oidium

From New Latin ōidium, equivalent to Ancient Greek ᾠόν (ōión, “egg”) +‎ -idium.

oidium (plural oidia)

1. A fragile spore produced by some fungi.
   • 2003 August, Competition Science Vision, page 802:

     • Oidia are hyaline, small and thin-walled unicellular sections or fragments of the mycelium.
     • Oidia may be uni- or binucleate as whether they are produced by the breaking up of the primary or secondary mycelium.

   • 2004, P.D. Sharma, The Fungi, page 241:

     However, in some forms mainly some Hymenomycetes it occurs by the formation of oidia. The oidia are of two main types.

   • 2006, A. V. S. S. Sambamurty, A Textbook of Plant Pathology, page 239:

     Later the pods become covered completely with white powdery mass composed of mycelium, oidiophores and oidia of the fungus.

2. The fungus Erysiphe necator (= Uncinula necator), which produces powdery mildew in grapes.

• conidium

Borrowed from French oïdium.

oidium n (uncountable)

1. powdery mildew