What are the common diseases of cucumbers in cold frames? How to prevent and control them

AbstractDowny mildew: spray 25% metalaxyl 800x solution, once every 7-10 days, for about 3-6 days in a row. Fusarium wilt: use 50% thiophanate-methyl 400x solution, or 50% carbendazim 500x solution and other chemicals to drench the roots. Powdery mildew: spray 40% DuPont Fuxing 2000x solution. Bacterial angular leaf spot: spray 47% Kasugamycin-copper 600-800x solution. Phytophthora blight: spray 25% metalaxyl 800x solution.

I. Downy mildew

1. During the vigorous growth period of the plants, downy mildew is relatively easily triggered when the greenhouse temperature is too low, watering is excessive, the field is too densely shaded, or in rainy weather, with temperatures of 15-18°C and air humidity above 80%.

2. In the early stage of the disease, spray 64% Sandofan 400x solution or 25% metalaxyl 800x solution or 72.2% Previcur 800x solution, once every 7-10 days, for about 3-6 days in a row.

3. If the disease breaks out and cannot be controlled, the high-temperature greenhouse sealing method can be used when the plants are strong and healthy.

4. Choose a sunny morning to water, thereby increasing the indoor humidity and enhancing the plants' ability to tolerate high temperatures. Seal the greenhouse to raise the room temperature to about 45°C, start timing from 43°C, keep it for 1.5-2 hours, and then begin to cool down.

5. Sealing the greenhouse will affect the growth of the plants and young cucumbers; at this time, apply quick-acting fertilizer or foliar nitrogen solution to supplement the nutrients the plants need, so that they can return to normal growth as soon as possible.

II. Fusarium wilt

1. Conditions that make the disease relatively likely to occur include: heavy clay soil, excessive watering, poor drainage and irrigation conditions, many soil-borne pests, and more root damage; when the temperature is around 24-30°C, the disease spreads relatively quickly.

2. In the early stage of the disease, use 50% thiophanate-methyl 400x solution or 50% carbendazim 500x solution for root drenching, using about 250 grams of solution per plant, once every 10 days, for about 2-3 times in a row.

3. Severely affected plants must be pulled out immediately; to prevent the disease from spreading through flowing water and cultivation, apply chemicals into the planting holes of diseased plants.

4. To prevent pathogens from infecting plants through wounds, when carrying out pruning, cultivation, cucumber picking and spraying and other pesticide operations, the root system and stems and vines must not be damaged.

III. Powdery mildew

The disease is relatively likely to occur under conditions of excessive plant growth and densely shaded fields; in the early stage of the disease, spray Nongkang 120 or 40% DuPont Fuxing 2000x solution, once every 7-10 days, for about 3-4 times in a row.

IV. Bacterial angular leaf spot

Conditions prone to the disease: more rainfall, poor ventilation, relatively high field humidity, etc. In the early stage of the disease, spray DT bactericide 500x solution or 47% Kasugamycin-copper 600-800x solution, once every 5-7 days, for about 3-4 times in a row.

V. Phytophthora blight

Conditions prone to the disease: high temperature and rainy weather, relatively high field humidity, etc. In the early stage of the disease, spray 25% metalaxyl 800x solution or 72.2% Previcur 400-600x solution, once every 5-7 days, for about 3-4 times in a row.