Orchid arbuscular disease

Orchid witches' broom disease has not been reported at home and abroad. In 1994, it was first found in the general field of Wutong Mountain nursery in Shenzhen City. The initial symptom of the disease is leaf shrinkage, which mostly starts from the top of the leaf, hardens and becomes brittle, and the leaf shrinks. There are many small protuberances in the middle and upper part of the leaf, which have a rough feeling. Later, when sprouting, the tillering buds tend to be larger at first, and then a number of small buds appear around the big bud. These buds do not grow roots and do not form ramets. Black spots often appear on the top leaves of tillering buds, and the plants are often dwarfed. Most of the shorter varieties are susceptible to the disease. The pathogen may be plasmodium MLO, but further study is needed. (Liu Zhongjian)