Author: Joe Wang Yichang Wei Kong gold deposit from Zhu Lisheng Xu Gu is cultivated yam yam Dioscorea can form fleshy underground tubers, annual or perennial twining vine, official organ tubers product. The flesh is pure white, sweet and fragrant, and has a large quality. It is a good vegetable that is eaten, and it is a commonly used medicinal material. It is recognized as a pollution-free vegetable. The development of yam production is a good project to promote the adjustment of agricultural structure, develop high-efficiency agriculture and increase farmers' income. The development prospects are very broad, but in the cultivation process, due to lack of experience or non-standard cultivation techniques, there are often some or all kinds of problems. The following common diseases and control techniques in the cultivation process are described as follows: (1) Red spot disease 1. Symptoms The yam erythema disease is a disease caused by nematodes and mainly damages the root tubers of yams. The infected tuber is small and light in weight. At the beginning of the onset of yam erythema was the formation of a red-brown near-circular to irregularly slightly depressed lesion on the tuber, with a single lesion of 2 to 4 mm in diameter. When the disease is heavy, the lesions are dense and dense, and they merge into each other to form large dark brown plaques. The surface has fine-spotted lesions ranging from 2 to 3 mm in depth and up to 1 cm in depth and brownish to dry rot. 2. Transmission routes and disease conditions The yam nematode can survive in the soil for more than 3 years. The diseased debris and diseased field soils are the main route of erythroderma infection. The life cycle of yam nematode is extremely irregular. It takes about 2 generations a year, and only infects yam. When new tubers begin to form in June, the nematode can infect, and the infection gradually increases until it is harvested. The nematode grows from the base to the long. Can be infected at 40cm, with more than 20cm lesions. 3. Control methods (1) Crops that are not easily infested with wheat, corn, sweet potatoes, potatoes, cotton, tobacco, peppers, carrots, watermelons, etc. should be cultivated for more than three years. (2) With 0.1%~0.3% TMK dip diseased plant for 24 hours, the disease prevention effect reached more than 95%; in the case of heavy planting, 2kg of TMK granules per 667m2 furrow before sowing, the control effect reached over 75%. (3) Selecting propagation-free propagation of planted fields, combined with comprehensive measures such as rotation and application of non-hazardous fertilizers. (b) Anthracnose 1. Symptoms mainly affect the leaves and also harm stems. On the leaf veins of the leaves, small patches of primary brown depressions turn dark brown later, and after the enlargement, the central spot of the lesions is brown, and the surface of the lesions is scattered with small black dots (spore disks). The incidence of vine vines was more in the near part of the ground. The lesions were dark brown and slightly sunken. When the damage was serious, the leaves fell early and the vines died, causing the plants to die. Spots on leaves or vines often produce pale red sticky material (conidial blocks) when the air is wet. 2. Pathways and Pathogenicity Anthracnose is a disease that is caused by infection with Staphylococcus aureus and Dioscorea solani. The pathogenic bacteria mainly overwintered within the diseased tissue of the mycelia, and the conidia were transmitted through wind and rain, and the onset was heavy in high temperature and rainy season. 3. Control methods (1) Agricultural control: Infested plots are applied for more than 2 years of rotation; after harvest, the sick and residual bodies left in the fields are burned and burned, and the soil is deep-turned to reduce the source of overwintering bacteria; high-bay management is used to improve the field. Microclimate; Strengthen field management, timely cultivating and weeding, loose soil drainage, reasonable close planting, improve ventilation and light transmission, reduce field humidity; Rational fertilization, mainly organic fertilizer, appropriate application of phosphorus and potassium fertilizer, less nitrogen fertilizer, strong cultivation Seedlings, enhance plant disease resistance, too much nitrogen fertilizer will cause plants to be tender, and susceptible to disease. (2) Disinfection of the plant: Before sowing, soak 50% carbendazim WP 500 to 600 times or soak the yam. (3) Chemical control: After emergence, spray Bordeaux mixture of 1:1:50 for prevention. Spray once every 10 days for 2~3 times. 58% of metalaxyl-manganese zinc wettable agent and 25% of Ledomil WP 800 to 1000 times after the onset, 80% of anthraquinone omeprazole WP 800 times, 70% of A Jitobuzu WP 1500 times, 50% acetaminophen 1000~1500 times, 77% can kill 500~600 times, or use Tribemic bactericide (with prevention, treatment and eradication) 7d once, Even spray 2 or 3 times, spray rain and timely spray. (C) Brown spot (also known as gray spot or brown spot larvae) 1. Symptoms mainly damage the leaves. The leaf spot appears on both sides of the leaf, nearly circular to irregular shape, the size varies from host to host, usually 2~21mm, the center of the leaf spot is grayish to brown, often 1~2 dark brown rims, some There is a yellow to dark brown water-immersed halo around the surface, and when the temperature is high, there is a gray-black mold layer on the lesion. The pale back color of the leaves is very heavy. 2. Transmission routes and disease conditions The pathogen of yam brown spot is the fungus of Dioscorea zingiberensis. The mycelia and the conidia of the pathogens pass through the winter on the diseased body. When the temperature and humidity are appropriate in the spring of the year of the year, the conidia spread by the airflow, and the initial infection occurs. The diseased part then produces the conidia again. Staining, infestation is mainly due to wind and rain. The disease conditions are warm and humid, especially during periods of growing up, frequent showers or yam racks are closed, ventilation, poor light transmission conditions, high air humidity, and easy incidence. 3. Prevention methods (1) After the autumn harvest, clean the pastoral area and concentrate the diseased body deeply or burn it. (2) Apply 75% chlorothalonil wettable powder 600 times or 50% carbendazim wettable powder 600 times or 50% thiophanate-methyl sulfur sulfuric acid 800 times when the rainy season arrives. (d) Leaf spot disease 1. Diseased yam leaf spot Common coal leaf spot (red spot), brown spot white spot (spot disease), grey brown spot, and brown spot disease, among which coal spot There are more illnesses. Coal-spot disease is a primary erythematous small spot on the leaf surface, which expands to a nearly circular or irregular shape, with no obvious boundary lesions, and is about 1 to 2 cm in size, sometimes converging to form large spots. The lesions of the leukoplakia penetrate the surface of the leaves, with small spots, round or irregular shapes, periwinkles, slightly convex, brown in the middle, and turning grayish brown to grayish white. The lesions of gray spot and brown spot have obvious concentric ring patterns with leukoplakia. The lesions on the back of the above four kinds of leaf spot were all gray-black moldy. Among them, there were many moldy things caused by coal-spot disease, and minor molds produced by other leaf spot diseases. 2. Transmission routes and disease conditions Four leaf spot diseases of yam are caused by fungal infections of the genus Cercospora. The pathogenic bacteria live in the field with mycelium (mould layer) attached to the diseased body of cowpea plants. The second year of spring conditions are suitable to produce conidia, with the airflow, rain spread for initial infection, causing the disease. Later in the field can be repeatedly infested, causing continuous disease. When the temperature is 25~30°C and the relative humidity is above 85%, it is easy to cause the disease. Poor ventilation, high temperature and high humidity in protected areas, and high temperature and high rainfall in summer under open conditions are all important conditions for disease development. 3. Control methods (1) Agricultural control: appropriate dense planting, appropriate increase of row spacing, and improvement of ventilation and light transmission conditions in the field; cultivation of protected fields should adopt sorghum planting, film mulching, timely ventilation to reduce temperature and humidity, and prevent excessive humidity in the field; Develop organic fertilizers, increase phosphorus and potash fertilizers, and increase disease resistance of plants; keep the fields clean, remove diseased leaves in the early stages of disease, and completely remove diseased bodies when they are pulled, concentrate on burning, and reduce pathogens. (2) Chemical control: Highlight the word “earlyâ€. At the beginning of the disease, 1:1:200 Bordeaux fluid, 50% carbendazim wettable powder 500 times, or 50% thiophanate-methyl wettable powder 500 can be used. Double liquid, or 75% chlorothalonil WP 600 times, or 58% metalaxyl-magnesite wettable powder 600 times alternate spray, spray every 5~6d, even spray 3 times. (five) Wilt disease (commonly known as dead rattan) 1. Symptoms The disease mainly affects the stem base and underground tubers. At the beginning of the disease, a rib-shaped, brownish-spotted brown spot develops at the base of the vine. Afterwards, the lesion expands continuously, causing the entire surface of the base to rot. When the surface area of ​​the rot decays quickly enough to wrap around the stalk, it causes the ground to rot. The leaves of the ministry gradually yellowed and fell off, and the stems quickly died. If the base of the stem is cut, it can be seen that the diseased part turns brown. In the case of tuber disease, round to irregular dark brown spots occur around the lenticels, and the fibrous roots and internal tissues also turn brown and dry rot, and the severely susceptible whole tubers become thin and brown. Fusarium wilt disease can continue to expand during storage, causing harm. 2. Transmission routes and disease conditions The wilaya wilt disease is caused by the fungus Fusarium oxysporum. The mycelium of the yam wilt and the original stem spores can survive in the soil for many years. When the conditions are appropriate, the germinating young shoots and yam plants can be directly invaded. The yams mouth and seed pieces can also continue to infect bacteria. If no diseased seed pieces or germinated young shoots are infected by the bacteria, it is difficult to prevent and cure them completely. The suitable temperature for the development of Fusarium wilt of yam is 13~35°C, and the optimum temperature is 29~32°C. When the humidity is high, the disease is easy to occur, so it is easy to develop in high humidity and high temperature seasons. Continuous cropping, low-lying land, field water accumulation, poor drainage, and soil-viscosity are all favorable for disease, which is a frequent occurrence in high-temperature seasons. In addition, excessive application of nitrogen fertilizer, soil acidity is prone to disease, if found, should immediately change. 3. Control methods (1) Choose a disease-free yam plant for seeding: If necessary, soak the Yamzui 10~20mm with a 70% mancozeb WP wettable powder 1000 times before planting. (2) Apply 1:50 lime slurry pre-antiseptic rotting to the incision of the yam mouth before entering the pit. (3) Application of compost made from enzyme bacteria. (4) Control of chemicals: In the middle of June, 70% of dexamethasone zinc WP 600 times or 50% of sterilizing water-soluble powder 1000 times was sprayed on the base of stems, and sprayed once every 10 days for a total of 5 to 6 treatments. Times. (6) Root rot disease 1. Symptoms The initial stage of root rot of yams is the formation of brown irregular spots on the base of vines, followed by the expansion of spots to form dark brown long lesions, depressions in the middle of the lesions, and severe vine base shrivels. Causes the vine to die. The surface of the lesion often has inconspicuous light brown filamentous mildew. The onset of tuber often results in the formation of brown irregular lesions near the terminal buds. If the roots are affected, it can cause root death. 2. Transmission routes and disease conditions The pathogen of yam root rot is the wintering of mycelia or sclerotium in the soil or on the sick and can survive in the soil for 2 to 3 years, through soil, rain, and the use of pathogenic bacteria. Fertilizer spread. It is prone to onset under high temperature and high humidity conditions, with mild onset in drought, heavy onset, and severe onset of flooding in the field. 3. Control methods (1) Collect residues and burn out as soon as possible. (2) Implement rotations to avoid continuous cropping. (3) Chemical control: At the beginning of the disease, 75% chlorothalonil WP can be used 600 times, 53.8% can kill 2,000 dry suspensions 1000 times, or 50% thiram 500 to 600 times spray. Spray once every 7~20d, continuous control 2~3 times. (vii) Brown rot (corruption) 1. Symptoms mainly harm root tubers, causing tuber rot. The symptoms are not obvious early and they are not found until harvest. When the tuber was infected, it showed a rotten, irregular brown spot. It was slightly depressed. The diseased block was often deformed, with slight rot. The diseased part became soft. After the incision, the diseased part was discolored. The affected part was larger and deeper than the external lesion. At the time of the disease, the area was completely rotted. 2. Transmission routes and disease conditions The yam brown rot is caused by the fungus Fusarium solani. The pathogenic bacteria can spread through the rain, flowing water, agricultural implements and field operations by using mycelium, chlamydospores, or conidia to overwinter on the soil, diseased bodies and plants. Long-distance transmission is mainly a diseased plant. The bacteria can survive in the soil for a long period of time and it is difficult to eradicate it once infected. The growth and development temperature of the bacteria is 13~35°C, and the optimum temperature is 29~32°C. The high temperature and high humidity are favorable to the disease. Even field crops, low crop fields, field water accumulation, poor drainage, and soil viscosity are conducive to disease. (3) Control methods (1) The disease should be completely removed during harvest and burned in a concentrated manner, and deep soil and membrane sealing should be used to disinfect the soil by high temperature, or rotation should be implemented to reduce the occurrence of diseases. (2) Choose a disease-free plant for planting. If necessary, cut the plant to dryness for 20 to 25 days. (3) Chemical control: spraying 70% thiophanate-methyl WP 1000 times and 75% chlorothalonil wettable powder 1000 times, or 50% thiophanate-methyl sulfur sulfuric acid 800 times in the initial stage of disease, Sprayed once every 10 days, continuous control 2 to 3 times. (8) Melasma 1. Symptoms at the beginning of the season are harmful to stems, young shoots, roots, and underground stems. In the later period, it mainly damaged tubers and formed irregular dark brown spots on the tubers, reaching deep into the xylem and reducing the commercial value of the tubers. 2. The transmission route and disease conditions are caused by a nematode infestation. The nematode is overwintering in the plant, diseased body and soil. The diseased plantlets and diseased plantlets are the main vectors of transmission. The nematode invades from the attachment point of the planting bud seedlings, moves up the subcutaneous layer and the marrow, and parasitizes life. Entering the tuber formation period, nematodes spread from the vine into the top of the tuber and develop in depth to the tuber. The nematode invades the natural orifices and wounds of the tubers and roots, and forms dark brown patches on the tubers. 3. Control methods Selection of disease-resistant varieties and disease-free planting, establishment of far-reaching breeding fields, and rotation of grass crops for more than 3 years; timely removal of sick plants in the field; before sowing, the plants are sun-dried after use in the sun 1: 1:150 Bordeaux liquid soaking 10min disinfection; combined with site preparation or backfilling and excavation, 20~30cm away from the surface, with 50% phoxim EC 500g per 667m2 for soil disinfection. (9)Spot blotch 1. Symptoms Leaf blight mainly damages leaves, light leaves make the leaves dry, and in severe cases, the whole plant can die. The earlier the disease, the heavier the reduction in production. The early onset of yam spot blight is to produce brown dots on the leaf surface, followed by expansion of the lesions, showing polygonal or irregular lesions, sizes of 6-10 mm. The center is brown and the edges are dark brown with black dots on it. This is the conidia of the germs. The condition continues to develop. When the disease is severe, the whole leaf is dry and then the entire plant can die. 2. Transmission routes and disease conditions Spot blotch of yam is caused by the spore fungus Dipidium spp. The pathogenic bacteria overwintered on diseased leaves with a conidial device, and when the temperature conditions were appropriate in the spring of the second year, the conidia released conidia, with the aid of wind and rain, initial infection and repeated infection. The disease can occur at the seedling stage, and the suitable temperature for the mycelium growth and conidial formation is about 25°C. Under suitable conditions of temperature and humidity, the bacteria can invade the yam leaf tissue within 48 hours. Therefore, warm and humid and cloudy, heavy fog is conducive to the occurrence of spot blight. However, if the air is dry, it will inhibit mycelial growth and spore formation. Therefore, the onset of hot and dry weather is lighter. When the temperature is above 15°C, the disease is also likely to become popular when rainy weather, lack of fertilizer in the soil, and weak plant growth occur. 3. Prevention and control methods 58% metalaxyl-manganese zinc wettable powder 500 times or 25% Lei Duomier WP 800 to 1000 times after onset of spraying; or 80% anthrax omeprazole wettable powder 800 times Liquid, 70% thiophanate-methyl wettable powder 1500 times, 50% acetaminophen wettable powder 1000-1500 times, 77% can kill particles 500 ~ 600 times liquid, 7d once, even spray 2~3 Times, spray rain after spraying. (10) Marker disease (column brown spot, white astringent disease) 1. Symptoms mainly damage the leaves and vines of yams, resulting in dry leaves and stem vines. The initial stage of the onset of the leaves is the formation of yellow or yellowish-white edges on the leaf surface that are not evident, and then gradually expand. The enlargement is often limited by the veins, irregular or polygonal, the size of 2 ~ 5mm, turned brown lesions, no ridges. The lesions on the edge of the latter stage are slightly convex, and the middle lesion is light brown, with scattered black dots, that is, conidial discs. When the lesions are severe, the lesions can be perforated or withered. However, the leaves usually die without falling leaves, so the white astringent disease and anthrax There is a clear difference in the disease. Stalk susceptibility and petiole susceptibility are similar to those of pathogenic bacteria, and oblong or irregular brown lesions may appear. In severe cases, upper and lower lesions merge together, causing stem vines to die. 2. Transmission routes and disease conditions The zebra disease is caused by the fungus, a fungus of the genus Dioscorea. The pathogenic bacteria overwintered with conidium sub-distributors and mycelium on the diseased sowing body. When the second year is appropriate, the pathogenic bacteria on the diseased body will form conidia, which will spread with the rain and rain, and will be the first in the lower leaves of the plant. Onset, the formation of the initial infection. When the pathogenic bacteria invade the stems and leaves, the mycelium grows between the cells in the stem and leaf tissue and forms the conidia disc and conidia under the skin. After the mature conidium matures, it will break through the epidermis of the stem and leaf when encountering suitable humidity and temperature. After 1 to 2 days of incubation, the conidia can germinate again and spread the disease. The suitable temperature for onset of yam speckled disease is 25~32°C, so it is easy to develop in high temperature and rainy season. The disease is most severe from mid-July to mid-August, and can continue until harvest. The incidence of speckle disease is related to the amount of nitrogen fertilizer applied, and it is prone to onset when there is too much nitrogen fertilizer. 3. Control methods (1) Implement rotations to avoid continuous cropping. (2) Dispose of the diseased body promptly after harvest, concentrate deeply or burn it, and reduce initial infection. (3) Advocate the use of compost made from fermented bacteria. (4) Spraying 53.8% from the beginning of June can kill 2000 times of 2000 times of dry suspension agent, 50% of Fumei double powder 500~600 times, or 1:1:200~300 times of Bordeaux mixture, spray every 7~10 days. 1 time, continuous control 2 to 3 times. (11) Root-knot Nematode Disease In recent years, with the expansion of yam cultivation area, the occurrence and spread of root-knot nematode disease of yam gradually increased. The lighter person reduced the production by 20% to 30%, and the severe person reduced production by more than 70%, and the quality of the product was obvious. The decline has severely hampered the further development of the target yam production. The hazard characteristics and prevention and control measures are described as follows: 1. Symptoms of yam nematode disease mainly damage underground tubers. There are generally no obvious symptoms in the aboveground parts, and the disease is severe. The aboveground parts show pale leaf color, weak growth, and poor luxuriant plants. . After infection of root tube nematodiasis by yam underground tubers, similar knobhead-shaped nodules of different sizes are produced on the epidermis of tubers. The tumors heal and overlap with each other to form larger nodules (commonly referred to as big cockroaches). A small amount of stubby white roots are produced on the material. The skin color at the site of the disease was darker than that of the normal skin, and it became yellow-brown. There is no significant change in the color of its internal organization. On the fine roots of tubers there are millet grain root knots. The quality of the light parts of the affected parts was reduced. In addition to the deep brown skin, the internal tissues turned dark brown and rotten, resembling dead wood, completely losing the value of food and causing great economic losses. The yam nematodes are mainly distributed in soil layers of 0-30 cm, and the incidence of soil layers below 30 cm is small. The high dryness of sandy lands in Gansu caused a severe onset of the disease and continued to affect the disease. 2. Prevention and control measures As a result of the damage of tuber root tube nematodes of yams, many large and small nodules were generated, which broke the surface soil and formed larger cracks, which was similar to the situation of breaking up the surface soil after the roots of hawthorn were enlarged. Because of the small size of nematodes, they can only be observed under a microscope. Farmers do not understand or pay attention, and therefore often ignore their prevention and control. In addition, root-knot nematodes are a kind of soil-borne diseases, chemical control is difficult, and the investment is large. At present, there is no ideal agent for the control of nematodes, so chemical control can only be used as an auxiliary measure and comprehensive control measures must be taken. (1) Plant quarantine: When transporting yam seeds, strict quarantine must be conducted. When peasants purchase or purchase yam seeds, farmers should pay attention to them. Do not introduce saplings from the wards, and do not use diseased yam seeds and choose robust yam as a disease-free yam. Breeding materials to prevent human transmission. (2) Reasonable crop rotation: Where there is a water source, a paddy-soil crop rotation is practiced, and rice is planted three to four years later. Or rotation with corn and cotton can significantly reduce the amount of nematode in soil, which is a simple and easy preventive measure. (3) Induction and killing control, reduce the density of insect population: plant some fast-growing green leafy vegetables that are susceptible to root-knot nematodes, such as cabbage, coriander, lettuce, spinach, etc., and the growth period can be harvested in about 1 month. At this time, the roots are covered with root knots. , but have little effect on the output. When the roots are uprooted at the time of harvest, the shoots are edible, and the roots are taken out of the field for centralized destruction. This reduces the amount of nematodes in the soil and is a feasible method of prevention and control. (4) Elimination of diseased organisms and application of organic fertilizers: The diseased plants are brought out of the field, concentrated in the sun, burned or buried deeply, and the weeds in the fields such as leeks etc. are eradicated to reduce the number of nematodes. Apply sufficient organic fertilizer as a base fertilizer to ensure a good supply of water and fertilizer during the growth process of yams to make them grow robustly. (5) Seed treatment: For the yams or yam segments used as seedlings, the wound (ie, the cross section) should be immediately immersed in lime powder so as to provide disinfection and sterilization. Then the preserved yam seeds are sun-dried in the sun and flipped 2-3 times a day to promote wound healing, form callus, and enhance the disease resistance and germination potential of the seeds. (6) Chemical control: Before yams are seeded, use 3% of Milor granules 3~5kg per 667m2, or 10kg of rayon granules 1.5kg of finely ground 30kg to spread in the planting ditch. Hook it up, about 10cm in depth, mix well with the soil, then carry out ditching and seeding. (7) Biological control: The use of bio-pesticide Beinian edodin EC to control root-knot nematode disease. Its usage is: before planting, every 667m2 is planted with 1.8% Beinong Aifuding EC 450~500ml mixed with 20~25kg fine sandy soil, evenly spreading the surface, then deep plowing 10cm, prevention and control of more than 90%, effective period of about 60d, or With Green Hunter Avi prevention.
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