Wood-rotting fungi are a rich source of antiviral compounds, many of which have long been used as medicines, particularly in China. […] Adding a one percent extract of amadou (or Fomes) and reishi (Ganoderma) to bees’ sugar water reduced deformed wing virus eighty-fold.
Source: The Fungal Evangelist Who Would Save the Bees – Issue 90: Something Green – Nautilus