Fungus growing in the asphalt below my oak trees

Asked November 3, 2015, 2:25 AM EST

I have some kind of opportunistic fungus (is that redundant?) that's growing in a small pitted area of my asphalt driveway. It is spreading from below the observable surface and I'm uncertain how to destroy it. I believe there is some kind of mushroom that grows on the roots of oaks and they are dependent on each other for nutrients. Perhaps that's what this is? I don't want to harm my oaks, but this is compromising the asphalt and the area keeps getting bigger. I have used an organic moss killer concentrate that stops it where it makes contact, but then it keeps spreading out under the surface and coming up. Help, please!!

Benton County Oregon fungi

1 Response

Unfortunately, I can not ascertain the identification of this fungus without better pictures and/or microscopic examination. However, you are correct, there is a fungus that is a pathogen to oak roots -- it's often referred to as the "shoestring root rot" (Armillaria mellea). If it is Armillaria, there are currently no registered controls for the fungus. There are a number of fungi that have been known to grow up through asphalt including Coprinus comatus and several Agaricus spp. However, I can't find any recommendations for controlling these aside from letting them run out of nutrients or ripping up the asphalt, removing the top foot of soil, and replacing with gravel before repouring asphalt.

http://pnwhandbooks.org/plantdisease/oak-quercus-spp-armillaria-root-rot

http://www.nytimes.com/1997/09/25/garden/garden-q-a.html

http://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/Armillaria.aspx