The more I learn about the natural relationships just in our yard, the more awestruck I am at the complexity and balance within nature....
This summer I've been seeing these big, ugly mushrooms in the grass of our back (court)yard area. They range up to about 8" in diameter, are yellowish-brown on top, and their caps become wavy as they mature, sometimes revealing their yellow undersides in a rather flirtatious way. These mushrooms have very short stems that are generally hidden and often off center. Evidently they are extroverts - in that they usually occur in small clusters.
Yesterday while I was clearing out a new area for a bed, I ran into a large group of them hidden in the grass and weeds that had grown up. There was no way to do the weeding I wanted to do without touching the mushrooms quite often and I began to wonder if I needed to be cautious about handling them. That led, rather naturally, to feeling the urge to identify them.
The first book I checked left me feeling inadequate, so I moved on to A Guide to Kansas Mushrooms. Success! What I had were ash tree boletes, aka Boletinellus merulioides. Not only were these mushrooms not poisonous, they are actually supposed to be edible (with the small caveat that they taste rather like dirt). They are found under ash trees, as their name suggests. Coincidentally, the two trees shading our courtyard are green ash. It all seemed very straightforward.
Being somewhat compulsive about these things, though, I wanted to find out a little bit more about their biology, so I continued my search on the web. That's when I got a few hints that things might be a touch more complicated than they had looked initially.
The first site I visited, Mushroomexpert.com, talked about ash tree boletes not actually being mycorrhizal with ash trees, as I had assumed, but symbiotic with ash tree aphids. Hunh?
Another site said they were "associated with the aphid farming of ants around ash trees."
Finally I found a site by Oregon State University that named the aphid in question, Prociphilus fraxinifolii. Other sites gave me common names for the aphids involved, woolly ash aphid or ash leafcurl aphid. (Multiple common names for the same species of plant or animal is why scientific names are so wonderful.)
While I am not sure that I have the entire life cycle and interrelationship completely figured out, here is what I can piece together so far.... The woolly ash aphid (aka ash leafcurl aphid) seems to feed on the ash tree in two places: in the spring it feeds on newly emerging leaves, creating a deformed, curled effect in them that is especially problematic in young nursery plants; the rest of the year it seems to feed on the roots. The aphids can overwinter either as eggs in the tree bark, or as immatures below ground on the roots. When feeding on the roots, the aphids are surrounded by sclerotial tissue from the ash tree bolete, providing the mushroom with "honeydew" sugars as food in return for shelter and probably protection from predators from the mushroom. Again and again I read that ash tree boletes do not have a mycorrhizal relationship with the ash trees themselves.
So I am left with questions: Have I missed a major wrinkle in this complex relationship? Can the ash tree bolete survive without the aphids? Does the fact that I have numerous ash tree bolete mushrooms this year mean that we will have a bad outbreak of woolly ash aphids next year? (I see no signs of curly leaves on my trees this year, although there could be a few curly leaves hidden within the canopy.) Should I remove and destroy the ash tree boletes to interrupt the life cycle of the aphids? Do I trust my identification skills enough that I'm willing to cook up some ash tree boletes and taste test them?
Time will answer some of these questions. If anyone else has an answer or two for me, I'd be happy to hear them. Meanwhile, I'll just wait and watch...and probably NOT try taste testing. Somehow, the idea of a dirt-flavored mushroom isn't quite appetizing enough to risk much for!