fungus. Typically, these structures are multicellular, so you’ll actually be able to see many cells within a given thread, and these can be quite extensive and grow over a large area.