In recent years, watermelons have been planted in the greenhouses of good crops field in Ji’an City, which has achieved good economic and social benefits. The output of 667m2 can reach more than 5000kg and the output value reaches 10,000 yuan; the watermelon rinds with gifts are thin and thick and soluble. Many things, sugar content as high as 14%, deeply loved by growers and consumers. However, due to the increasing cultivation area of ​​watermelons for gifts, and the repeated planting of the watermelons, the occurrence of wilt disease in watermelon is widespread and the damage is serious, resulting in a large area of ​​watermelon production. Therefore, only the prevention and control of watermelon wilt disease, greenhouse gifts can only guarantee the production of watermelon.
1 Symptoms
Watermelon wilt disease is also called vine disease and wilting disease. The onset of the seedlings showed that the leaves were wilting and drooping, and the bases of the stems browned and contracted and finally died. In the early stage of the disease, the watermelons in the shed appeared one after another. The symptoms showed that the leaves gradually wilted from the bottom to the top, appearing to be water-deficient, especially under the hot sun at noon, returning to normal at night or the following morning or cloudy days, lasting 3 to 6 days. The entire leaf wilted, no longer returning to normal. In later stages of the diseased plant, the epidermis of the base of the stem ruptured and a longitudinal crack appeared on the vine. Some roots of the diseased plant turned brown and rotted into hemp. In wet conditions, a small amount of white to pink mold layer, or sulphur brown to purple gum is produced on the surface of the diseased area. Shrimp disease examination showed that the vascular bundle was yellow-brown.
2 The law of occurrence
The pathogen of watermelon wilt is Fusarium oxysporum, a fungus belonging to the subphylum Aspergillus spp., which lives in the soil with mycelium, chlamydospore, or sclerotium, and survives in the soil. year. Soil carriers are the main source of infection, and seed carriers are the secondary sources of infection. The pathogens mainly invade through root wounds and root hair growth points, develop in the catheter, secrete toxins, destroy cells, block catheters, interfere with the transportation of water nutrients, and cause plants to wilt and die. The bacteria can grow at 4~38°C, and the most suitable temperature is 28°C. The germination temperature of spores is 24~32°C, and the soil temperature is 25~30°C. Soil acidity (pH: 4.2~6.0) and heavy soil mass are more serious; in the case of watermelon, the weather is persistently heavy, such as persistent rain, lack of sunshine, etc.; management is extensive, partial nitrogen fertilizer is applied, phosphorus and potassium fertilizer are insufficient, etc. Easily induced disease epidemics; heavy crop continuous cropping, heavy underground pest damage, low-lying terrain, poor drainage, waterlogging after rain, plant roots dysplasia, heavy root disease incidence.
3 Comprehensive prevention
In the greenhouse, the gift watermelon is grown. Because the temperature and humidity in the greenhouse are suitable for spore germination, and the weight of the soil in the greenhouse increases year after year, the occurrence of the wilt disease is also serious every year, forming continuous cropping obstacles. Therefore, the blight of the watermelon of the gift must be comprehensively controlled due to time and place.
3.1 seed disinfection
In order to reduce seed colonization, disease-resistant varieties, disease-free seeds should be selected, or harvested from disease-free plants. The seeds purchased should be seed-sterilized. Seed preparations should be soaked in 500-fold solution of 25% carbendazim for 1 hour, then rinsed out with clean water and germinated.
3.2 Soil disinfection
Before sowing or planting, use 25% carbendazim WP 500 times solution or 50% carbendazim WP 1000 times, or you can make it into the sowing pot or planting hole. 667m2 with 50% thiophanate-methyl 1.25kg or 50% carbendazim 0.75kg, first according to 1 part of the powder and 100% fine dry mixed soil, and then spread in the planting hole. After the watermelon seeds are collected in the spring garden, the soil shall be disinfected with lime nitrogen (calcium cyanide nitride) in combination with soil tillage, base fertilizer use, and high-temperature stuffy shed disinfection. It should be carried out more than 20 days before sowing and planting. Generally, after the application of manure fertilizer and other organic fertilizers, 667m2 is applied to 30-50kg of lime nitrogen, then the soil is deeply ploughed, the irrigation water is kept more than 70% of the soil moisture content, and the surface is covered with a film, the temperature of the closed greenhouse is increased, and the temperature of the 10cm can reach 50 in the greenhouse. Above °C, it is very beneficial to kill soil bacteria. After about 10 days, the disinfection is completed. Then, the membrane is ventilated and ventilated, the soil is ploughed, and the soil can be sown and planted over 7 days. The cyanogenic amines produced by the decomposition of lime nitrogen in China Agriculture Network are harmful to the human body. Special attention should be paid to safety protection when using it, and avoid mixing with acidic fertilizers such as superphosphate. The application of lime nitrogen soil disinfection can also prevent underground pests and other soil-borne diseases, supplement nitrogen and calcium fertilizers, promote the decomposing of organic matter, and improve soil structure.
3.3 Liquid Irrigation
2 days before colonization, 50% thiophanate-methyl 500-fold solution should be sprayed once on the colonization seedlings, or 50% carbendazim 1500-fold solution should be used as rooting water for rooting. At the beginning of the onset, 50% thiophanate-methyl 400-fold, agricultural anti-120 bactericide 10000-fold, 50% carbendazim 500-fold, or 40%-bouterin 600-fold can be used to irrigate the roots every 7-10 days. After reperfusion for one time, 250 ml of medicine was irrigated at each time. If the disease is severe, the combination of irrigation and rooting can be used to prevent 3-5 times.
3.4 Smoke
During the period of squashing, especially during the continuous rainy weather in late April, 45% chlorothalonil smoke agent or 15% procymidone 250g/667m2 was used for fumigation control.
3.5 Doing Comprehensive Agricultural Prevention and Treatment
First, the greenhouse management needs to strengthen ventilation and reduce the humidity in the greenhouse. The second is that the sick leaves and branches are cleared and burned outside the park in a timely manner. Third, organic fertilizer must be familiar with. Promote rotation for crop rotation, preferably with rice or aquatic vegetables for 1 year, with good control effect.
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