Douglas Harper's Etymology Dictionary
myco-
before vowels myc-, word-forming element meaning "mushroom, fungus," formed irregularly from Greek mykes "fungus, mushroom, anything shaped like a mushroom," from PIE root *meug- "slimy, slippery" (see mucus). The correct form is myceto- (mycet-).
Wiktionary
myco-
pre. (context biology English) fungus