Tiny spots with circular yellow rings on dendrobium leaves (pictures included)

[Selmo]

Anthracnose not real common but is common to these types of dendrobium hybrids. Usually the leaves will yellow, have circles or rings like that and fall off. Most often it will not cause harm to the plant, other than unsightly leaves and bare canes.
Happens in warm humid conditions with poor air movement. Good cultural practices, good air movement and limiting leaf wetness time should keep it controlled. No need to spray chemicals for this.