Vigilance against grey mold in shed

Gray mold of Chinese leeks is an important disease of leeks in protected areas. When the conditions are appropriate, cinerea cinerea appears only once in the day and night from the point of initial infestation to spotting, and it takes only 2 to 9 days from spotting to outbreak of the whole shed. Therefore, vegetable farmers must guard against the occurrence of grey mold of leeks.

First, the harm symptoms

Amaranth grey mold mainly damages the leaves, and the symptoms are white spot type, wet rot type and dry tip type. White point type: White or grayish-brown small spots appear on the front or back of the leaves, resulting in scorching of whole or half leaves. Wet rot type: during the growth period or storage and transportation period, when the humidity is too high, wet rot symptoms often appear, the diseased leaves do not produce white spots, but gradually rot and appear dark green, dead leaves surface dense gray to green villous mold, With musty taste. Especially during storage and transportation, the leeks are bundled into bundles, and the speed of mutual contamination and infection increases, causing bundles of leeks to rot into a pile of mud, causing serious economic losses. Dry-tip type: It rots at the cutting edge of the cutting knife, it is water-stained at the beginning, it turns light green, and it has a brown ring pattern. After the lesion has expanded, it has a “V” shape and can extend downwards by 2 to 3 cm. It is yellow-brown and has gray-brown or gray-green villous fungi on its surface.

Second, comprehensive prevention measures

1. Increase farm manure and phosphorus and potassium fertilizers. Since leeks produce sufficient nitrogen fertilizer to produce high yields, people often use large amounts of urea and ammonium nitrate. Practice has proved that a large number of single application of nitrogen fertilizer is also an important condition for the initiation of gray mold. Therefore, in the application of nitrogen fertilizer, phosphorus and potassium should be applied together. For example, 15 to 20 kg of diammonium per acre, 20 to 25 kg of potassium sulfate, and 10 to 15 cubic meters of rotten manure.

2. Control temperature and humidity. According to weather conditions, open a certain amount of greenhouse film at noon for ventilation cooling and dehumidification. Through the control of air release, the maximum temperature in the shed is no more than 25°C, the temperature difference between day and night does not exceed 10°C, and the relative humidity in the shed is controlled below 70%. Note that an apron should be added to the edge of the booth and it is forbidden to vent from the bottom.

3. Clean up old leaves. When harvesting leeks, they must take all the excised parts out of the shed, and then clean up the tying. For the cleaned sick leaves and old leaves, they must be buried deep.

4. The rotation is down. Severe disease fields should be rotated for 2 to 3 years with cruciferous, gourd, and other vegetables, not onion or garlic.

5. Strengthen insulation and prevent freezing damage. Botrytis cinerea is easily invaded by wounds. When the temperature in winter is lower than 0°C, after frostbite is produced, the botrytis cinerea is easily induced. Therefore, when the temperature of the shed approaches 0°C, a small plastic shed is temporarily buckled on the ridge to increase the temperature by 3°C to 5°C, which has a good antifreeze effect, which can reduce the occurrence of gray mold.

6. Drug control. First, spray control was performed after each harvest. It can be sprayed with 50% fasting WP 1200 times solution or 50% acetaminophen wettable powder 1000 times solution. Followed by the beginning of the disease, use 10% fast Ke Ling smoke agent or 45% chlorothalonil smoke agent smoke prevention and treatment, 250-300 grams of smoke agent per mu, 8 to 10 points, with dark smoke smoke 3 ~ 4 hours.