Below are several questions that I asked of UVM Plant Biologist Terry Delaney in regards to how to deal with toxic mushrooms in our yard as a follow up discussion to what happened to our dog. I thought it would be helpful to share this information since these postings have made their way around some broad audiences. Terry’s responses are in italics below.
Q: During how much of the year do these most poisonous mushrooms prevail? i.e. do they “hibernate” in the winter and how early in the spring do they “bloom” and how long into the fall do they last?
A: Most mushrooms are most abundant toward the end of summer, up until the fall frost. There are some that are spring fruiters (such as the edible Morels), but they are in the minority. Having said that, you could find some autumn fruiters in June on occasion. The mycelium is the netlike organism that lives in the substrate (soil, or wood, for example). It is present year-round, but only sends up fruits (mushrooms) when conditions are favorable, such as mild temperatures, good moisture, and proper time of year. In the dead of winter, things are pretty much shut down, much like hibernation. The deadly Amanitas generally follow the late summer-fall fruiting pattern, though earlier fruiting can occur. Though Galerina autumnalis is named that, is also can be found earlier in the year than only in autumn. So, the best thing, is to learn to recognize the relatively few very dangerous mushrooms (Amanitas and Galerina autumnalis).
Q: Where does their poison come from? I’m assuming there’s some kind of chemical process that occurs that creates the toxins? Is it coming from the decay in the soil and on dead logs?
A: The most deadly poison in these mushrooms is alpha-amanitin, which is found throughout the mushroom body. The toxin is actually a protein that is made as an inactive, larger precursor protein that is clipped down to an 8-amino acid peptide that is formed into a ring (cyclized), and slightly modified to for a cyclic peptide poison. These processes occur entirely within the mushroom body, presumably in all of the cell types of the mushroom. There are also several closely relate amatoxins, that are made in the same way but are slightly different in structure.
Q: How long do they take to grow? i.e. if you were to eradicate a yard of as many of these as you could find, how long before you should make another round? a few days, a week or more or less often?
A: I don’t know how long a new colony (mycelium) takes to form mushrooms. Some cultivated mushrooms can do this in just several months to a few years. I suspect it takes at least several years for Amanitas to establish themselves from a spore, and make new fruits. In terms of an existing area, if a type of mushroom has been seen there before (especially the region where you found the destroying angels), I would suggest regularly scouting the area for the telltale white mushrooms, and if seen remove them with the volva (as it too contains amatoxins). You’d never eradicate the mycelium through this process, in my opinion, but it is the mushrooms that are hazardous. With a child, I’d supervise them carefully around mushrooms and not let them near the really bad ones. With a very mouthy pet, I’d do likewise.
Q: Is it okay to discard them in composters that will eventually be used in garden soil for vegetables that we’d eventually consume?
A: Even deadly mushrooms would compost well. The toxins, though stable in the lab, would not be taken up in the plants and would more likely be broken down in the composting process. If you are still concerned, you could throw the few you have in a toilet or a fire. I wouldn’t worry about it, provided pets/kids don’t raid the compost.
I agree that eradicating the woods of mushrooms is not possible, nor is it desirable. The vast majority are beneficial as decayers or symbionts with plants. I would police the area where pets or children explore, and remove Amanita’s and Galerina, if they might consume them. Though it is no consolation to you given your sad ordeal with Bee, the occurrences of pet poisonings are quite low, given the number of animals and mushrooms out there. I’d be happy at some point to send you some pictures of Galerinas, so you can recognize them.