Prevention and treatment of lettuce giant vein disease
Damage symptoms
Lettuce macrophage is a common disease in open field cultivation. It was initially clear vein-like, and the veins and tissues of the veins became uneven and splayy or mottled. The veins were thick, erect, and shrunk; the veins of the lettuce were white and green. Obvious bright green to pale veins, translucent part of the veins, extending to the base of the leaf. The "vein belt" is a special symptom of the disease, which is called giant vein disease or large veins. In the latter stage, the diseased leaf is curled and shrunk. The diseased plant is short and the growth is hindered. The normal leaf ball cannot be formed and the value of the product is lost.
Pathogenic characteristics
Lettuce big vein virus referred to as LBVV lettuce giant vein virus. It has been reported that the RNA of this virus was recently found and identified as the original virus. The LBVV host range is narrow, limited to several Asteraceae plants. The lethal temperature is 65°C for 30 minutes and the dilution limit is 200000 times. In addition, it is thought that MLO can also cause the giant vein disease caused by mycoplasma.
Transmission routes and conditions
The disease is mainly transmitted by the zoospores of the oil in the soil. After invading the roots, it releases the virus. After 4-5 weeks of onset, the virus transmitted by the bacteria can be obtained from peas, spinach, leeks, rhubarb and car money. Isolated on the plant. The oil bacterium can survive in the soil for 10 years. When the seedlings are raised, if the substrate is poisonous, it will be obvious after 4 weeks of infection, and it is generally not easy to find. However, if the diseased strain is planted in a nutrient film system, the oil strain will produce a large number of zoospore and spread quickly. In addition, sap inoculation into the root can also be transmitted. The temperature is 14°C and the symptoms are severe. At 24°C, it is latent and the continuous crops are prone to develop.
Control methods
(1) The disease is prone to occur in plots where lettuce is often planted, and production should be carried out for 2-3 years. (2) Seed bed disinfection Before seeding, the seedbed is disinfected with 50% thiophanate-methyl WP, 8-9 g per m2, mixed well with sieved alfalfa, spread on the bed, and then nursed. Certain prevention and control effects. (3) The use of soilless culture, can be added in the nutrient solution of 0.1% 50% carbendazim WP, but also effective in preventing and treating this disease. (4) The shade net can be used in the field to reduce the temperature in the field and avoid excessive temperature.
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