Occurrence Patterns and Control Methods of Jujube Witches' Broom
Jujube witches' broom is a devastating disease that should be prevented rather than cured. It is very prevalent in jujube-producing regions of China. Once a tree is infected, it rarely bears fruit the following year, and even if it does, the fruit loses its edible value; after 3~4 years the entire tree dies.
I. Causes of jujube witches' broom
The main cause of jujube witches' broom is the invasion of mycoplasma-like organisms. Mycoplasma-like organisms can be spread through grafting. Under natural conditions, natural root grafting between trees can also spread the disease, and some leafhoppers are also carriers of mycoplasma-like organisms.
II. Integrated control measures
1. Select and breed disease-resistant varieties; for example, Changhong jujube trees are more resistant to the disease than Yuanhong jujube.
2. Use disease-free mother trees, scions, and rootstocks, and cultivate disease-free seedlings; promptly and thoroughly remove diseased plants and diseased roots to prevent infection.
3. In jujube-producing areas, implement jujube-grain intercropping as much as possible to avoid contact between the roots of diseased and healthy trees, thereby blocking the spread of the disease.
4. Carry out proper ring-barking, which has the effect of blocking the movement of pathogens within the tree.
5. Before flowering and after petal fall, spray the canopy once each with 40% dimethoate emulsifiable concentrate at 1000 times dilution and 25% carbaryl wettable powder at 500 times dilution to kill the leafhoppers that transmit the disease.
6. Use a hand saw to make horizontal ring cuts around the trunk one full circle, reaching 1 millimeter into the xylem, at intervals of 30~50 cm, with 4 or 5 rings, which can block the downward transmission of the pathogen.
If a diseased tree has only a mild infection, after cutting off the witches' brooms, injecting antibiotics such as tetracycline and oxytetracycline into the xylem has a therapeutic effect, but it cannot eradicate the disease, and injection must be repeated when it recurs.