The pathogen of orchid rust disease is Uredo apidendrum

The spermogonia (O) and aecia (I) of this fungus have not been observed; the uredinia (II) are borne on both surfaces of the upper or lower part of the leaf, appearing as brown, blister-like raised spots with pale red edges, which eventually cause the epidermis to rupture; the telia (III) have not been observed. (1) Damage: Uredo epidendrum isorchida relatively uncommon rust fungus, and theorchidhosts that have been found mainly include: Oncidium cavendishianum, Diacrium, Bilamellatum, Epidendrum nocturnum, E. venosum, Ionopsis sp., Laelia sp., Rodriguezia sp., and Trigonidium semamix. (2) Symptoms: This rust disease occurs only on leaves; the typical symptom is the production of raised brown spore masses, usually with pale red edges. Symptoms first appear on the underside of the leaf, and as the disease develops, spore masses form on both surfaces of the leaf; when the spore masses mature, their color changes from brown to purplish black. (3) Control methods: Destroy all diseased plants, and apply a protective fungicide to all susceptible orchid plants, such as ferbam, at a dilution of 800 times, treating once every 7 days. Liu Zhongjian