Grape root cancer is also called root head cancer. The pathogen is Agrobacterium tu_mefaciens (E.F. Smith et Townsend) Conn. It is called field bacterium or Agrobacterium tumefaciens and belongs to the genus Agrobacterium. The main species that infects grapes is type III. Grape root cancer is a bacterial disease that occurs on the roots, root necks and old vines of grapes.
Occurrence pattern
The pathogen overwinters in the soil along with the plant remains. When conditions are suitable, it invades the plant through various wounds such as cuts, mechanical wounds, insect wounds, hail wounds, and frostbite. Rainwater and irrigation water are the main vectors for the disease, and seedlings are the main way for the disease to spread over long distances.
After the bacteria invade, they stimulate surrounding cells to accelerate division and form tumors. The incubation period of the bacteria ranges from a few weeks to more than a year, and the temperature is suitable, there is a lot of rainfall, and the humidity is high, and the occurrence of cancer is also high. Heavy soil, high groundwater level, poor drainage and alkaline soil are more likely to cause severe disease. Root damage during seedling planting, root damage during field operations, and freeze damage can all encourage the invasion of pathogens. In particular, freeze damage is often an important cause of root cancer infection in grapes. There are differences in disease resistance among varieties. Rose fragrance, Kyoho, Red Globe and other varieties are highly susceptible to the disease, while varieties such as Longan and Kangtai are more resistant to disease. Rootstock varieties have great differences in their ability to resist root cancer. SO4, He'an No. 2, He'an No. 3, etc. are excellent disease-resistant rootstocks.
Characteristics and identification methods
A callus-like cancerous tumor forms in the affected part, which is slightly green and milky white in initial appearance and has a soft texture. As the tumor grows, it gradually turns dark brown, becomes hard in texture, and has a rough surface. Tumors vary in size, and some clusters of dozens of tumors can form large tumors. The surface of mature tumors is cracked and easy to rot and fall off in rainy and humid weather, and has a fishy smell. Due to the destruction of the cortex and conductive tissue of the affected plants, the tree vigor is weak, the plant growth is poor, the leaves are small and yellow, the fruit ears are small and scattered, the fruit grains are not neat, and the maturity is inconsistent. Diseased plants have few branches and weak growth. In severe cases, the plants dry up and die.
Use pesticides
(1) Bacteria and toxin removal
Dosage: 5%AS
Control period: After discovering the diseased spot, apply it twice on the cured diseased spot (with an interval of 7 to 10 days).
Instructions: Use 300 grams of 5% AS, mix with 15 kilograms of water, dilute it to a 50-fold solution, stir evenly, and apply it on the lesions after curettage; use 75 grams of 5% AS, mix it with 15 kilograms of water, dilute it to a 200-fold solution, and stir Spray the tree trunks evenly.
Precautions: Do not mix with other pesticides. Crystallization is easy to occur at low temperatures. Use warm water in a bottle to dissolve it without affecting the efficacy.
(2) Thiram
Dosage: 50% WP
Control period: Apply to the lesions when they are found, and apply it twice on the lesions after scraping (with an interval of 7 to 10 days).
Instructions: Use 300 grams of 50% WP, mix it with 15 kilograms of water, dilute it to a 50-fold solution, and apply it on the lesions after scaling.
Precautions: Do not mix with copper, mercury and alkaline pesticides or use them in close succession; seeds mixed with pesticides have residual poison and cannot be eaten anymore. It is irritating to the skin and mucous membranes, so be careful when spraying; store in a cool, dry place to avoid decomposition.
