Disease control measures of watermelon

The main diseases of watermelon are: watermelon anthracnose, watermelon quenching disease, watermelon virus disease, watermelon powdery mildew, watermelon blight, watermelon cotton rot, watermelon white silk disease, watermelon vine blight, watermelon brown rot, watermelon root knot nematode, watermelon leaf blight and watermelon wilt and so on.

1. Watermelon anthracnose

[symptoms] at the seedling stage, semicircular or round brown spots appeared at the edge of cotyledons, with black dots or reddish sticky matter. The young stem was damaged, and the diseased part was dark brown and constricted, causing melon seedlings to lodge. Leaf disease spot, in fact, is a round light yellow water stain-like spot, and then turn brown, the edge is purple-brown, the middle light brown, there are concentric wheel patterns and small black spots. Plaques are prone to perforation.

[occurrence regularity] the optimum temperature for the growth of the pathogen was 24 ℃-25 ℃, the humidity was more than 90%, and the disease was mild under the condition of high temperature and drought.

[control methods] first, disinfect the disease-free seeds or seeds, soak the seeds in 55 ℃ warm water for 15 minutes, or soak the seeds in 40% formaldehyde solution for 30 minutes, rinse with clean water and accelerate germination. At the initial stage of the disease, 70% mancozeb can be sprayed 400-500 times, 65% mancozeb or carbendazim 500 times, once in 5-6 days, 2-3 times in succession.

2. Watermelon quenching disease

[symptoms] at the beginning of the disease, the seedlings showed yellow water stains near the ground, then turned yellowish brown and dried up and contracted, and the seedlings were broken as soon as they were pulled out.

[occurrence regularity] germs spread with Rain Water and running water. Low ground temperature (10 ℃-15 ℃), high humidity of seedling bed, cool night and lack of light during the day are beneficial to the disease. There are more bacteria in seeds and beds, and there are more chances of seedlings being susceptible to disease.

[prevention and control methods]

① agricultural control. Strictly select the soil with high terrain, good drainage and unplanted melons. Strengthen the management of seedbed and do a good job of heat preservation, ventilation and humidity reduction. When the humidity of the seedbed is too high, a small amount of plant ash or dry soil can be sprinkled and ventilated to reduce humidity.

Chemical control of ②. Immediately pull out the diseased seedlings when the diseased plants appear, and spray the copper ammonia mixture to prevent the spread of the disease. It can also spray 75% chlorothalonil 700-800 times.

3. Watermelon virus disease

[symptoms] the upper leaves of muskmelon plants first showed symptoms, showing dark and light green flowers and leaves mottled, leaves becoming smaller and curly, stems twisted and atrophied, and plants dwarfed. Melons and fruits become smaller, and there are dark and light green mottles on them. Watermelon damage, the leaves appear yellow and green spots, uneven leaves, new leaf deformities; infected leaves narrow, wrinkled and twisted, floral organ dysplasia, no fruit or fruit deformity.

[occurrence regularity] High temperature and strong sunshine are beneficial to the disease, and the melon fields with lack of fertilizer and weak growth are often serious.

[control methods] to kill aphids in time, the effective agents are 3000 times of butyl emulsion, 2000-3000 times of deltamethrin and 1500-2000 times of dimethoate EC. In severe cases, spray 15 kg of water with 4 sticks of 800000 units of penicillin. Or the foliar effect of spraying 15 kg water with 2 antitoxin (20 ml) plus 50 grams of zinc sulfate is also significant.

4. Watermelon powdery mildew

[symptoms] at the beginning of the disease, small round white spots appeared on the leaves, and then expanded into white powder spots, which were connected into pieces, so that the leaves and stems were covered with white powder.

[occurrence regularity] when the field humidity was high and the temperature was 16 ℃-24 ℃, the disease was serious. Planting watermelons and melons in greenhouses and greenhouses is often due to poor air circulation and high humidity, which is earlier and more serious than that of open field cultivation.

[control methods] pay attention to field hygiene, remove diseased leaves in time and burn them centrally. Strengthen cultivation management, increase the application of phosphorus and potassium fertilizer, and improve plant resistance. The initial stage of the disease can be sprayed with agricultural antibiotic 120,200 times, or 15% pink rust 1500-2000 times, or 70% methyl topiramate wettable powder 800-1000 times.

5. Watermelon blight

[symptoms] both seedlings and adults can suffer from the disease, harming leaves, stems and fruits. Cotyledons infected with the disease first showed flooding dark green round spots, the center gradually became reddish brown, constricted or withered near the ground, true leaves infected, primary dark green water immersed round or irregular spots, rapid expansion, high humidity, rot or scalded like boiling water, light brown after drying, easy to break, the base of the stem infected, spindle-shaped immersed dark green sunken spots, surrounded the stem and rotted, all died above the affected part. When the fruit is infected, a dark green round water-immersed concave spot is formed, which rapidly extends to the whole fruit, causing the fruit to rot and emit the smell of silage.

[occurrence rule] the temperature limit of onset was 5 ℃-37 ℃. The optimum temperature was 20 ℃-30 ℃. The disease occurred rapidly in rainy season, high temperature and humidity, poor drainage, over-dense planting, dense stems and leaves or poor ventilation.

[prevention and treatment methods] at the initial stage of the disease, 50% nail cream copper wettable powder was sprayed 700-800 times, 35% ridozole copper wettable powder 800 times, 72.2% Pulic water 800 times, 58% Redomir-manganese zinc (Ruidu zinc) wettable powder.

6. Watermelon sheath rot

[symptom manifestation] the main harm to the fruit is caused by disease in seedling stage, quenching and melon setting stage. The watermelon affixed to the soil fell ill first, and the disease showed brown water immersion at the beginning, then softened quickly, resulting in the browning and soft rot of the whole watermelon.

[occurrence regularity] the average temperature is 22 ℃-28 ℃, and more overcast or rainy days or high humidity are beneficial to the occurrence and spread of the disease.

[prevention and control methods]

① uses antibiotics to inhibit pathogens. For example, spraying 600x solution of agent "5406" 3 in the melon field can rapidly increase the number of antibiotics in the soil, which can inhibit the growth of pathogenic bacteria and achieve the purpose of disease prevention.

② was cultivated in high border. Avoid flood irrigation, drain water in time after heavy rain, and cushion melons if necessary.

At the initial stage of ③, 14% copper complex ammonia solution was sprayed, or 50% copper succinate (DT) wettable powder was sprayed, once every 10 days, for 2-3 consecutive times.

7. White silk disease of watermelon

[symptoms] the injured part showed dark green plaque at first, then enlarged and slightly sunken.