Dog Poop Fungi

By Mike Davison, 2021

Don Poop Fungi – Pisolithus tinctorius and Pisolithus microcarpus

Pisolithus is a very common fungus in forest settings and it can be found in our yards and green belts here in Serrano Park. Having this fungus here is actually great news as this fungus plays an important roll in tree health. It is beneficial to many species of trees but especially pines and eucalypts. Commercial forestry services use these fungi to inoculate seedlings. I am not sure which species we have here as they look the same to me. I have found it along embankments and in my yard near pines, eucalyptus, and shrubs.

P. tinctorius and P. microcarpus are fungi that survive and thrive by forming a symbiotic relationship with plants and especially trees. The part you see above ground, is the fruit of the fungus that is full of spoors. Under ground there exists a vast network of mycelia that binds and penetrates into roots as well as seeking out water and minerals in the soil. This is called ectomycorrhizal symbiosis. It forms a barter system with the trees where it trades filtered water and minerals for sugars and fats resulting in enhancing the tree’s root system to reach further and to find rare minerals and nutrients that the tree needs. It is excellent in filtering out toxins for the tree and greatly enhances the root’s ability to find what it needs. This network will even help pass the sugars and fats from a tree in the sun to a tree in need of food in the shade. For its services, it uses some of the tree’s sugars and fats, slowing the tree’s growth.

Slowing the growth of the tree is a good thing. Trees are healthier, stronger, grow larger, and live longer, when they grow slow. (See “Urban Tree Mortality Grow Fast, Die Young: The life cycle of an urban tree”) The nutrients they get from the fungi are free of toxins and the mycorrhizal network is far better at finding trace minerals the tree may need. Trees and mycorrhizal fungi have evolved together and depend on each other.

What this all means is great news. Parts of our urban forest are behaving like a real forest with a symbiotic ecosystem forming that stabilizes the health of all the species involved. So, keep an eye out for these wonderful fungi and don’t automatically blame what you see on someone’s dog.

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