The cucumber in the greenhouse is often affected by low temperature during the winter or early spring cultivation. When the cucumber meets the continuous low temperature below its fertility temperature, it will cause physiological obstacles, prolong the growth period of the cucumber and reduce the yield, and when serious, it will develop into Freezing damage.
First, the symptoms
First, after sowing, the temperature is encountered, the ground temperature is too low, the seed germination will be delayed, resulting in weak seedling yellow seedlings, seedling emergence or damping-off, root rot disease, etc.; sometimes the edge of the seedling cotyledon appearing unearthed white edge, leaves yellow Although the root system is not rotten, it does not grow. If the ground temperature is lower than 12°C for a long time, the root tip turns yellow or roots appear, and the rotting phenomenon occurs, and the ground begins to turn yellow. Second, when the temperature during the day is between 20°C and 25°C for more than 6.5 hours and the nighttime temperature drops to about 12°C, the cucumber will have the phenomenon of slow seedling growth, seedling emergence, pale leaf color and yellowish leaf margin; when the night temperature Below 5°C, the growth is stagnant, causing the wilting of the seedlings, the yellowing of the leaf margins, and the small and small fruit size. When the low temperature of 0°C-5°C lasts for a long time, it will develop damage, and some will not develop rooting or flower buds. Differentiation is affected or does not differentiate, leaf tissue has not yet necrosis: but yellow, reduced resistance to disease, resulting in weak parasite infection, and some can induce sclerotinia, gray mold and other low-temperature diseases.
Second, prevention and control measures
1. Variety selection. Production should be fast-growing varieties with fast germination, rapid emergence, and fast seedling growth. For example, Zhongnong 7, Jinchun 3, Nongda 12th, Changchun Mickey and Beijing Spur were all resistant to low temperature, low light and early maturing.
2. Apply vernalization method. The seeds that are quickly germinated after being blistered are placed at a temperature of 0°C and frozen for 24-36 hours. After sowing, they not only germinate quickly, but also enhance the cold resistance.
3. Insulation measures. When the seeds germinate after cucumber sowing, the shelf temperature should be maintained at 25 °C ~ 30 °C. Most of the seeds can't germinate when the greenhouse temperature is lower than 12°C. Even if germination occurs, the emergence time is as long as more than 50 days. After emergence, the temperature should be kept at 25°C during the day, the night temperature should be higher than 15°C, and the soil water content should reach 80% of the maximum water holding capacity. Shed film should be selected without drip film and covered with drape; promote the use of mulch, small film, large film and other multiple coverage. Do not ventilate in the early period, timely in the medium term, moderate release of air. In case of cold currents, warming and antifreeze measures should be used immediately. Simple stoves or firewood can be used to ignite the firewood in the ridge to increase the temperature of the canopy by 3°C to 15°C. It should be kept for 2 to 3 hours. Ground covers or plants can also be used. Cover newspapers and mulches. When the outside temperature reaches 17°C, it is necessary to remove the film for cryogenic exercise earlier. Before the removal of the film, it is necessary to strengthen the night hardening of the 4～5. As long as it is sunny, the film should be gradually opened from small to large at night.
4. Increase carbon dioxide. Put a pot in a shed, slowly pour 50% of sulfuric acid 1000 ml into 3 pots. Then put 400 g of ammonium bicarbonate in a plastic bag and put some small eyes with a needle or a nail; let it flow into the pot. Sulfuric acid solution, the chemical reaction, the release of carbon dioxide, released at 7 am to 9 am, can make cucumber photosynthesis and increase resistance.
5. Drug treatment. Before the cold, 72% of agricultural streptomycin wettable powder 4000 times or 27% high fat film emulsion 80-100 times or plant cold resistant agent 100-200 ml/mu can be sprayed. All have certain preventive effects.
6. Remedial measures. If the temperature is too low and freezing damage has occurred, measures should be taken to increase the temperature slowly. After the sunrise, use newspapers or straw curtains to block the cucumber's physiological function and avoid rushing. (Anxin County Bureau of Agriculture and Forestry 071600)
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