Prevention and treatment of nine main diseases of watermelon

First, blight. Watermelon blight is a devastating disease of soil fax bacteria, which many farmers call "cancer" of watermelon. It is distributed throughout China. The incidence rate is generally about 5%, and the heavy ones are more than 30%, which is seriously damaged or even rejected. Watermelon can develop in the whole growth period, and the most serious disease is caused by vines. At the seedling stage, the base of the young stems became brown and contracted, and the cotyledons and young leaves wilted and drooped. In adult plants, the growth of the diseased plants is slow, and the lower leaves are yellow and gradually develop upward. In the early stage of the disease, the daytime wilting, recovery in the morning and evening, and the whole plant wilted after a few days. The basal part of the stem of the withered plant is rough and the roots are longitudinally split. When wet, the stem is water-soaked and rotted, and white to pink mildew, that is, the pathogen of the pathogen and the branching bun. The diseased part often flows out of the gel, and the stem vascular bundle turns brown. The roots of the diseased plants become partially dark or rot, and are easily pulled up. Control method: use resistant varieties. Seed treatment with chlorothalonil, carbendazim, naphthalene acetic acid and the like. It is used for rotation with non-melon crops, generally 6 to 8 years in dry land and 3 to 5 years in paddy fields. Sorghum and mulching cultivation, after planting watermelon, timely cultivating loose soil to promote root growth. After the rain, clear the ditch and drain the water in time to reduce the humidity in the field. Application of decomposed organic fertilizer, control of the amount of nitrogen fertilizer applied, appropriate application of phosphorus, potassium fertilizer and trace elements. The prevention and treatment of pesticides should be based on prevention, and the use of watermelon heavy tincture and 40% melon-sweeting is better. The specific method is as follows: after the watermelon is planted, combined with the root water, 50 g of watermelon heavy sputum is used for 30-40 kg of water, and 0.2 kg of liquid per plant is used to irrigate or remove the sprayer nozzle, facing the stems and stems of the plant. Base spray. When the bottom leaves of the diseased plant are wilted, 40% of the cucurbitin is used, 50 grams of water is 30-40 kilograms, 0.5 kilograms of liquid per plant is irrigated, and the base of the stem of the diseased plant is smashed into a small bowl-shaped hole. Then, the liquid is poured into it. In order to facilitate the resurrection of the diseased plant, the soil will not be sealed, and the sun will be exposed to the base. After the restoration, the soil will be sealed and then poured again 7 to 10 days later.

Second, anthrax. Anthracnose is one of the main diseases of watermelon. It is widely distributed, and the occurrence of protected areas and open fields is heavier. The general incidence rate is 20% to 40%, and the rate of serious block disease plants can reach 100%. In addition to the damage during the growth period, it can continue to be harmed during the storage and transportation period, resulting in a large number of rotten melons. The whole growth period of watermelon can occur, but it occurs most seriously in the middle and late stages of plant growth. It is mainly harmful to the leaves, but also can damage the stems, petioles and fruits. The seedlings are damaged, and round or semi-circular brown or dark brown lesions appear on the edge of the cotyledons. There are often dark brown halos around the leaves, and the spots are often scattered with black small spots or reddish sticky spots. The stem near the ground is damaged, and the base of the stem becomes dark brown, and the contracture becomes fine and collapses. Melon or petiole infected, initially water-soaked yellow-brown oblong spots, slightly sunken, dark brown after the disease, the lesions around the stem for a week, the whole plant died. The leaves are infected, initially round or irregularly shaped with water-stained spots, sometimes with wheel marks, and the spots are easily broken and perforated when dry. A pink viscous substance is formed on the lesions when wet. The fruit is infected, and it is initially a water-soaked concave brown round spot or long round spot, which is multi-cracked. When the humidity is high, a pink sticky substance is formed on the spot. Control methods: use disease-resistant varieties, do a good job of seed disinfection, and carry out rotation for more than 3 years with non-melon crops. Properly planted, pruned in time, ventilated and transparent. Appropriately increase the application of phosphorus and potassium fertilizers, pay attention to drainage and flood control after rain, and promptly remove the diseased plant leaves, and the fruits are padded with grass. Spraying according to the annual onset period of 3 to 5 days in advance, can be sprayed with 50% carbendazim WP, 70% methyl thiophanate powder 1000-1500 times, spray once every 7 to 10 days, continuous 3 ~4 times.

Third, the virus disease. The watermelon virus disease is caused by mosaic virus infection, and the diseased plant is a systemic mosaic symptom. The early root leaves showed yellow-green spots, and the top leaves showed pale green leaves, and the diseased leaves became smaller or wrinkled and deformed. The mild disease strain can still bear the melon, but the melon is small. When the disease is heavy, the melon is less or not melon, the plant is atrophied, the stem becomes short, the new stem is slender and twisted, and the flower is poorly developed, which is difficult to seat. Viral diseases mainly occur in the summer, that is, the growth of spring watermelon in the middle and late stages. The onset of watermelon in the open field is heavier than the watermelon in the mulch, and the incidence of the watermelon is more important than that in the greenhouse. Control method: the seed is selected from the disease-free melon, and soaked with 10% trisodium phosphate for 10 minutes, or the seed is subjected to dry heat treatment, that is, constant temperature treatment at 70 ° C for 72 hours. Concentrate on nursery or smear in the field. Watering in time when the weather is dry, spraying 1000 mg/kg of drought-resistant agent No.1 in the expansion period of watermelon, about 50 kilograms of liquid per acre, can promote watermelon expansion, increase sugar, control water consumption, and improve drought resistance and disease resistance of plants. . It is best not to plant melon crops around 400 meters around the watermelon field. In the field to control aphids in time, you can choose 40% omethoate 1000 times solution or 20% chrysanthemum EC 2000 times solution or 10% imidacloprid 2000 times solution. At the beginning of the disease, spray 20% virus A wettable powder 500 times liquid or 1.5% phytopathogenic 800 times liquid, and control once every 10 days, even spray 2 to 3 times. If you add more than one micro-fertilizer such as Duo, Luyuan 999, etc. during spraying, the effect is better.

Fourth, the blight. Bacterial wilt is one of the most important diseases of watermelon. It occurs in watermelon planting areas in China. The rate of diseased plants is generally 15% to 25%, and in severe cases it is as high as 60% to 80%. When the disease is popular, it can cause a large number of deaths in the melon field. Rattan, reduced yield by more than 30%, seriously affecting the yield and quality of watermelon. Due to the large area of ​​watermelon and the small number of resistant varieties, the occurrence and damage of watermelon blight has been increasing year by year. The whole growth period of watermelon can be affected in the upper part of the growth period, mainly affecting the vines, leaves and fruits, causing the leaves and vines to die and the fruits to rot. The seedlings of the seedlings are damaged, firstly water-stained small spots, and then form brown sores-like small round spots. As the disease progresses, the lesions expand and merge with each other, eventually causing the cotyledons to die. The stems of the seedlings were damaged, and initially appeared as water-stained small spots, which then expanded up and down rapidly. When the lesions circled the whole stem for 1 week, the seedlings withered and died due to the interruption of nutrient transport. After the leaves are damaged, the brown water stains appear first, and then expand into irregular black brown spots. In the sunny and dry weather, there are obvious wheel marks on the lesions, and the wheel marks are not obvious under high humidity conditions. In severe cases, the lesion can spread to the whole leaf, causing the leaves to darken and die. The vine stem damage occurs mostly at the branches and nodes of the base. The initial stage is a short strip of brown plaque. After the enlargement, it surrounds the whole stem. The diseased part flows and shrinks, causing the vines to wilted above the diseased part. Control method: use resistant varieties. Deep ditch sorghum, anti-staining and anti-smashing. Drug control should be used early, and timely medication. When the center of the disease occurs in the field, spray immediately. The effective agents for controlling blight are: 50% quick-kling 1500 times solution, 50% p-hydantoin 1500 times solution, 80% "402" 3000 times solution, and the like. In addition, when transplanting seedlings, the planting hole is watered with 10% double-effect spirit water 400 times solution, and 500 grams of diluted liquid is poured into each hole, which can not only effectively control the blight, but also cure the wilt disease.

5. Sclerotinia sickness. Sclerotinia sclerotiorum can occur in plastic greenhouses, greenhouses and open fields, but it is more serious in plastic greenhouses and greenhouses. It can be infested from the seedling stage to the adult stage, mainly damaging the stems, leaves and fruits of watermelon. The base of the stem is infected, the primary water stains are spotted, and then spread into pale brown spots, causing soft rot or longitudinal cracking at the base of the stem. When the humidity is high, the diseased part is white flocculent mycelium, causing the diseased stem to die. The leaves are infected, and the leaves are gray-brown and wet-like. When the humidity is high, the spots are covered with white floc and the leaves are rotten. In the case of melon infection, water-soaked spots appear in the flower buds of the young melons. After expansion, they are wet and rot-like, and the melons are densely white-like flocculent mycelium. In the later stage, the rat fecal sclerotia appears. Control method: Rotation with grass crops for more than 2 years or water and drought rotation. The decomposed organic fertilizer is applied to the greenhouse or the field to prevent the unfertilized organic fertilizer with the diseased body and sclerotia from entering the melon field. Seed disinfection, soaking seeds with warm water at 50 ° C for 10 to 15 minutes can kill the sclerotia. Disinfect the soil: apply 2 kg of 40% pentachloronitrobenzene powder per acre before planting the watermelon; take the medicine and colonize, that is, spray 25% triazolone wettable powder 5000 times solution in the seedbed before planting. Strengthen cultivation management, remove disease, yellow and old leaves, improve ventilation and light transmission in the field, and reduce humidity in the shed. Apply more base fertilizer, increase the application of phosphorus and potassium fertilizer, prevent plant growth and enhance disease resistance. To avoid watering in rainy days, watering less in the early stage. The best time to control the drug is in the early flowering stage or when the central disease plant is just found. The medicament may be selected from 25% triazolone wettable powder 3000 times liquid or 50% procymidone wettable powder 1000 times liquid. In the future, depending on the condition, a 50% carbendazim WP 300-500 times solution or 70% thiophanate-methyl WP 800-1000 times solution may be sprayed every 7 to 10 days. The application site is focused on the old leaves and the surface of the plant.

Sixth, powdery mildew. Powdery mildew is commonly known as "white hair", which is a common disease in the middle and late stages of watermelon growth. It mainly invades the leaves and also damages stems and petioles. The fruits are generally harmless. In the initial stage, a small round powder spot is produced on the front side of the blade. When the condition is suitable, the powder spot rapidly expands into a piece, which is like a layer of white powder. When it is serious, the leaves are yellow and brittle, stop growing, but generally do not fall off. Control method: select resistant varieties, reasonably close planting, and adopt high sorghum deep ditch planting methods. Timely pruning and mulching, preventing leaf vines from being too dense, affecting ventilation and light transmission. Do not apply nitrogen fertilizer, increase the application of phosphorus and potassium fertilizer, and enhance the disease resistance of plants. The residue should be completely removed before or after harvesting, and the old diseased leaves should be removed frequently during the growing season to reduce the source of infection. Take dry and wet irrigation, pay attention to drainage after rain. Spraying 2 or 3 times of 50% sulfur suspending agent 300 times solution or sulfur powder in the early stage of growth can prevent the occurrence of powdery mildew; 15% powder rusting wettable powder 1000-1500 times liquid, or 40% Fuxing emulsifiable oil 5000~ 6000 times liquid, or 20% nitrile emulsifiable concentrate 1500 ~ 2000 times liquid spray, spray every 6 to 7 days, even spray 3 times. In order to avoid the resistance of the bacteria, the agents should be used interchangeably.

Seven, the disease. Watermelon blight, also known as Phytophthora disease, commonly known as dead cockroach, is a high-temperature and high-humidity soil-borne disease. All watermelon producing areas have occurred, and the damage has been increasing year by year. Seedlings and adult plants can be affected, which are harmful to leaves, stems and fruits. In the seedling stage, a round, water-soaked dark green lesion appeared on the cotyledon, and the center of the lesion gradually turned reddish brown, and the base was obviously collapsed near the ground until it collapsed. The disease of the leaves is initially dark green water-immersed nearly round lesions. When the humidity is high, the soft rot is boiled, and it is easily broken when dry. The base of the stem was damaged, and the dark green water-immersed lesions of the spin-shaped depression were produced, and the stems were spoiled, and all the above parts of the disease died. When the fruit is damaged, it is a round depression with dark green water-immersed lesions, which spread to the whole fruit soft rot, and the surface is densely hairy white hyphae. Control method: select resistant varieties and disinfect the seeds. Rotation with non-melon crops for more than 3 years. Clean the pastoral, cut off the source of the overwintering bacteria, and find that the diseased plants are removed in time, concentrated or buried. No unfertilized organic fertilizer with diseased bodies. Reasonable close planting, deep sorghum cultivation, timely drainage after rain, control of field humidity. Watermelon cultivated in the facility should be immersed in small water or drip irrigation under the membrane to save water and heat to reduce the humidity in the greenhouse. It is strictly forbidden to flood and string irrigation. In the early stage of the disease, the diseased part or the root should be sprayed in time. The commonly used agents are 58% toxic manganese-zinc wettable powder 500-800 times liquid, or 25% toxic mycelium (metalaxyl) wettable powder 500-800 times liquid. Or 40% ethyl aluminum phosphate (Phytophthora) wettable powder 200 ~ 250 times liquid, or 72% DuPont grams of wettable powder 800 ~ 1 000 times liquid, or 70% nail cream aluminum copper wettable powder 250 ~ 500 times Liquid can be, usually sprayed once every 7 to 10 days, depending on the condition, continuous spraying or rooting 3 to 6 times. When the condition is serious, it can be irrigated every 5 days, and the effect is better. The facility should be combined with air release after each application to reduce the humidity in the shed.

Eight, leaf blight. Watermelon leaf blight is a disease that damages the leaves of watermelon. It has gradually increased in recent years. In the middle and late stages of watermelon growth, especially in the rainy season or after heavy rain, it is often acute and rapid development, which makes the melon leaves change rapidly. Black scorch, loss of photosynthesis ability, seriously affecting the quality and yield of watermelon. Leaf blight mainly harms leaves and can also damage stems and fruits. The seedlings of the seedlings are damaged, mostly at the leaf edge. They are initially water-stained small spots, and then expanded into brown water-stained, round or semi-circular spots. Under high-humidity conditions, the whole cotyledons can be harmed and withered. True leaf damage occurs mostly in the leaf margin or between the veins. It is initially a water-stained small spot. It merges rapidly under high humidity and penetrates, causing the leaves to lose water and dryness. In high-temperature and dry weather, round brown spots with a diameter of 2 to 3 mm are formed. When the weather is wet, they can be merged into large brown spots. The lesions become thin and cause leaf dryness in severe cases. Stem vines are damaged, producing light brown spots with elliptical or fusiform, micro-depression. When the fruit is damaged, it produces a dark brown spot with a rounded depression around it. When it is serious, it causes the fruit to rot. Black mold can grow in all affected parts when wet. Control method: select resistant varieties and disinfect the seeds. After harvesting, the watermelon should be cleaned up in time, and the sick body should be burned or buried deeply. At the same time, the land should be turned over to reduce the source of bacteria. Heavy disease plots or sheds are rotated with non-cucumber vegetables. Formulated fertilization technology to avoid excessive application of excessive nitrogen fertilizer. Strengthen field management, avoid water accumulation in the field, increase ventilation after onset, and reduce field humidity. In the early stage of the disease, the drug can be controlled by using 70% thiophanate-methyl WP 600 times solution, or 40% polysulfur suspension 500 times solution, or 50% chlorhexidine WP 1500 times solution, or 40% Fuxing emulsifiable concentrate. 8000 times liquid spray.

Nine, cotton rot disease. Watermelon rot is the main disease of watermelon during the melon period, which is common. The entire growth period can occur. The onset of seedling stage caused the melon seedlings to collapse. In the case of melons, the main infringement of melons and fruits is that the disease occurs first in the vicinity of the ground. The initial diseased parts are brown and water-stained, and then quickly soft rot. When the humidity is high, the dense meticulous hyphae are formed in the disease minister; Rotten, smelling bad. Sometimes it also causes rottenness and death. Control method: cultivation with sorghum. Avoid flooding with large water, drain it in time after heavy rain, and pad the melon if necessary. In the early stage of the disease, spray 14% solution of lysine copper water solution, or 50% humic acid copper (DT) wettable powder 500 times, once every 10 days, continuous control 2 to 3 times.