Control methods of watermelon anthracnose

Watermelon anthracnose can occur in the whole growing period, but it is the most serious in the middle and later stages of plant growth, resulting in dead leaves and fruit rot. At the time of seedling disease, round brown disease spots appeared on the cotyledons, and the base of the young stem became dark brown, and constricted, even inverted. When the disease occurs in the adult stage, there are water-immersed round yellowish spots on the leaves, then turn brown, the edges are purplish brown, the middle is light brown, and there are concentric wheel patterns. The enlargement and fusion of disease spots can easily cause leaf perforation and dryness. On the immature fruit, the disease spot is flooded and light green in the early stage, and it begins to show protuberant disease spot on the mature fruit, then expands into brown depression in the later stage, and arranges many small black spots in a ring, and produces pink sticky matter when it is wet, which is deformed or blackened and rotten.

Harmful symptoms of watermelon anthracnose

Watermelon anthracnose mainly harms leaves, as well as stems, petioles and fruits. Round or semicircular brown or dark brown disease spots appeared on the edge of the injured cotyledons of seedlings, and there were often black-brown halos on the periphery, and small black particles or reddish sticky substances were often scattered on the disease spots. The stem near the ground was damaged, and the base of the stem turned dark brown and constricted and became fine and quenched. Melon vine or petiole infected, initially water-immersed yellowish brown oblong spots, slightly sunken, and then become dark brown, the disease spot around the stem for a week, the whole plant withered. When the leaves are infected, they are initially round or irregular water-stained spots, sometimes with wheel lines, and the disease spots are easy to be broken and perforated when dry. Pink sticky material is produced on the plaque when it is damp. At the beginning of the disease, the fruit is water-immersed sunken brown round spot or long round spot, often cracked, pink sticky substance is produced on the spot when the humidity is high.

Incidence regularity of watermelon anthracnose

Watermelon anthracnose is caused by a fungus of the genus Cephalosporium. The optimum temperature for the disease is 22 ℃ 27 ℃, and the plaque stops growing below 10 ℃ and above 30 ℃. The pathogen overwintered in the residual plant or soil, and the temperature and humidity were suitable in the second year. The overwintering pathogen produced spores and began to infect for the first time. Pathogens attached to seeds can directly invade cotyledons and cause seedling disease. Under suitable conditions, the pathogen will produce spore disk or conidia and infect again. Conidia are mainly transmitted by running water, wind and rain and people's production activities. When picking melons, if there are conidia on the fruit surface, the disease can also be infected in the process of storage and transportation. The occurrence of anthrax is closely related to humidity. Under the suitable temperature, the higher the relative humidity is, the more serious the disease is. When the relative humidity is 87%-95%, the incubation period of the bacteria is only three days. The lower the humidity is, the longer the incubation period is. When the relative humidity is below 54%, the disease will not occur. In addition, excessive use of nitrogen fertilizer, poor drainage, poor ventilation, excessive density, plant weakness and continuous cropping, the disease is serious.

Preventive measures of watermelon anthracnose

In the disease-prone period, "Sujing" 30ml was sprayed with water and 15kg, once every 7 days.

Agricultural control of watermelon anthracnose

The prevention and control of anthracnose of watermelon anthracnose should focus on selecting disease-resistant varieties, adjusting indoor humidity to below 70%, and paying attention to the protection of the whole growth period.

1. Select disease-resistant varieties: Qi Hong, Qilu, Kaiza No. 2, Kaiza No. 5, Jingxin and Xingmi.

2. Seed disinfection and cultivation of disease-free and strong seedlings.

3. Implement crop rotation, apply fertilizer reasonably, reduce the amount of nitrogen fertilizer, and increase the application of potash fertilizer and organic fertilizer.

4. The ground is fully covered with plastic film and ventilation should be strengthened to reduce the indoor air humidity to less than 70%.

5. Reasonable close planting and scientific pruning to prevent excessive density so as to reduce the humidity of indoor microclimate.

6. Scientific use of germicidal pesticides.

Treatment of watermelon anthracnose

1. "Sujing" 50ml + "garlic oil" 15-20ml mixed with water 15kg spray, 3murine once every 5 days, continuous use for 2-3 times, after the disease was controlled, it was transferred to the prevention scheme.

2. At the initial stage of the disease, 50% thiophanate wettable powder 800 times plus 56% azoxystrobin 800 times, or 50% carbendazim wettable powder 800 times plus 75% chlorothalonil 800 times mixed spray.

3. In addition, 38% carbendazim 800-fold solution, 36% thiophanate suspension 500-fold solution, 80% anthrax Fumei wettable powder 800-fold solution, 2% antimycin (pyrimidine nucleoside antibiotics) water agent 200 times, 2% Wuyisin water agent 150 times, once every 7 to 10 days, continuous prevention and control for 3 times.

4, or 20% fluorosilazolium 1000 times, 80% anthrax Fumei 800 times, or 25% difenoconazole water dispersible granules 1000 times. Spraying medicine once every 7 days, spraying 3-4 times successively, alternating in turn, the control effect is better.

5. 20% clotrimazole water emulsion 800 times has a special effect on anthrax.