1. Symptoms and characteristics The disease damages the branches of poplars, and the incidence of saplings that have just been transplanted is the most important. There are two types of lesions. 1 Blister type, the most common symptom, mainly with watery lesions, round or oval shape, diameter of about 1 cm, the edge is not obvious, brown spots of hand-pressure lesions out of the liquid, the latter spot subsidence, grayish brown There are cracks in the center. 2 In the dead spot type, several millimeters of water-stained round spots appear on the bark. Slightly uplifted, there is a moist sensation in the hand pressure, and then the dry skin shrinks into small spots, dark brown. The disease mainly occurs in the middle and lower parts of the trunk, and when severe, it spreads to the upper part of the trunk and branches. The most serious victims are newly planted saplings, which have a high incidence of diseased plants and a large proportion of the total surface area of ​​lesions. 2. The onset of the disease occurs with mycelia and immature fruiting bodies in the diseased tissues. The occurrence of conidiospores and mature conidia in overwintering lesions became the main source of infection in the year. The onset of disease began in April of the following year, and the first peak of onset occurred from late May to June. In July-August, when the temperature increased, the disease slowed down. In September, the second peak appeared and stopped after October. The temperature begins to rise above 10°C in spring and the relative humidity exceeds 60%. The most suitable disease is at 24°C to 28°C. Pathogens enter from wounds or lenticels, and the incubation period is approximately 1 month. It takes 2 to 3 months from onset to the formation of conidia. The debilitating tree condition is conducive to disease. Untransplanted seedlings are generally not affected or lightly diseased. Once transplanted, the water loses its balance, the tree vigor is weak, and the disease is prone to occur. The peak incidence in spring is the result of the infection in the fall of last year. The number of seedlings in seedlings is closely related to the incidence of young trees in the new woodland. Drought and slim site conditions are important causes of morbidity. The large number of seedlings at the time of raising seedlings and the loss of water in seedlings during afforestation are the intrinsic causes of the initial saplings being susceptible to disease. Different species and strains of poplars have significant differences in resistance to canker disease. Poplar trees are resistant to disease, and black poplar tree species are moderately resistant, while poplar trees are more susceptible to disease. 3. Control methods 1 Use anti-disease factions or varieties; do not mobilize seedlings from wards or disease gardens. 2 Strengthen seedling management. Clear diseased trees around the nursery to reduce the source of infection. Pay attention to protect the root system when lifting and planting. Reduce seedling transport time to reduce seedling water loss. In conditions where the seedlings emerge, they are immediately immersed in water for 24 hours. Spray 2.4-D on the root before planting, which is conducive to the growth of new root system, increase water absorption and reduce disease. Immediately after planting, water should be poured. 3 When afforestation in sandy land, a plastic film covering 1 meter and 1 meter in the root of the sapling is conducive to the maintenance of soil moisture and the increase in ground temperature. Accelerate the growth of new roots. Adding water-absorbing agents to the soil is beneficial to the maintenance of soil moisture, and all the saplings under drought conditions have the function of reducing disease. 4 chemical control. In the fall (early September), seedlings that are to be planted in the coming year are commonly sprayed with 70% thiophanate-methyl 200-fold solution to reduce the amount of seedlings carried by the seedlings. Before seedlings are planted, they are sprayed with 70% thiophanate-methyl 100-fold solution or Apply dry.