Researchers treated a medicinal mushroom (Cordyceps militaris) with antifungal drugs at non-lethal doses and found that this stress affected the mushroom’s internal clock and fruiting body development. Interestingly, while most fungicides caused the fruiting bodies to degenerate, one drug (5-fluorocytosine) surprisingly rejuvenated degenerated strains. The effects persisted even after removing the drugs, suggesting fungicides cause lasting changes to the mushroom’s circadian rhythm.