Powdery Mildews

I've probably been seeing powdery mildew fungi for my whole life. From time to time I notice them growing on wild bergamot, willow, and dandelion to name a few. Most of the time I just walk on by without even seeing them. Recently I've started to actively pay attention and learn about this group. It is amazing how abundant and diverse they are. Most would think that these infections are not aesthetically pleasing, but I think they are quite fascinating, especially as I learn more of their ecology.

Powdery mildews like many fungi thrive in cool, moist areas. Exploring the Devil Track River was the perfect place to find many different species. Unsurprisingly many of the plants were also infected with rust fungi.

Erysiphe adunca on balsam poplar (with the rust species Melampsora medusae) 

Golovinomyces asterum var. solidaginis on goldenrod (with the rust species Coleosporium solidaginis)

Golovinomyces sordidus on greater plaintain

Erysiphe pisi on bird's foot trefoil 

Golovinomyces biocellatus on lycopus 

Golovinomyces hieraciorum on hawkweed

Golovinomyces bolayi on harebell (with the rust species Coleosporium campanulae)

Podosphaera erigerontis-canadensis on dandelion

Golovinomyces asterum var. asterum on big leaved aster

Erysiphe capreae on willow

It is easy to look at these plant diseases as only a negative, as they damage the health of their host plant. However, they seem to have little effect unless there is a very large outbreak. Furthermore many of these are on non-native species so inevitably benefit the overall health of the ecosystem. On native species they surely play a regulatory role, preventing a single species from outcompeting everything else by increasing the severity of the outbreak when the host population increases in density. They also play a role in the cycling of nutrients, helping kill and breakdown living things so that new life can begin again. Today I found at least ten species without looking very hard or for very long, how many might be in the area?



















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