Cucumber is a common vegetable in life, and it is loved by people because of its good taste, delicious taste and rich nutrition. However, during the growth of cucumber, some pests and diseases will occur. Today, Xiaobian will tell you about the occurrence and prevention of cucumber yellow leaf disease.
Causes of cucumber yellow leaf disease
First, the yellow root of the wound
The yellow leaf caused by poor root or root injury is the most important cause of the current yellow leaf of cucumber. This yellow leaf is mainly caused by excessive rooting of watering and fertilization, or caused by roots caused by continuous cloudy days after watering. Its symptoms are: the leaves of the plants are generally yellow, especially the top leaves are small, the growth is slow, and the stagnation occurs in severe cases.
In this regard, it is recommended to combine sprinkler irrigation and comprehensive prevention. Spraying, that is, foliar application of zinc and iron-containing foliar fertilizer and then mixing cytokinin 600 times solution to prevent leaf senescence and promote leaf greening. Irrigation, that is, applying rooting seedlings or chitin to promote root growth.
Second, the lack of yellow leaves
The ground temperature is low, the root activity is poor, and the nutrients absorbed by the roots are insufficient to meet the growth requirements of cucumber plants and fruits, thus causing cucumber yellow leaves. Especially after the root injury, it is more likely to cause the occurrence of symptoms of deficiency, which in turn increases the occurrence of yellow leaves.
The yellow leaf of the deficiency type is divided into two cases: the middle yellow and the middle yellow, and the middle and upper leaves. The middle and lower parts of the old yellow leaves are mostly nitrogen and potassium; the middle and upper leaves are yellow, and the missing elements are mostly calcium, iron and zinc.
In this regard, it is recommended that the correct leaf fertilizer should be selected for spray supplementation according to the different parts and different manifestations of the yellow leaf disease. For example, potassium deficiency can be sprayed with potassium dihydrogen phosphate 500 times solution, nitrogen deficiency can be sprayed 300 times of urea solution, calcium deficiency can be sprayed with 1000 times solution of green Fenwei 2 and so on.
Third, the disease yellow leaves
Downy mildew, angular spot, brown spot, and viral diseases are all important causes of cucumber yellow leaves. Downy mildew and angular spot disease are mostly harmful to the middle and lower leaves of cucumber. Brown spot disease has been on the rise in recent years, and it has started from the central leaves and developed rapidly. The vegetable farmers are commonly known as “small yellow spotsâ€. Although the greenhouse environment is low-temperature and high-humidity recently, the viral disease is still serious, and its symptoms occur mostly on the leaves of the cucumber growth point, causing yellow-green mottled mosaics.
For the diseased yellow leaves, the fungicide should be applied in time for prevention and treatment. Can use Plex 600 times solution plus DT500 times solution plus white sugar 300 times solution to prevent downy mildew and bacterial angular leaf spot; can be used with methyl thiophanate 700 times liquid plus Baitai 1000 times liquid and then mixed with aromatic leaf fertilizer 500 Double liquid spray to prevent brown spot disease; 300 times of Ningnanmycin can be mixed with zinc leaf fertilizer and Yunda 120 spray to prevent viral diseases.
Fourth, the drug damage yellow leaves
When farmers use medicine to prevent disease, the dosage is generally too large. However, in winter, the vegetables grow slowly, the growth is relatively weak, and the resistance is also weakened. The one-time overdose is easy to produce yellow spots. If the spray of mancozeb is excessive, it is prone to manganese poisoning, resulting in yellowing of the leaves and distortion of the veins.
In this regard, it is recommended that the pharmacy must be reasonable. Once the phytotoxicity occurs, the foliar spray can be used to relieve the pollution of the 6000 times liquid and the 600 times liquid.
Five, bad weather, yellow leaves
In winter, there are many cloudy days, and the shed time is short. The weak light and gas damage can also cause cucumber yellow leaves. In the winter greenhouse management, it is necessary to uncover the grasshoppers, release the wind, ventilate the light and eliminate the harmful gases, and cooperate with the foliar application of chitin to add the whole nutrient leaf fertilizer to protect the leaves and improve the resistance of the leaves.
Cucumber yellow leaf disease prevention and treatment method
1. Nitrogen-deficient yellow leaves. The growth of the whole plant was inhibited, the leaves were small, and the upper leaves were smaller; gradually turned yellow from the bottom to the top; the veins were prominent, and then extended to the whole leaves; the fruit was small and the swelling was slow. Control method: 5-10 kg of urea per acre, and spray 0.5%-1% urea solution 2-3 times on the foliar surface.
2. Potassium deficiency yellow leaves. There was no obvious inhibition on plant growth, and the leaf margin was slightly yellow in the early growth stage, and then spread to the veins. In the middle and late growth stages, the leaf margin was chlorotic and even necrotic. Sometimes there were chlorotic to necrotic spots on the leaves; the melon strips were short and the swelling was poor. Control method: 5-7.5 kg of potassium sulfate per acre, and spray 0.2%-0.3% potassium dihydrogen phosphate solution 2-3 times on the foliar surface.
3. Calcium deficiency yellow leaves. The growth point is dead, the upper leaves are close to the growth point, the leaf margin is dead, the leaf shape is mushroom-like or parachute-shaped, the veins are yellowed and the leaves become smaller; the root system is poorly developed, and few melons are formed. Control method: spray 0.3% calcium chloride aqueous solution on the foliar surface, spray once every 3-4 days, and spray 3-4 times continuously.
4. Lack of magnesium and yellow leaves. After the cucumber plant has 16 leaves, it is easy to onset. The growth of the whole plant is not obviously inhibited, the chlorotic between the veins turns yellow, the leaf margin is green, or there are green spots remaining and no curl. Control method: Foliar application of 0.8%-1% magnesium sulfate solution, once every 7-10 days, continuous spraying 2-3 times.
5. Wounded yellow leaves. Yellow leaves caused by poor roots or root injury are the main cause of cucumber yellow leaves. This yellow leaf is mainly caused by excessive watering and fertilization, or caused by roots caused by continuous cloudy days after watering. The main symptom is that the leaves of the plants are generally yellow, especially the top leaves are small, the growth is slow, and the stagnation occurs in severe cases. Control methods: foliar application of multi-element foliar fertilizer plus 600 times liquid cytokinin; application of rooting seedlings or chitin, etc., promote root growth, prevent leaf senescence, and promote leaf greening.
6. Cucumber salt damage. Cucumber plants are weak, the leaves become smaller, the internodes become longer and longer, the leaves are chlorotic, and then the golden rims are formed, sometimes accompanied by the appearance of the beaks. Prevention and treatment methods: The most fundamental method to prevent soil salt accumulation is to adhere to the application of organic fertilizers, scientific and rational application of chemical fertilizers, and excessive application is strictly prohibited.
7. Downy mildew yellow leaves. Downy mildew is a disease that occurs frequently during the birth of cucumber and is highly harmful. At the onset of seedling stage, the leaves chlorotic and yellow, and finally die. The onset of adult stage leaves began to show water-stained yellow small round spots on the back of the leaves, especially in the morning, and gradually developed into yellow-brown polygonal lesions. Under high temperature conditions, the back of the lesion showed a gray-brown mold layer. In severe cases, the lesions were sliced, the whole leaves were yellowish brown, and the leaf margins were curled and withered. Control method: use 58% toxic mycelium, manganese zinc wettable powder 500 times solution, 72% gram dew WP 600 times solution, 75% chlorothalonil WP or 50% carbendazim WP 600 times Foliar spraying is applied once every 7 days, generally 3-4 times.
8. Cucumber root knot nematode disease yellow leaves. Root knot nematode disease mainly affects the lateral roots and fibrous roots of cucumber, and the roots of the roots or lateral roots produce knobs of different sizes, light yellow to yellowish brown. The symptoms of the aboveground part of the mild diseased plants were not obvious. When the disease was severe, the plants were obviously dwarfed, the melons were few and small, the leaves were chlorotic and yellow, and the aerial parts of the plants appeared wilting or gradually yellowing at noon on sunny days. Finally, the plants died. Anatomical root knot, there are many slender and creepy milky white nematodes parasitized in the diseased tissue. Control method: Irrigation with 1.8% avermectin EC 1500 times or 70% phoxim EC 1000 times, 7-10 days of irrigation, can be 2-3 times, with 300 per pot. -500 ml.
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