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Mushroom Cultivation: Face-off with Fungus Gnats

So my harvests have been ruined! Oh no, oh no, oh no no no no no.

The culprit is the Fungus Gnat that has been laying eggs on my mushroom blocks and whose squggly, tiny, white maggot pupa then eat my Oysters from the inside out. To those of you who know yiddish vernacular: OY VEY!


The Culprit: Fungus Gnat of the Sciaroidea family.

So as soon as I started seeing these pupa of the fungus gnat, I started to strategize my defense. I learned about the attacker, it's lifecycle, it's food sources and I learned that fungus gnats really piss of people with house plants. I could move my grow indoors or protect the blocks with protective netting, but I want to do this as low tech and inexpensive as possible. I also had a feeling that nature had a solution to my dilemma. Also, I have to say that as soon as I saw fungus gnats swarming the ONLY Oyster mushroom that I found on a recent hike, I was put at ease that my cultivated outdoor mushrooms weren't the only ones that are dealing with this issue.


No, turtles don't eat fungus gnats... but there are other things that do! So, the easiest method and the method that I chose was to use BTI (Bacillus Thuringiensis Israelensis), commonly called Mosquito Dunks. This bacteria produce a toxin in the spore producing stage that is toxic to mosquito larvae and fungus gnat larvae. The toxin is ingested by the larvae and who then die within a number of hours. In threory, this is great. However with any microbiome, it takes time to get established as a community and there are a number of road blocks along the way. If the BTI works as intended, it takes only 24 hours for the larvae to start dying after consuming the toxin.


There are also nematodes and mites that can be released into the environment that serve the same function of predating the fungus gnat larvae. Since I am working on creating a microbiome that supports my mushroom blocks. I am hoping that the BTI treatment will work, but there are other methods that I am incorporating in order to reduce the fungus gnat invader ever more. I have placed yellow sticky traps in the surrounding area around my blocks. It is true that most yellow sticky paper is used to indicate where to treat, however, together with the BTI, I am hoping that I will be able to reduce the fungus gnat population in my ecosystem through natural predation and mechanical methods.


Cultivation and foraging as a combination adds an element of pride and an unknown to your diet. There are insects whose main diet is fungi and decaying organic matter, this is exactly what we are searching for in our foraging outings and in cultivation. There are times when the mushroom finds us and there are times when we find the mushroom after the mushroom had found some lucky insect. I ultimately believe in balance in the ecosystem, and I know that if I keep it up, the system will balance itself out. So maybe I am getting too stressed about some fungus gnats and a few thrown away mushrooms. In the end, the forest knows and endless abundance abounds.


For questions, comments, feedback, insults: adamganson@gmail.com

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