Poplar rot disease and its control
Poplar is a generic term for deciduous trees of the genus Populus in the genus Populus. There are more than 100 species in total, which are mainly distributed in the temperate and frigid regions of Europe, Asia, and North America as well as countries along the Mediterranean coast and the Middle East. There are more than 50 kinds in China. Wood is used as a civil building material, producing furniture, matchsticks, sawn timber, papermaking, etc. It is also a wood-based board and fiber material. The leaf is a good feed. Poplar is also the main species of timber forest, shelter forest and greenery on all sides.
Over the years, China has made many achievements in poplar science research. It has successfully introduced and selected a number of excellent clones of poplar trees. After large-scale promotion, it has formed huge productivity and remarkable economic benefits. The combination of high-yielding cultivation techniques into high-yield cultivation patterns and supporting technologies has shortened the rotation period and improved the yield and quality of wood. In the prevention and control of poplar pests and diseases, some really effective methods and comprehensive prevention and control techniques have been proposed. Due to the adoption of excellent poplar varieties and middle-class cultivation measures, in the past more than a decade, China's newly-created poplar plantation has increased its yield per unit area, and the rotation period has also been shortened.
In recent years, due to the implementation of the State's returning farmland to forests and the implementation of the “Three-North†shelter forest afforestation project, many provinces and cities have built a large number of poplar-producing forests during the construction of the project. Now the area of ​​poplar plantation is about 6 million hectares. It accounts for 19% of the total area of ​​the country's plantations and is 4 times the area of ​​poplar plantations in the world. Because poplars are susceptible to pests and diseases, engineering results are difficult to consolidate or even fail.
In recent years, rot disease (also called rotten skin disease) is the main cause of death of poplar trees. Most poplars, especially fast-growing varieties, may be infested.
First, poplar rot disease symptoms. The stems and branches of Yang are the sites of rotten skin disease. There are two types of dry rot and dry shoots.
1. Dry rot: Occurs mainly on the main stem, branch and bifurcation. In the early stage of disease, it is dark brown, with spots of water stains, slight swelling, cortex tissue rot and soft, subcutaneous smell of distiller's grains, leakage of water by hand pressure, loss of underwater depression, and sometimes diseased bark of the bark, or even become Filamentous, lesions sometimes have distinct dark brown edges. Under suitable conditions, vertical expansion is faster than horizontal. When the diseased part encircles the trunk for one week, the above parts will die, the cortex will rot, and the fibers will be separated like hemp. It will also change color from the sapwood of the xylem. A large number of needle-like protrusions were produced on the late stage lesions, namely the pathogenic conidia. On wet days, yellow, orange, or red filamentous conidiophores were extruded from the conidial orifice.
Blight disease mainly occurs on seedlings, saplings and large branches. At the beginning of the disease, it was dark gray, and the diseased part expanded rapidly. After wrapping around for a week, the upper shoots died.
Second, poplar rot disease source and the law of incidence
The disease is mainly contaminated dermatophyte of the Ascomycetes subsp. genus, and the anamorph of the disease is golden yellow crustaceans of the semi-known fungus subphylum. Mycelia and immature fruiting bodies are wintered in diseased tissues. The occurrence of conidiospores and mature conidia in overwintering lesions became the main source of infection in the year. The onset began in April of the following year, and the first peak of onset occurred from late May to June. In July and August, when the temperature increased, the disease slowed down. In September, the second peak appeared. At this time, the germs originated from the conidiospores formed in the spring of that year and stopped after October. The temperature in spring is above 10°C, and when the relative humidity is above 60%, the disease begins to occur; at 24-28°C, it is the most suitable disease. Pathogens enter from wounds or lenticels, and the incubation period is approximately 1 month. It takes 2-3 months from the onset to the formation of the conidial phase, and cysts and ascospores form in the lesions in the fall. Latent infection is an important feature of poplar canker disease. Ascospores spreads on the host's cortex by wind and enters the wound. After the winter, the disease is obvious. When the tree vigor is weak, it is conducive to disease. The lesions that developed on robust trees that year were able to heal naturally in the following year. The same disease tree, Yang surface lesions more than the dark side. Untransplanted seedlings are generally not affected or lightly diseased. Once transplanted, the water loses its balance, the tree vigor is weakened, and the disease easily occurs. The peak incidence in spring is the result of the infection in the fall of the previous year, not the spring of the year. During spring afforestation, new lesions on the initial planting young forest were also the result of infection in the nursery the first year. Therefore, the number of bacteria in seedlings is closely related to the incidence of saplings in new forest lands. Drought-inducing site conditions are an important cause of morbidity, and are also the main reasons for the particularly prevalent and serious ulcer disease in the “Three North†areas of drought and semi-arid in China. 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 tree species are more susceptible. The vast majority of hybrid strains of the Qingyang School and the Heiyang School are also susceptible to disease. Qing Yang, Xiao Qing Yang, Yang Yang and Beijing Yang are all highly susceptible poplar trees. Among the factions that are resistant to disease, some strains are susceptible, such as Populus tomentosa is a more resistant tree species, and some of them (triploid Chinese white poplar) are very susceptible. There are also disease-resistant strains in susceptible types. At the same time, the susceptibility of tree species is closely related to the environmental conditions in which they are located.
Third, poplar rot disease prevention and control measures. Increasing the growth of trees and increasing the resistance of trees is the fundamental way to prevent and treat this disease.
(1) Select the appropriate soil and variety when planting, so that the appropriate tree is suitable. Strict technical regulations to improve disease resistance. (2) Cultivate strong seedlings. The cuttings should be stored in the cold place below 2.7°C to avoid reducing the vitality of the cuttings, avoiding the long-distance transportation of seedlings, serious prosthesis, digging roots for more than 24 hours or afforesting mud before afforestation. (3) Care management after planting, prevention and control of stem pests, reasonable pruning does not leave stubs. Pruning should be done in the winter to avoid pruning in the rainy season. Avoid strength pruning. The sawn cut should be sterilized with lime sulfur, or coated with diammycin or sprayed in high concentrations. (4) Poplars that are seriously affected should be promptly removed and burned to prevent the spread of germs. The severely infected stands were completely cleared to prevent the formation of new sources of infection and to infect more areas of forest. (5) Strengthen management of woodland management and promote vigorous growth of forest trees. Before entering the winter season or before the propagation of the germs in the early spring, spraying a high concentration of bactericide on the trunks of young trees, middle-aged forests must apply fungicides, lime sulfur, or Bordeaux mixture on the trunks to prevent disease and treat diseases. Diseased trees should first scrape off the lesions and then apply them with better results. Practice has shown that 15 days after the application of fungicides at the site of the disease, there is a clear healing of the new myogenic wounds. (6) For plants or forests with lesser susceptibility, in order to strengthen management and increase the growth potential of the trees, scrape the lesions with a knife and scrape them to the health department, and then spray dry or dry them. The optional chemical agent is 10 times the edible alkaline water, or 20% of the agricultural anti-120 water agent 10 times, 50 times 40% of the United States arsenic, 50% of the 100 times tetrazine, 5% thiophanate, carbendazim, etc. Apply 2-3 times.
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