Orchid rust: Sphenospora kevorkianii

The spermogonial (O) and aecial (I) stages are unknown; the uredinia (11) are small, raising the epidermis, cinnamon-brown, with the epidermis cracking open to release yellow-brown to yellowish-brown spores. The telia (III) form beneath the epidermis of the lower leaves, in concentric circular groups, pulvinate, wax-yellow-brown. (1) Damage: This disease was discovered and described by Cummins in 1945 on Cycnoches ventricosum var. chlorochilon P. H. Allen in Venezuela. Other hosts include: Bletia sp., Catasetum sp., Epidendrum nocturnum and Mormodes sp. The disease affects few host species and cannot be considered serious. (2) Symptoms: On Cycnoches ventricosum var. chlorochilon and Epidendrum nocturnum, pinhead-sized cinnamon-colored raised lesions first form beneath the leaf epidermis; the lesions then age, break through the leaf epidermis and produce cinnamon-brown to golden-brown powdery spore masses. (3) Control methods: Remove and burn all diseased plants; spray affected plants with ferbam at a dilution of 800 times, applying the chemical once every 30 days. (Liu Zhongjian)