Measures for Coping with Greenhouse Vegetables During Hazy Weather

Recently, the continuous hazy weather in North China has caused weak light and low temperatures in vegetable greenhouses, becoming a key factor affecting vegetable growth. Many vegetables have shown problems such as yellow leaves, dried tips, rotten growing points, root rot, flower and fruit drop, and severe diseases. In response, protected cultivation vegetables should adopt the following measures for management.

1. Keep the existing vegetables in the greenhouse alive. During the day in the greenhouse, as long as the temperature reaches above 18°C, carry out short-term ventilation (about 20 minutes). When there is no dew on the leaves, spraying can be done, and silicone adjuvant should be added to improve pesticide absorption and utilization. Taking cucumber and tomato as examples, to control downy mildew, Phytophthora blight, and gray mold, spray 60% Baitai + 5% Zhongshengmycin + 72% agricultural streptomycin; every 2-3 days, use 5% chlorothalonil smoke agent or 10% procymidone smoke agent for closed fumigation at night to reduce the occurrence and development of diseases. For vegetables that need watering, do not water on cloudy days; foliar fertilizer can be sprayed to supplement nutrients, and watering can wait until sunny days. For cucumbers that have formed "flower topping," appropriate fruit thinning can be done; yellowed leaves should be removed and taken out of the greenhouse, and pesticides or fumigation should be applied in time to reduce disease aggravation caused by wounds from artificial leaf removal.

2. Management during continuous cloudy days and after sunny days. Continuous cloudy days exceeding 5-7 days can easily cause root rot. In some areas, hazy weather lasts more than half a month, and most vegetable roots show varying degrees of rusty roots, with almost no white roots capable of absorbing nutrients. If partly cloudy and partly sunny weather causes the temperature to gradually rise, the damage to seedlings is somewhat less; if it suddenly becomes sunny, corresponding measures must be taken. (1) When the temperature inside the shed rises to 23°C, begin ventilation. If leaves wilt, spray white sugar + vinegar (50 grams each) diluted 150 times, or spray foliar fertilizer plus white sugar on the leaves to increase air humidity and slow the wilting. When the temperature rises above 26°C and wilting occurs again, cover with straw mats again, covering 2/3 of the shed surface, and promptly roll up the straw mats after the seedlings return to normal. The next day, continue to observe the performance of the seedlings. If wilting still occurs, spray chlorothalonil + streptomycin + brassinolide to reduce disease occurrence and promote seedling rooting. (2) When the seedlings need watering, do not water first if it suddenly becomes sunny; when the 10 cm soil temperature rises back above 16°C, water lightly, and try to raise the soil temperature as much as possible. (3) Raise the soil temperature. After it becomes sunny, as long as the seedlings do not wilt, ventilate lightly in the morning at around 23°C. When the temperature drops by 1.5°C-2°C, close the vent. When it rises above 28°C, ventilate again. If after ventilating at 23°C in the sunny morning, the temperature only drops by 1°C-1.5°C and rises again quickly after a short time, the vent need not be closed, but when the midday temperature reaches 30°C, increase the ventilation volume. In the afternoon, when the temperature drops to 25°C, close the vent. If the temperature rises by 1°C-2°C, it is beneficial for raising the soil temperature and storing heat, which is conducive to root growth.

Wang Shujun, Agriculture and Animal Husbandry Bureau of Chengde County