1. Symptoms Populus canker disease mainly occurs on the trunk and forms a nearly round, ulcerous spot with a diameter of about 1 cm. Twig victims often die. There are two types of lesion formation process: 1 Blister type: A round blisters of about 1 cm in size are formed on the surface of the cortex, and the sap is filled with sap, and brown sap-floating sap flows out. After dehydration and dehydration, the blister forms a dark brownish brown spot with a slight depression. Blister lesions appear only on the trunks of saplings and branches of the light skin species. 2 Fading spot type: First, a water-soaked round spot of several millimeters in size appears on the bark, slightly raised, and the hand pressure has a soft feeling, and then it becomes a dark brownish round spot that shrinks into small depressions. 2. The onset of the disease The pathogens mainly overwinter in the diseased tissue with mycelium (also immature fruiting bodies). The germs are mainly transmitted by wind and rain. The transport of propagation materials such as seedlings and scions can carry long-distance transmission. The pathogen has latent infection. The occurrence of this disease is closely related to the water content of the bark. The pathogenic bacteria are weak parasites. All kinds of reasons that can weaken the trees are the cause of the disease. For example, seedling transplantation, spring drought, cold spring, wind and sand, extensive management, and saline-alkali soil are all pathogenic. Different poplar varieties have significant differences in resistance to ulcer disease. 3. Control measures 1 Based on the nursery, cultivate healthy seedlings, strengthen quarantine, and ensure good seedling quality. Disable serious planting of seedlings after afforestation or planting after cutting. 2 Breeding disease-resistant tree species, appropriate tree selection, selection of tree species adapted to local site conditions and climatic conditions, and exerting their own resistance to diseases. (3) Minimize water loss in seedlings during tree planting, and take various measures to increase the water content of the trees. 4 chemical control. In the period from April to May or mid-August before the onset of illness, spray 10 times the food lye or 50% dexamethasone 100 times or 40% methasor 100 times or 50% tetr 100 times and dilute tar. And so on, all have the effect of inhibiting diseases.
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