With the expansion of poplar planting areas, pests and diseases of poplars also show rapid development. Recently, some readers telephoned the fast-growing poplar trees why they died in large numbers. Now we briefly make a brief statement of the situations we have seen for reference.
First, woodland varieties are mixed. In the same forest plot, because of the variety of varieties, the characteristics of different varieties make the individual growth and development status of the plants different. Some species have tall crowns and some species have short crowns. In the first and second year of life, the light in the forest is still good, and each single plant is still able to develop normally; after three or four years, the canopy is handed over, the big tree continues to prosper, and the dwarf tree gets worse under the light condition, so the growth is getting weaker and it will die. Fast-growing poplar afforestation must increase the purity of the varieties, and the grades of the seedlings are the same, so that each individual plant grows neatly and consistently to avoid differentiation among the plants.
Second, the planting density is too high. Some forest varieties are of good purity and have a neat growth in their early stages. However, due to the excessive planting density, for example, 2 meters and 3 meters, more than 100 trees per acre. In the first and second years, students are still acceptable. From the third year onwards, they are densely packed. The competition between the strains grows, causing size differentiation, and the weak plants gradually wither. Therefore, planting density should not be too large. The plants that have been planted should be harvested in time, so that each individual plant has a large growth space, and the potential for individual production increase is fully utilized.
Third, root diseases. We have seen several cases of dead seedlings and dead trees due to the disease of the purple striae of the roots. The diseased forest patches are mostly viscous and watery, and some are formerly hedgehogs and fruit trees. Before afforestation, it should be ascertained whether there is any root disease in the former oak forest. When planting and after planting, the soil should be disinfected at the roots of the seedlings and at the planting hole. The forest should pay attention to drainage and implement single-hole irrigation.
Fourth, poplar rot disease. The 84k poplars, triploid furrows, and Zhonglin 46 were all seen due to rot. The diseased forests are poorly managed and grow weakly. Strengthen management, increase tree vigor, and increase disease resistance. When the disease is mild, the diseased branches should be cut off in time, the lesions should be scraped off and the drugs should be disinfected, and the branches can be sprayed and protected. Attention should be paid to improving the health conditions of forest lands and dealing with the diseased branches in time.
Fifth, poplar canker disease. Poplar canker disease generally occurs, affecting the growth of young trees, but occurs only when heavier, and when the lesions are contiguous, the trees are killed. Different varieties have different degrees of disease. The l35 Yang disease is very light, and Zhongtian Yang is extremely susceptible. Strengthen management, promote prosperity, and increase disease resistance. In the season of spring and autumn, trunk spray 100 times thiophanate-methyl and other fungicides can control the spread of diseases.
Sixth, iron deficiency yellow leaf disease. In the alkali and individual varieties, the deficiency of yellow leaf disease is serious, and the leaves yellow, white, and scorch, resulting in dead trees and seedlings. Especially in the north of the Yellow River, moderate salinity and alkalinity occurs. European and American poplars and American poplars are heavier than poplar varieties. The application of organic manure, application of physiological acid fertilizers, and irrigation of water in reservoirs in southern mountain areas can improve the soil environment and improve soil iron supply. Seedlings, saplings can be sprayed on the surface of iron fertilizer.
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