What causes jujube witches' broom disease?

Jujube witches' broom is a devastating disease of jujube trees. After a jujube tree is infected, it shows the following abnormal phenomena: 1. Floral organs revert to a primitive state, the flower stalk lengthens to 3-6 times that of a normal flower, and the sepals, petals, stamens and pistils grow abnormally, becoming light green small leaves. On diseased trees with stronger vigor, thin, short, small branches may also sprout from the leaf axils of the small leaves, forming clusters of branches. 2. The main and secondary buds of the developing branches and the fruiting mother branches sprout and grow multiple times a year, continuously producing thin, small, yellow-green branches and leaves that form dense clusters of branches, which do not easily fall off in winter. 3. On the branches and trunk of the whole tree, the originally dormant latent buds sprout in large numbers, producing yellow-green, thin, small clusters of branches. 4. Sometimes small-leaf, clustered, branch-like root suckers sprout from the ground beneath the tree.

The occurrence of jujube witches' broom generally first shows symptoms on some branches and root suckers, and then gradually spreads to the whole tree. After young trees are infected, they generally die within 1-2 years, while large trees infected with the disease generally gradually die over 3-6 years.

The pathogen of jujube witches' broom is a phytoplasma (MLO), a microorganism between viruses and bacteria. Current research has established: 1. Grafting can transmit the disease. After young trees are grafted with diseased branches, the incubation period is as short as 25-31 days and as long as 372-382 days. 2. Pollen, seeds, sap of diseased leaves and soil do not transmit the disease. 3. Insects such as the Chinese holarctic leafhopper (Hishimonus sellatus) and the concave-margined holarctic leafhopper are the main vectors that spread the pathogen.