Prevention and cure of watermelon blight

Bacterial blight of watermelon can be affected in the whole growth period. The leaves were affected, and most of them started from the cotyledons, and they initially showed brown water stains and small spots. They gradually developed into round or irregular brown spots with a diameter of 1-2 cm. There were ring veins on the lesions and the center color was light. The edge is dark brown and clearly demarcated with normal tissue, with many small black spots on it.

The damage to stems and vines starts from the stems of the seedlings and starts with water-spotted small spots. It quickly develops upwards and downwards and surrounds the young stems, causing death of the seedlings. The incidence of adult plants is more common in the branches or branches of the stem. Begins with watery lesions near the joints. The lesions are oblong or short, slightly sunken, and secrete amber-like olivary material (see figure). The lesions expand around the entire stem, followed by the diseased part. Shrinkage, the diseased part of the above part withered.

The fruit was affected. It initially appeared as a small spot with oily stains. It turned dark brown with round lesions. Its surface was chapped, and it was corked internally. It often had a star-shaped crack, with small dark spots on the lesions at the late stage, and finally caused the entire fruit to rot.

The severity of the disease is closely related to temperature, humidity and cultivation management techniques. In the range of 10°C-34°C, the incubation period of pathogenic bacteria was shortened as the temperature increased, and the relative humidity of air was more than 80% and it was easy to develop. Continuous cropping, low-lying terrain, accumulation of water after rain, lack of fertilizer or weak growth, disease development, excessive close planting, poor ventilation, and high humidity are prone to disease.

Prevention measures

1. Seed treatment. Seed treatment before sowing has better control effect on sp Specific operation methods: Before sowing, use 70% mancozeb WP 750 times or 50% thiophanate 500 times soaking for 1-2 hours, can effectively control the incidence of seedlings.

2. Agricultural control. The plots for planting watermelons are best used for 2-3 year rotations with non-guad crops; full base fertilizers are used to make organic fertilizers, especially cake-based fertilizers. Nitrogen, phosphorus, and potassium are used in combination. Do not apply nitrogen fertilizer to balance. Formula fertilization, enhance plant growth; choose a good irrigation and cultivation of land, timely removal of diseased leaves in the event of rain, after harvest completely clean up the residual diseased bodies and weeds in the ground, buried deep or burned to reduce the source of the disease. The planting method is to choose ditch planting or high ridge planting. If the land with heavy salinization can be planted in ridge and furrow, that is, open 80 cm wide and 20 cm deep, and make a width of 50 cm and a height of 10 cm at the bottom of the ditch. In the small ridges, water can flow from the stems of the seedlings when it is watered, reducing the salt content around them, and can avoid water accumulation around the shoots after watering. Practice has proved that this method can significantly reduce the incidence. In addition, cultivating grass under the melon vines can also effectively reduce the chance of pathogenic bacteria infection, and at the same time reduce the humidity, thereby reducing or preventing the occurrence of diseases.

3. Chemical control. Can be used 40% fluorosilicone EC 3000-5000 times solution + 65% Zexon WP wet 600 times; can also be used 10% difenoconazole water dispersible granules sprayed 1500 times, 7-10 days spray 1 time, even spray 2-3 times; for the heavier plants, first use a knife to scrape the rot tissue, and then use 70% thiophanate-methyl WP 50 times or 40% fluosilazole EC 100 times. The use of brush pen medicine spread stem lesions, can better control the occurrence of watermelon blight.

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