Also known as carcass blight, chestnut blight, rotten skin disease. This disease is a worldwide chestnut tree disease, the most widely distributed, the most harmful. In recent years, individual chestnut gardens have occurred in Beijing. When the disease is severe, it causes the bark to rot, wither the branches or the whole tree to die, and sometimes causes the death of large areas of chestnut trees, which is a dangerous disease in the current chestnut production. 1. Symptoms Mainly harm the main trunk cortex part of the chestnut tree, which occurs less on the branches. After the victim felt sick, it was initially reddish-brown and slightly sunken. When between June and July, many small nodular protrusions appear on the lesion, and the protruding epidermis is broken through and first appears yellow, and then becomes brown spots. When the disease does not reach the trunk for a week, the plant is still able to germinate, flower and bear fruit. As the spots continue to expand and invade the trunk for a week, the upper leaves of the plant wilt and then gradually die. When the plaque edematous protrusion is not dry, the interior is wet and rotten, there is a wine smell, and the surface of the bark disease site is rough or cracked after drying, and the orange disease tissue in the skin can be seen. 2. Occurrence law Generally from April to September and October is the peak period for the development of pathogenic hazards. Some chestnut trees have a disease of 1 month, and the whole plant dies. It is mainly transmitted by wind, rain, insects and other pathogens. In early spring, the temperature difference between night and night is large, and the sunny side of the trunk is often caused by frost damage; All kinds of wounds, such as those caused by the graft interface, mechanical damage and insect infestation, are susceptible to infection, especially the grafting interface. Plants with too thin soil and weak tree growth are also susceptible to disease. 3. Prevention and control methods (1) Quarantine and disinfect seeds and seedlings for strict quarantine and disinfection, and strictly prevent the introduction of pathogens. (2) Strengthen cultivation management and breed disease-resistant varieties; In the barren chestnut orchard, soil improvement and increased organic fertilizer are applied to enhance tree potential and disease resistance. (3) Protect the branches and roots of the tree body and paint the trunk white in late autumn; Timely treatment of insects, protection of the graft and avoid all other mechanical damage. (4) Scraping to cure disease spots, disinfection and protection In the epidemic season, timely inspection and sawing off dead branches; In the initial stage of the disease, first scrape off the coarse bark of the diseased part, apply 400 to 500 times carbendazim or antibacterial agent, apply the drug every 15 days, a total of 5 times, the inhibition rate of 100%.
Also known as chestnut brown spot disease. It is distributed in The West of Hebei and other chestnut-producing areas. 1. Symptoms are more complex, mainly manifested as the following. (1) The inner and outer seed coats of the black spot type are mostly normal, and a very small number of chestnut fruit tips become brown and black, resulting in necrotic spots of different sizes and irregular shapes on the surface of the seed kernel, black brown, gray black to charcoal black. The disease part is deep into the seed kernel, and the section is gray-white, brown, gray-black, charcoal-black, etc. When the disease is severe, there are irregular cracks in the section of the disease grain that are grayish white and gray-black. (2) Brown spot type The surface of the seed kernel forms a brown necrotic spot of different shades, which goes deep into the inside of the seed kernel, and the cut surface is white, light brown and yellow-brown. Some of the diseased grain sections have gray-white to gray-black striped voids. (3) Rotten type Seed kernels are brown or black dry rot or soft rot. Among the above symptoms, the first two types account for about 90%, and most of them are brown spot type in the early stage, and most of them are dark spot type in the later stage. 2. Pathogenesis Diseases began to appear in the near-ripening stage of chestnuts, but the incidence was lower, and there were slightly more diseased grains in the mature to harvesting period, and the disease worsened rapidly in the process of sand storage and storage at room temperature, and reached the peak of the disease after 15 to 25 days to the processing period, and then the disease no longer increased due to the decrease in temperature. The occurrence and development of diseases is closely related to temperature, degree of chestnut loss, severity of occurrence of chestnut wasps, tree age, tree potential, chestnut fruit ripeness, mechanical damage, etc. Surface dehydration of chestnut kernels is an extremely important reason for the accelerated development of the disease. The temperature of sand storage is about 25 °C, which is conducive to the development of diseases, and has a significant inhibitory effect below 15 °C, and basically stops developing below 5 °C. Temperature mainly affects the development of the disease by affecting the degree of water loss on the surface of the chestnut kernel, but excessive water loss has no significant effect on the development of the disease. Chestnut trees that are old and weak, have heavy harm to chestnut bees, are precocious and early harvested, lose a lot of water during storage and transportation, and are seriously damaged, and the disease is often aggravated. Juvenile, robust, mild insect infestation, late maturing and late harvesting, less water loss chestnut tree disease is light. 3. Prevention and control methods (1) Strengthen the management of fruit trees, enhance tree potential, and improve disease resistance. (2) Reduce the temperature during the storage and transportation period and maintain the normal water content of chestnut kernels. After the chestnut is planted, it is quickly collected, the disease and insect grains are removed, and the wet sand is hidden in the dug ditch on the same day, the width of the ditch is 40 cm, the depth is 1 meter, the length depends on the number of chestnuts, and the soil is 20 cm thick. The sand-to-chestnut volume ratio is 1:1, and every 1 meter is buried in a vent hole (a sorghum stalk with a diameter of 8 cm thick), exposing 30 centimeters to the ground. Or quickly store in a cold store, first 15 °C, then down to 5 °C. (3) Timely control of pests such as chestnut tumor bees and reduce chestnut mechanical wounds.
It is an important disease of chestnut fruit and occurs in all cultivation areas. However, due to the different cultivars, years and tree ages, the degree of victimization is also significantly different. The disease caused a large amount of fruit rot during the early shedding and storage period of chestnut poncho in the field, which could not be eaten, and also endangered new shoots and leaves, causing significant losses. When the damage is severe, the incidence of chestnut fruit is usually more than 10%. The disease is also more severe in Japan and the United States. 1. Symptoms Mainly harm the fruit, but also harm the buds, branches, leaves. (1) Generally after entering August, some of the purries on the chestnut and the base of the shell begin to turn black-brown, and gradually expand, until the harvest period all chestnuts become black-brown. Sick chestnuts are smaller than healthy and fall off earlier. Chestnut fruit onset is later than chestnut poncho, mostly starting from the top of the fruit, some from the side or bottom, the skin of the affected part of the fruit becomes black, often attached to the gray-white hyphae. After the germ invades the kernel, the seed kernel becomes dark brown, and as the symptoms develop, the seed kernel rots and atrophies, creating a cavity, the inside is filled with gray-white hyphae, and finally all the seed kernels become dry rot and cannot be eaten. Some of the fruit is saprophytic by other fungi and is softly decayed. (2) Leaf damage mostly occurs after the middle of summer, the spots are irregularly shaped to round, brown or dark brown, often with reddish-brown fine edges, and many small black spots; After the buds are killed, the diseased part becomes brown and rots, and the new shoots eventually die; After the twigs are killed, they are vulnerable to wind breaks, and the victim chestnuts mainly appear brown spots at the base. 2. Occurrence of mycelium lurking in the buds and branches of living organisms overwintering. The diseased leaves and fruits on the ground are wintering places. When the conditions are right, the ascomycete shell can grow in October and November, and from April to May of the following year, a black conidia disc grows on the twigs or branches, and the conidia are spread by wind and rain or insects, and directly invade the percutaneous hole or from the epidermis. The pathogen begins to infect Chestnut from the young fruit stage shortly after flowering, but only the symptoms of the disease progress rapidly in the late growth stage. Germs can also invade through stigma during the flowering period, causing chestnuts and seed kernels to become ill after August. No re-infestation during storage and transportation. After harvesting, chestnuts and chestnut fruits accumulate in large quantities, and if they do not dissipate heat quickly, they will rot seriously. The severity of the disease is closely related to the variety. Weakened trees caused by old trees, dense plantations, inadequate fertilizer and damage to roots and trunks are severely affected. Trees with dead branches, dead leaves and chestnut gall bees tend to have a heavy disease. The formation period of chestnut canopy is wet and rainy, which is conducive to the occurrence of disease. 3. Prevention and control methods (1) Combined with winter pruning, keep the chestnut tree ventilated and transparent, cut off over-dense branches, diseased dead branches, and burn them in a concentrated manner. (2) Strengthen soil management, appropriate fertilization, enhance tree potential, and improve tree disease resistance. (3) Spraying agents such as disease-killing, carbendazim, or half-volume Bordeaux liquid, especially in April and May, a large number of bacterial sources are controlled. After winter garden clearance, a 50% carbendazim wettable powder 600 to 800 times liquid is sprayed. From April to May and early August, spray the following agents once each: 0.2 to 0.3 Baumedo stone sulfur mixture, 0.5% lime half-weight Bordeaux liquid; 65% Zinc Desen Wettable Powder 800 times liquid.
Powdery mildew chestnut has two symptomatic features. The first is powdery mildew, which can harm chestnut leaves, shoots and buds, and is characterized by a layer of gray-white powder mold on the surface of young tissues such as disease-susceptible leaves, shoots and buds. The white powder layer on the affected leaf can grow on the front or back of the leaf. The second is powdery mildew, where irregular faded green macula can be seen from the foliar surface at the beginning of the disease. Then, a pale grayish white mycelium and a white powder layer are produced on the back of the leaf. After autumn, it produces a pale yellow → brownish yellow → black-brown small globules on the white powder layer, that is, a closed capsule shell. The young shoots of the disease have a gray-white powder layer on the surface, and then dry up, the young shoots are affected, often the leaves cannot be elongated, and if the young leaves are locally diseased, they are usually twisted and deformed. 1. Causes and regularities Pathogenic bacteria overwinter in chestnut disease leaves, diseased shoots or soil with closed capsule shells. In the spring of the following year, ascospores are released from the closed sac shell, and the air current is transmitted to the young leaves and young shoots for initial infestation, and the chestnut seedlings are too dense, low-lying and wet, poor ventilation and light transmission, and insufficient light, which is conducive to the infection and epidemic of pathogens; Nitrogen fertilizer is applied to the garden and phosphorus and potassium are insufficient, and the seedlings grow and have a serious disease; The resistance of different chestnut cultivars to powdery mildew varies significantly. 2. Prevention and control measures (1) When tending and managing in autumn and winter, pay attention to completely removing diseased leaves from the diseased woodland and pruning the diseased branches; The nearby diseased chestnut and oak plants are also managed; Till woodland or nursery soil to reduce overwintering pathogens. (2) Newly developed chestnut orchards should select disease-resistant and productive varieties, and grafted seedlings should be adopted. (3) Reasonable fertilization of the nursery land, no partial application of nitrogen fertilizer, severely affected areas should be increased to increase the appropriate amount of phosphorus and potassium fertilizer, improve the resistance of seedlings. (4) Seedlings and young forests, spray 0.2 to 0.3 Pomeruite sulfur compound at the beginning of the disease, once every half a month, each time 1500 kg / ha (1 ha = 10000 meters 2), insist on spraying 2 to 3 times, in the summer can be changed to 1% Bordeaux liquid. In addition, during the powdery mildew epidemic season, spray 50% carbendazim wettable powder 1000 times liquid, 50% methyl tolbuzin wettable powder 800 times liquid, 50% antibacterial special wettable powder 600 times liquid, 50% Leyte wettable powder 1000 times liquid.
Chestnut plaster disease is one of the common diseases in the chestnut producing areas of the provinces south of the Yangtze River Basin in China, which harms the branches, and occurs to varying degrees in the old chestnut forests and young forests, and the general old branches are more seriously affected. There is a brown velvet hyphae membrane on the affected branches, which is round or irregularly shaped and tightly attached, so it is called plaster disease, which is initially gray-white and gradually turns brown. In severe cases, the branches die, affecting the growth and development of fruit trees. 1. Occurrence of regular occurrence The pathogen overwinters on the affected branch with a bacterial membrane, and in May of the following year, the basidiotium and basidiospores are produced. The spores spread through insects such as wind and rain and mesenchymal insects. The hyphae penetrate the cortex or invade the interior of the branches and holes to absorb nutrients. Mycelium grows and develops on the surface of the branches, gradually expanding to form a bacterial membrane. The plastered fungus symbiosis with the quercus shield borer, which is harmful to the chestnut tree, grows and develops by using the secretions of the insect as nutrients, and the insect is protected by the bacterial membrane and can multiply and spread. Therefore, the occurrence and development of diseases is closely related to the extinction of insects. The spatial distribution of pathogens and insects is consistent, most of them gather at branch forks, leaf marks, cracks and other backlit places; The occurrence period is also consistent, from April to May and September to October every year, it is not only two obvious growth periods for the expansion and number of plaster disease spots, but also the reproductive and spread periods of the first and second generations of Quercus quercus shield bug. In addition, the area of disease distribution is also directly related to the dependence of pathogens on the main vector of transmission and the provision of nutritional conditions. The ecological environment of chestnut trees has a certain impact on the occurrence of this disease, generally occurs in mountainous or semi-mountain chestnut forests, and in the mountains, slopes, and slopes next to river ditches that are shaded by the sun, the chestnut forests with little light and high humidity have serious diseases.
2. Prevention and control methods The control of the disease should take comprehensive measures including strengthening the management of chestnut forests, eliminating mesozoans and selecting excellent disease-resistant varieties. (1) Strengthen the management of chestnut forests The cultivation of chestnut trees should be adapted to local conditions, and chestnut trees should not be densely planted in valleys, rivers and depressions. Timely care and management, strengthen the pruning of the whole branch of the chestnut tree, in order to facilitate ventilation and light transmission, remove weeds and shrubs, reclaim and replant crops, increase fertilizer, promote the growth of chestnut trees, and enhance the ability to resist diseases. (2) Extermination of mesozoans This is an important measure to prevent plaster diseases. Commonly used agents are 5 to 15 times the diesel emulsion (diesel 1 kg, soap 25 g, water 0.5 kg), 1 to 3 baume degrees of stone sulfur compound, 20% lime milk, etc., the method of application is brushing and spraying, and the former has the best effect. (3) Select excellent varieties of disease resistance Promote the planting and grafting of excellent varieties with strong disease resistance, high yield and stable yield, such as sticky bottom plate, dahongpao, etc., give full play to the disease resistance of the chestnut tree itself, reduce the application of drugs or do not apply drugs, in order to achieve the purpose of reducing or avoiding the harm of plaster diseases, which is the most economical and effective measure.