Fig. 1

Agaricus xanthodermus fruiting bodies. a Mushrooms (marked by arrows) underneath a Pseudotsuga menziesii tree on the 3rd of September 2015. b Drum-stick-like young mushrooms: the left one is grown to full size (the arrow points to the partial veil underneath the cap). c Mushroom opening and d fully opened mushroom with vestiges of the partial veil at the edge of the opened cap and a skirt-like annulus around the stipe (marked by arrows). e–l Diseased crippled young mushroom with split stipe and cap and an infested primordium partially covered by a fluffy foreign mycelium (marked by an arrow) on 1st of September 2015 at the day of detection (e), 1 day after (f, h; the arrow points to partial veil still attached to cap tissues), 2 days after (g, i; note the pinkish still healthy lamellae in i) and 3 days after (j), when the mushroom was harvested (k; note the now brown colour of the lamellae and the white foreign mycelium which covers the crippled stipe and grows onto the lamellae). After harvest, white mycelium was seen spread over the needle and cone litter layer, the decayed primordium and a cone from the Douglas fir underneath (l)