Detailed Explanation of Orchid Rust and Its Pathogen Uredo negropunctata

(Synonym: Uredo Cyrtopodii) Uredinia (n) are found on the underside of the leaves, forming irregular light black patches, containing cinnamon-brown urediniospores. Pycnia (O), aecia (I) and telia (III) are unknown. (1) Damage: Reported host plants of this fungus include: Bletia purpurea, Epidendrum tampense, Bletia patula, Cyrtopodium punctatum and Stanhopea sp., etc. The pathogen has been found in the United States, Brazil, Argentina and other countries. (2) Symptoms: The symptoms caused by this fungus on Epidendrum tampense are similar to those caused by Sphenospora kevorkianii on this host. Diseased plants form typical irregular orange-yellow and black spore masses on both sides of the leaves. On Stanhopea sp., the spore masses are light brown to dark brown, raised, and often appear on the underside of the leaves. (3) Control methods: Remove and burn all diseased leaves, spray with ferbam at 800 times dilution, add a small amount of spreader to the solution, and treat once every 7 days. Liu Zhongjian