Poplar is the main engineering tree species in northern North China. It is also a landscape tree species for parks and green areas. It is also a major species of street trees. Frost cracking is a common and frequently occurring disease of poplars, which often causes a large number of dead plants. New transplants are particularly serious.
First, the symptoms
Poplar tree cracking is known as poplar tree-breaking disease in arbor cultivation. The disease mainly damages the poplar trunk and sometimes damages the main branch. Usually from the trunk of the west, southwest of the smooth and burr hole cracking, generally the first crack in the cortex, severe cracks can reach deep into the xylem. In the spring of the next year, the trees sprouted and the sap flowed out from the frozen cracks, which became rusty after drying. If the tree is strong, it can naturally heal when it is frozen and cracked. Frost cracks deepen and deepen year by year, sometimes up to 3 to 4 meters. Usually two kinds of situations: one is open type, after the cracking, the callus turns outwards year by year and does not heal, the trunk forms a deep groove; the other is a cracking type, the callus does not turn outwards The freezing injury is heavy and the xylem cracks deep and long. After the damage, it affects the growth of trees and induces red heart disease and rotten skin disease. Both types of damage reduced tree growth and directly affected the yield rate.
Second, the cause
In late autumn or early spring, the sudden and cold air warms up. The large temperature difference between day and night is the direct cause of frost cracking; the rapid growth of trees and the high water content are the indirect causes of frost cracking.
Third, the incidence of the law
The northern area of ​​northern China mostly occurs on the sunny side of the surface, generally on the southwest and south sides of the trunk. Due to excessive rainfall in autumn or low soil conditions, soil moisture is too high, trees grow too fast, and the water content in the xylem is high. In the same afforestation site, cracking often occurs at the same location. The severity of frost cracking also depends on the cold resistance and site conditions of the species. In general, the growth and health of the native tree species is lightly affected; the land potential for planting in sandy soil is relatively high, and the damage to the drainage system is relatively light. Newly introduced damages that are not suited to soil and climatic conditions tend to be heavier.
Fourth, prevention and control measures
1. Implement reasonable cultivation and management measures. Reasonable control of water and fertilizer, promote growth, increase tree vigor, and increase the resistance of trees are effective measures to prevent and cure this disease. At the same time, conditions should be moderately pruned to regulate the tree vigor. The cut should be coated and protected. Remove dead shoots and plants in time and remove dead branches or debilitating shoots. In terms of soil treatment, the fall soil is used to fill the base of the trunk with loose soil, and litter can also cover the base of the trunk.
2. Suitable for trees. According to the biological characteristics of poplar, it should be planted in sandy loam as much as possible, while avoiding planting in low-lying areas. It is also necessary to adapt poplar varieties with strong adaptability to local conditions for greening and afforestation. Local indigenous tree species should be used as an effective measure to prevent and treat this disease.
3. Trunk treatment. In the period from late October to mid-November, straws or sacks can be used to wrap the trunk. Fresh lime water, lime sulfur, Bordeaux mixture, etc. can be used to whiten the trunk. The trunk treatment height is 1.5 to 2 meters.
4. Set the wind barrier. From late October to mid-November, wind barriers are installed on the windward side of the trees according to the frozen orientation of the trunk. The wind barrier is 1.5 to 2 meters high and the wind barrier has a bandwidth of 5 to 8 meters.
5. Chemical control. Early cracking can be used carbendazim or thiophanate-methyl 200 times the liquid, 50 international units of internal medicine, 843 rehabilitation agent or 723 Shennong liquid applied around the cracks, have a good effect. If the diseased tissue is scratched or scraped off by scraping the old skin with a knife before application, the control effect can be improved. 5 days after application, 50 to 100 times more gibberellin is applied around the frozen crack to promote the formation of healed tissue and prevent rotten skin disease or red heart disease. Http://Content/67de2be2-601e-4750-b47b-c4fd30e58321?cType=2
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