Occurrence and Control of Common Diseases of Watermelon

The common diseases of watermelon are: blight, anthracnose, blight, and viral disease, which seriously affect the yield and quality of watermelon. Now the hazards and prevention methods are introduced as follows:

I. Fusarium wilt

1, damage symptoms. Seedlings suffer from damage that can not be excavated and rot, or the emergence of cotyledons after the emergence of wilt, true yellow leaves, stems shrink browning and tripping. The diseased plants grow slowly and grow slowly. The yellow leaves of the lower leaves gradually develop upwards. At the new onset, the temperature rises at noon from the lower leaves and appears to be dehydration-like wilt. It gradually recovers in the evening and shows sluggishness at noon the next day and gradually develops to the upper part. . So repeated, the whole plant withered after a few days. In addition, only one or two of the vines withered after the plants were wilted, and the rest of the vines were normal. The epidermis of the diseased vine was rough and split longitudinally, and the vascular bundle turned yellow-brown to dark brown. When the disease was wet, pinkish moldy gums appeared in the diseased part.

2. Incidence conditions. The germs mainly come from the soil and the body of the disease, generally survive in the soil for 5-10 years, and invade from the wound or root canal of the root system. Seedling temperature 16-18 °C, 24-32 °C growth period is conducive to disease. In the flowering and fruiting period, in the event of high temperature and high humidity, the disease is severe, especially after long drought or heavy rain after long rain, the disease can easily occur seriously. In addition, the application of unfamiliar farmyard manure, low-lying water in the field, heavy clay soil, excessive watering, repeated cropping, and partial application of nitrogen fertilizer are also beneficial.

3, control methods. (1) Selection of disease-resistant varieties. For example, Zheng Zao No. 7, Xi Nong No. 8, Feng Kang No. 8, Hua Mi No. 8 and Hua Mi No Seed No. 3. (2) Seed soaking. Seed treatment with chlorothalonil, carbendazim, and acetic acid and other agents. (3) Agricultural control. Since this pathogen survives in the soil for many years, it is necessary to implement a rotation with non-guat crops, generally 6-8 years in dry land, and paddy fields in 3-5 years. Cultivation of sorghum and plastic film, watermelon planting, timely cultivation of loose soil, promote root growth. After the rain, drain the water in time to reduce the humidity in the field. The application of organic fertilizer, control the amount of nitrogen fertilizer application, appropriate application of phosphorus, potassium fertilizer and trace elements. (4) Chemical control. It should be prevention. Medicinal watermelon tannins and 40% melon humulus have better efficacy. The specific method is: After the watermelon is planted, combined with pouring root water, 50 grams of watermelon weighting agent is used for 30-40 kg of water, 0.2 kg of liquid per plant is used for irrigating or removing the sprayer nozzle, facing the stem, leaf and stem of the plant. Base spraying. When the bottom leaves of the diseased plants are wilting, use 40% guagunin 50 grams of water to 30-40 kg and 0.5 kg of liquid per strain to irrigate the roots. Before filling the roots, place a small bowl of cavities in the base of the stem of the diseased plants. Then the liquid was poured into it, in order to facilitate the resurrection of the diseased plants, temporarily sealed soil, let the sun shine according to the base, to be completely restored after sealing the soil, and then once again 7-10 days.

Second, virus disease

1, symptoms. The watermelon virus disease is caused by mosaic virus infection, and the diseased plants show systematic mosaic symptoms. In the early stage, yellow and green spots appeared in the leaves of the roots, and pale leaves and green leaves appeared on the top leaves, and the diseased leaves became small, ie, lobular, or shrinking deformed. Mild disease strains are still able to produce melons, but the melons are small. When the disease is heavy, little or no melons are formed. The plants shrink, the stems become shorter, the new stems are finely distorted, and the flower growth is poor. It is difficult to set melons.

2, the law of occurrence. Watermelon virus disease is caused by viruses and is transmitted through contact with media locusts and sap under high temperature and strong sunlight. Poor land, plant shortage of fertilizer, extensive management, growth weak water shortage of the land is prone to this disease. Viral disease occurs mainly in summer, that is, in the late growth period of spring watermelon. The incidence of watermelon in open field is more important than that of mulching watermelon, and the occurrence of mulching watermelon is more important than watermelon in greenhouse.

3, control methods. The seeds were selected from disease-free melons and soaked with 10% trisodium phosphate for 10 minutes, or the seeds were subjected to dry heat treatment at a constant temperature of 70°C for 72 hours. Focus on raising seedlings or laying silver ash on the fields to avoid scurrels. Watering in time when the weather is dry, and at the same time spraying 1000 mg/kg of drought-repellent agent No.1 on the watermelon enlargement period, about 50 kg of liquid per mu, which can promote watermelon enlargement, increase sugar content, control water consumption, and improve plant drought resistance and disease resistance . 400 meters around the watermelon field is best not to grow melon crops. The timely control of grasshoppers in the field can be achieved with 20% chrysanthemum cream 2000 times or 10% imidacloprid 2000 times. At the beginning of onset, 20% of virus A WP 500 times or 1.5% of phytolchnesis 800 times was sprayed, and once every 10 days or so, it was sprayed 2-3 times. If more multi-element fertilizers such as 999, Luyuan, etc. are added during spraying, the control effect will be better.

Third, anthrax

1, symptoms of the disease. The seedling stage shows stem curling, turning dark brown and easily causing cataplexy. At first, it was a small yellow water spot, which gradually expanded to black. The diseased part was dry, easily broken and perforated, and the leaves withered to death. The fruit stalk is sick, the young fruit is dark and atrophy leads to death. The mature fruit is affected. The diseased part begins with a water-stained ring, and afterwards, it appears as a dark depression. The upper part of the ring is arranged in black spots. When the disease is wet, the disease is covered. There are pink viscous conidia, which often cause secondary infections in the depression, causing the core to decay.

2, the cause of the disease. Pathogens are hairy spores and genus fungi. Bacteria attached to the victim tissue or soil, seed winter, the second year by wind and rain, humidity is a major factor in the disease induced. When the temperature is suitable and the relative humidity of air reaches 85-95%, the incubation period of bacteria is only 3 days. When the relative humidity is lower than 55%, the disease is not easy to occur. The temperature can be in the range of 10-30°C. The optimum condition is 20-25 °C, the greater the humidity, the more severe the disease.

3, control methods. (1) Selection of disease-resistant varieties or seed disinfection. After soaking in warm water of 55°C for 15 minutes, cool, or soaking for 30 minutes with 200 % 4% formalin, wash and germinate. (2) Fitness cultivation, proper close planting, timely pruning, ventilation and light transmission; appropriate application of phosphorus, potassium fertilizer, pay attention to drainage after the rain flood control, timely removal of diseased diseased leaves, the fruit with a straw pad. (3) According to the annual incidence period of 3-5 days in advance of spraying control, can be used 50% carbendazim WP, 70% thiophanate powder 1000-1500 times spray, spray every 7-10 days, continuous 3-4 times.

Four, blight

1, symptoms. Sprinkling disease can occur in all parts of the ground during the whole growth period of watermelon. The cotyledon of the seedlings was attacked by water-stained dots first, followed by brown sores and small round spots. As the disease progressed, the lesions expanded and merged with each other, eventually causing the cotyledons to die. Seedlings in the seedlings suffered from small lesions that initially appeared as water-stained spots, and then quickly expanded upwards and downwards. When the lesions surrounded the whole stalk for 1 week, the seedlings were withered and died due to interruption of nutrient transport. After the leaves were damaged, brown water-stained spots first appeared, and then expanded into irregular black-brown spots. In sunny and dry weather, there were obvious ring veins on the spots, and the ring lines were not obvious under high humidity conditions. In severe cases, lesions can spread to the entire leaf, causing the leaves to darken and die. Vine stem damage occurs at the base of the branch and the vicinity of the section, the initial short-spotted brown pits, expanded around the whole stem, the disease flow plastic, shrinkage, causing diseased parts of the melons withered.

2, the incidence of law. The bacterial pathogens of the blight disease mainly reside in the soil and mycelium or conidia overwinter on the seeds. After the emergence of the watermelons in the following spring, they encounter suitable conditions, causing initial infection, and later in the disease department. The conidiospore and conidia were produced and transmitted through rain and wind, and repeated infections were repeated. As a result, field diseases continued to expand and spread. In disease-free areas, transmission mainly depends on seeds. Because germs can not only survive on the seed surface, but also within the species can lurk bacteria. And can survive for about 2 years. The occurrence and spread of the disease has a close relationship with temperature and humidity. The bacteria can grow in the range of 5-35°C, more suitable for 20-30°C, especially 24-28°C. In the middle and early May, the watermelon stretches, in case of rainy days, rainfall. Large, high-humidity environments have not only rapid onset of bacterial blast, but also serious damage. The severity of the disease is closely related to continuous cropping. It was found during the survey that the cultivation of watermelons in successive years could aggravate the disease due to the accumulation of pathogens in the soil. Partial application and re-application of nitrogen fertilizer can cause stem vine growth and reduce disease resistance, thus aggravating the incidence and damage.

3, control methods. (1) Selection of disease-resistant varieties. (2) deep ditch squat, anti-scratch protection. Should choose the terrain Gaozao, well-drained field cultivation. At the same time, Guatemala should adopt sorghum cultivation in order to facilitate wet down. After each heavy rain, it is necessary to clean up the ditch once, so that the ditch is deeper than the ditch, and the ditch outside the ditch is deeper than the inner ditch. The bright water is discharged quickly and the dark water is filtered out. To ensure that the surface is free of stains, resulting in an environment that is not conducive to the occurrence of diseases and has a significant effect on the prevention and treatment of the disease. (3) Chemical control. Medications to prevent early medication, timely medication. When the center of the disease appears in the field, it should be sprayed immediately. Effective agents for the control of bacterial blight: 50% fast-king 1500 times; 50% haihai 1500 times; 80% "402" 3000 times. In addition, when transplanting seedlings and transplanting, with 10% double-effect Ling Shui agent 400 times watering planting points, each hole pouring diluted liquid 500 grams, not only can effectively control the blight, but also cure blight.

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