Fungus gnats

In October, this Polypore had thin white treads attached to it. In November, I returned and saw small holes bored into the Polypore (picture 5). When I took it off the trunk, I noticed a small white worm with a tan head (picture 3). Fungus gnats (Sciarids) (Lycoriella spp.) and phorids (Megaselia spp.)

Adults are small (1/8 inch long), fragile grayish to black flies with long, slender legs and thread-like antennae. Their wings are clear or smoky-colored with no pattern and few distinct veins. Larvae are clear to creamy-white and can grow to about 1/4 inch long. They have shiny black head capsules.
They are attracted to the mushroom crop and their larvae feed directly on mycelium, swarm over the mushroom, and tunnel into the developing or developed mushroom. Tissues that have been physically damaged by flies often become colonized by bacteria which cause soft rot, thereby accentuating the problem. Even a small crack will serve as an entry for the flies.