What is wrong with the yellowing of cucumber leaves? What to do?

Now cucumber greenhouse planting or open-air planting is very common, people have a very comprehensive grasp of cucumber planting and cultivation technology, but they still often encounter the situation of cucumber leaves yellowing, and deeply troubled the majority of growers and friends. So, what causes cucumber leaves to turn yellow? And how to cure it?

I will briefly introduce the 5 causes of yellowing of cucumber leaves and the corresponding prevention and control methods, I hope it can help you.

First, the prevention and control measures for the yellowing of cucumber leaves caused by changes in the external environment. When there is a sudden change in temperature, humidity and light, it will cause the physiological yellowing of cucumber leaves. The prevention and control of this situation is as follows:

The growth environment of cucumber meets the growth needs of cucumber, cucumber is a typical thermophilic plant, and its fertility suitable temperature is 10 32. The temperature requirement is high during the day, about 25 32, and the temperature requirement is low at night, about 15 18. The suitable temperature for photosynthesis is 25 32.

Therefore, if the above environmental conditions are met, the yellowing of cucumber leaves can be prevented.

Second, the control measures for the yellowing of cucumber leaves caused by excessive watering and excessive water. When this happens, the leaves of the cucumber plant will generally turn yellow, especially the top leaves are small, the growth is slow, and wilting will occur in severe cases. The most suitable soil relative humidity for cucumber is 85% 90%, cucumber has a strong ability to adapt to air humidity, and the relative humidity of the air at night can reach 90% 100%, but the humidity is too high and the time is too long, it is easy to cause diseases.

Therefore, do not water cucumbers more than once to prevent the root system from rotting due to lack of oxygen due to excessive moisture.

Third, the prevention and control measures of yellowing of cucumber leaves caused by excessive fertilization. Although there is a lot of demand for nutrients in the process of cucumber planting, it is not possible to arbitrarily increase the amount of fertilizer, if too many nutrients will cause excess nutrients in cucumber plants and cause yellow leaves. Therefore, the fertilization of cucumber needs to be carried out according to different growth stages, for example, seedling fertilizer is used at the seedling stage, and a balanced macro-element fertilizer of 20-10-20 can be applied in an appropriate amount, and a balanced and high potassium fertilizer should be applied in the middle and late stages, and 20-20-20 and 15-15-30 can be applied.

Seedling stage generally top dressing once or twice can be, in the late stage every 10 15 days or so to apply once to meet the demand for nutrients, the fast-acting water-soluble fertilizer is faster than the traditional fertilizer absorption, the effect is also fast, and the yield is obvious. Of course, it is essential to plant cucumber before base fertilizer, pay attention to apply more organic fertilizer and microbial fertilizer.

Fourth, the lack of medium and trace element fertilizer caused by the prevention and control measures of cucumber leaf yellowing. Cucumbers also have a lot of demand for trace elements, such as magnesium, boron, iron, zinc, calcium and other trace elements. If there is a large shortage of these elements, the quality of cucumber plants and fruits will be reduced, so these trace elements should also be supplemented in the middle and late topdressing process.

Cucumber foliar fertilizer can be sprayed to comprehensively supplement the nutrients needed for cucumber growth, so as to improve the quality of cucumber plants and cucumbers, and enhance the resistance of cucumber plants to common diseases.

The temperature is too high or too low will cause the leaves to yellow, lack of fertilizer, no fertilization will cause malnutrition to cause the leaves to yellow, cucumbers are better planted in greenhouses, not easy to occur these problems.

Environmental mutations lead to yellowing of cucumber leaves, sudden changes in temperature, humidity and light, root damage, cucumber double mildew, watering many times to dilute the concentration of soil solution, and reduce the amount of chemical fertilizer in the future fertilizer process.

1. Element-deficient yellow leaves:

Element-deficient yellow leaves can be divided into two situations: middle and lower old leaves first yellow and middle and upper young leaves first yellow. The middle and lower leaves are yellow, and most of the missing elements are the elements that are easy to be reused in the plant, such as nitrogen, potassium, magnesium, zinc, etc.

1) The growth of the whole plant is resisted, and the whole leaf of the older leaves lacks green, which is nitrogen deficiency. The control countermeasure is to spray urea solution 2-3 times on the foliar surface.

2) The whole plant growth has no obvious resistance to the loss of green and yellow, the loss of green and yellow between the leaf veins, the leaf edge is green, or there are residual green spots, no curl, magnesium deficiency. The control countermeasure is foliar spraying of 1%-2% magnesium sulfate solution.

3) There is no obvious inhibition of plant growth, and the leaf edge loses green to necrosis, and sometimes there are green to necrotic spots on the leaves, which is potassium deficiency. The control countermeasure is to spray potassium dihydrogen phosphate solution 2-3 times.

4) There is no obvious resistance to plant growth, and the whole leaf has green to necrotic spots or streaks, which is zinc deficiency. The control countermeasure is foliar spraying of zinc sulfate solution. The middle and upper young leaves are yellow first, and most of the missing elements are the elements that are not reused in the body, such as calcium, sulfur, iron, etc.

Solution: 1) The growth point is dead, and the leaves lack green and shrink to necrosis; The root system is underdeveloped, and it rarely bears melons, which is calcium deficiency. Control measuresFoliar spraying of calcium chloride solution 2 times a week.

2) The growth point does not die, the leaf color is light green, and the stem is small and lacks sulfur. The control countermeasure is foliar spraying of 1% potassium sulfate solution.

3) The growth point does not die, and the leaf color is yellow and white, which is iron deficiency. The control countermeasure is foliar spraying of ferric sulfate solution.

2. Downy mildew yellow leaves:

Downy mildew is a common and serious disease that occurs during the growth period of cucumbers. At the seedling stage, the leaves turn green and yellow, and finally die. At the adult stage, the leaves are diseased, and they begin to appear water-stained yellow round spots on the back of the leaves, especially in the morning, and gradually develop into yellow-brown polygonal lesions with yellow-green edges.

Under high temperature conditions, a gray-brown mold layer grows on the back of the lesions, and in severe cases, the lesions become patches, the whole leaves are yellow-brown, and the leaf margins are curled and wilted. The control countermeasure is to use 500 times of Ruifuxin, manganese zinc 58% WP or 75% chlorothalonil WP, 50% lysophilam WP600 times solution for foliar spraying, once every 7 days, generally spraying 3-4 times.

3. Yellow leaves of blight:

Fusarium wilt is commonly known as "dead seedling".In the early stage of the disease, some leaves wilt at noon, and can recover in the morning and evening, and do not recover after a few days. The leaf color gradually changes from yellow-green to yellow-brown, and gradually expands to the whole plant from bottom to top.

The main vine near the ground is brown and water-stained and rotten, thinning or longitudinally cracked, gradually drying up, and the whole plant is dead. Amber gelatinous flows out of the diseased part of the rhizome, and when the temperature is high, white or pink mold is produced on the surface, and when the stem or taproot is broken, the inside can be seen to turn brown. Prevention and control measures:

It is to irrigate the roots with 50% carbendazim WP500 times, or methyl tobujin 50% WP500 times, each plant is not less than 250ml, irrigated once in 5-6 days, and irrigated 2-3 times.

Teach you three tricks to keep the leaves of green plants from yellowing!

There are many reasons, and you can't generalize, look at the changes in the surrounding environment before and after the leaves turn yellow, and compare the changes before and after.

There are several reasons for the yellowing of cucumber leaves:One is to water it too much, the root system will rot due to lack of oxygen in the soil, and yellow leaves will appear.

The second is to apply too much fertilizer to it, and if there is excess nutrition, it will also cause the leaves to turn yellow.

The third is to be directly exposed to the sun by the intensity of summer.

Fourth, there is a lack of trace elements.

Hello! For example, cucumber rod spore leaf spot (also known as cucumber brown spot disease). This disease has occurred more often in Liaoning in recent years. In general, early prevention should be taken. The pesticides used are imimidide and difenoconazole (Shigao).

In addition, if you plant cucumbers again, there are some measures. When grafting cucumbers and pumpkins with seed sterilization, it is necessary to pay attention to the pumpkin seeds that do not carry bacteria. Soak cucumber seeds and grafted black-seeded pumpkin seeds in warm water at 55 for 30 minutes.

Agricultural measures: Diseased fields should be rotated with non-melon crops for more than 2 years. Completely remove the diseased and residual plants in the field and then turn the soil deeply to reduce the source of the initial invasion in the field.

Apply sufficient basal fertilizer, top dressing in a timely manner, avoid partial application of nitrogen fertilizer, increase phosphorus and potassium fertilizer, and apply boron fertilizer appropriately. To prevent premature senescence of cucumber plants, pay attention to wind and dampness after watering, and remove diseased leaves at the beginning of the disease. Pharmaceutical prevention and control:

At the beginning of the disease, use 75% chlorothalonil wettable powder 500 times, or 70% mancozeb wettable powder 500 times, or 50% foomet double wettable powder plus 65% zeb wettable powder (1:1) 500 times, or 75% chlorothalonil wettable powder plus 70% carbendazim wettable powder (1:1) 500 times, or 75% chlorothalonil wettable powder plus 50% sucrin wettable powder (1:

1) 1 000 times liquid and other chemical sprays, once every 7 days, continuous prevention and control 2 3 times.

1.If the old leaves are yellow, if you find that the middle and lower leaves of the cucumber lose green and yellow, and the color of the upper young leaves is normal, this situation often occurs in the middle of growth, the main reason is that the vegetative growth is fast, and the nitrogen fertilizer in the soil is insufficient.

2.Yellowing of new leavesIf the middle and lower leaves of the cucumber are normal, but the newly grown leaves at the top are yellow, this symptom is generally a deficiency symptom, and iron deficiency is usually the most likely. The cause of soil iron deficiency may be excessive soil moisture, especially after heavy rain, waterlogging in the ground, lack of oxygen in the soil roots, and weakened fertilizer absorption ability.

We need to remove water from the soil in a timely manner.

3.Yellow spots on the whole leaf If there are yellow spots on the new and old leaves of cucumbers, it is most likely that a disease has occurred, the most common being downy mildew of cucumbers. Cucumber downy mildew is a frequent disease of cucumbers, once this yellow spot is found, it should be prevented and controlled in time, chlorothalonil, mancozeb can be used in the early stage, and downy mildew can be used in the middle and late stages.