What are the diseases of Populus euphratica in Xinjiang? Specific prevention and control methods?

Poplar trunk diseases mainly include blister canker, leaf spot, rot and bacterial canker, which are the main trunk diseases of poplars. Poplar can be infected with these diseases from seedlings, young trees to big trees, but seedlings and young trees are most seriously affected, resulting in dead branches or whole plants.

Poplar vesicular ulcers occur on trunks and branches, and there are three symptoms. In Populus euphratica varieties, blisters with a diameter of about 1 cm are mostly produced around the lenticels; In poplar varieties with rough skin, blisters are usually not produced, but local small necrotic spots are produced; When the disease occurs in the wounds, dead buds and frostbite of cadres, large long or irregular necrotic spots are formed. Spring is the most important occurrence period of poplar blister canker, especially after transplanting. Poplar grows vigorously in summer, and the disease develops slowly, and the second peak can appear in autumn. Poplar is prone to diseases due to poor cultivation and management, insufficient water and fertilizer, unbalanced nutrients and weak growth.

Dothichiza populea Sacc。 Poplar leaf spot canker mainly occurs in the wound and bud mark of trunk. The initial lesion is dark brown in water, and then it forms spindle, oval or irregular lesions. The phloem tissue of the diseased part festers, and the xylem under it can also turn brown. Old disease spots can expand year after year, and multiple disease spots are connected into pieces, resulting in dead branches and dead shoots. Generally, the onset begins in mid-April, and the peak period is May-June. The disease slowed down from July to August, and new lesions appeared in September, and stopped expanding after 10 months. Generally, shallow-skinned trees are more susceptible to diseases than coarse-skinned trees, and coarse-skinned trees have a higher degree of cork and bacteria are not easy to invade. Sunburn is conducive to the invasion of germs, and the number of diseased spots on the positive side of the trunk is more than that on the negative side. When poplar grows weakly or the soil is dry and the water content is low, the disease is serious.

Poplar canker. Also known as poplar skin rot and poplar skin rot, it causes cortex rot and branches wither, and in serious cases, it can cause large-scale death of poplar. In the late stage of the disease, there are many needle-like black protrusions, that is, conidia of pathogenic bacteria, from which orange tendril-like conidia can be squeezed out under wet conditions. Conidia and ascospores of poplar bark rot spread to the host cortex through wind, rain and insects, and most of them invaded through wounds. Young trees, twigs and weak branches with wounds are more likely to get sick. When the moisture content of bark is less than 60%, the disease is serious.

Erwinia is a bacterial canker of poplar, which mainly harms trunks and branches. At the early stage of the disease, an oval tumor with a diameter of about 1 cm was formed in the affected area, and the appearance was smooth, and then it gradually became a spindle or cylindrical tumor. The color becomes grayish brown, the surface is rough, and longitudinal cracks appear. In summer, brown mucus will flow from the cracks in the affected area, which is very unpleasant. The phloem in the tumor turned brown-red, and the xylem changed from white to gray and then to red. When the disease is serious, it will rot, trees will grow weakly, and wood rot will become useless. If it is serious, the whole tree will die. Big trees suffer more than small trees, and low-lying forests are seriously ill. Trees pruned in summer are more likely to get sick than trees pruned in spring and autumn, and frostbite and pruning wounds are easy to cause diseases. Trees with untidy pruning and high stubble are also prone to illness.

Control methods: (1) Fungal ulcer control: ① Selection of disease-resistant varieties. According to the experience of poplar planting in this area, disease-resistant varieties should be selected, and newly introduced varieties should not be blindly popularized before passing the regional cultivation test. ② Strengthen the cultivation and management of young poplar forest land. Improve site conditions, remove dead plants and branches in time, trim and thinning in time, and control stem borers. (3) Follow-in, transportation and planting should be carried out in time after emergence to reduce water loss before planting. Water immediately after planting, or soak for more than 24 hours immediately after emergence. (4) Scraping the diseased spot: For diseased trees with strong disease resistance, the bark of the diseased part can be cut longitudinally with a knife or nail plate at a distance of 3-5 mm, slightly exceeding the diseased spot and reaching the xylem. Then use a brush to mix the selected chemicals (10% alkaline water, wuningmycin, non-dephenolized oil washing stock solution, 10% shuangsanling 10 times solution, 70% thiophanate-methyl 100 times solution, 50% carbendazim/kloc-. ⑤ Chemical control. Before the peak of the disease, 50-80 times diluted 1% Quefuling can be applied to the lesion or injected directly with a syringe. Trunks and branches can also be sprayed with 70% thiophanate methyl 100 times solution, 40% carbendazim 50 times solution or 2: 2: 100 bordeaux solution to prevent the invasion of germs. At the end of autumn, white paint is applied to the lower part of the trunk (the ratio of quicklime, salt and water is 1:0.3: 10). (2) Prevention and treatment of bacterial canker: ① Before poplar seedlings were cut, the cuttings were soaked with streptomycin (600 mg/kg) for 24 hours. Sick slimness must be scraped off and disinfected with 300 times formalin solution. ② Apply protective agent. For transplanted seedlings, white coating should be applied in early spring, or 0.5 Baume sulfur mixture or 1: 1: 160 bordeaux mixture should be sprayed to prevent infection. (3) Spraying streptomycin (600 mg/kg) and tree antifreeze protective agent (1l0 times) on poplar seedlings before germination in early spring or after defoliation in autumn to prevent poplar seedlings from freezing injury and increase disease resistance.