Orchid fly fecal spot disease

This disease causes little harm to orchids and is generally overlooked. It does not harm many species, only found in Catalan, Dendrobium and Vanda. Generally speaking, orchids growing in shade are susceptible to disease. When the disease occurs, pin-sized black patches similar in size and color to fly droppings are seen on both sides of the leaf, consisting of closely intertwined mycelium of the disease, both on the front and back of the leaf, but more commonly on the back of the leaf. These small spots often gather together and present multiple black heaps on the leaves. In severe cases, multiple black heaps can cover the entire leaf. The black heaps are not independent of each other, but are connected by very fine strands. The fungus does not penetrate leaves and can be wiped off with a gentle rub.

Microthyriella rubi was identified as the pathogen of the disease, and its control was not a big problem. It could be gently wiped off with soft cloth dipped in water, and it could also be controlled with conventional fungicides for controlling other serious diseases. (Liu Zhongjian)