Causes of Yellow Leaves of Cucumber and Its Control Measures

During the growing period of cucumbers in greenhouses, if malnutrition, improper management, or infection by certain diseases, the leaves may turn yellow, affect the growth of cucumbers, and even cause no harvest. The reasons for the yellowing of cucumber leaves and their prevention methods are as follows:

One, lack of yellow leaves

The lack of yellow leaves is divided into middle and lower old leaves first yellow and middle and upper young leaves first yellow. The old leaves in the middle and lower parts are yellow, and the missing elements are mostly easily reusable elements in the plant, such as potassium, magnesium, and zinc. The middle and upper young leaves are yellow, and most of the missing elements are elements that are not easily reusable in the plant body, such as calcium, sulfur, and iron.

1. Magnesium deficiency: After cucumber plants have 16 leaves, they are susceptible to disease. The growth of the entire plant is not significantly inhibited. The veins turn green and yellow, and the leaf margins are green, or there are green spots and no curl. Control can be sprayed on the surface of 0.8% ~ 1% magnesium sulfate solution, every 7 to 10 days 1 time, continuous spraying 2 to 3 times.

2. Potassium deficiency: Plant growth was not significantly inhibited. Leaf margins were slightly yellowed during the early growth period, and then expanded to veins; chlorosis and necrosis of leaf margins were observed in the mid and late stages of growth. Occasionally, the leaves lost chlorosis to necrotic spots; melon strips were short and expanded. bad. Control can be sprayed on the foliar 0.2% ~ 0.3% potassium dihydrogen phosphate solution 2 ~ 3 times.

3. Zinc deficiency: no significant inhibition of plant growth, from the middle position of the chlorosis; veins obvious, the veins gradually fade, the edge of the yellowing to brown. Leaves dead, slightly eversion or curling leaves. Control can be sprayed on the foliar 0.2% zinc sulfate solution.

4. Calcium deficiency: The point of growth is withered. The upper leaves near the growth point are smaller, the leaf margins are withered, the leaf shape is mushroom-like or parachute-like, the veins between the veins yellow and the leaves become smaller; the roots are not well developed and there are few melons. Control can be sprayed with 0.3% calcium chloride aqueous solution, spraying once every 3 to 4 days, continuous spraying 3 to 4 times.

5. Sulfur deficiency: The growing point does not die, the leaf color is light green and the stem is small. Control the upper leaf surface by spraying 1% potassium sulfate solution.

6. Iron deficiency: The new leaves and axillary buds begin to turn yellow and white, especially the leaves and new leaf veins near the upper leaves and growth points are yellowed first and gradually chlorotic, but no necrotic spots appear between the veins. Control spraying on the upper leaf surface of 0.1% to 0.5% ferrous sulfate aqueous solution.

Blight yellow leaves

Fusarium wilt is commonly known as "death." At the early stage of disease, the lower leaf surface of the diseased plant chlorosis and yellowing, and afterwards, the leaves wilted at noon and recover sooner or later, and no longer recover after several days. Leaf color gradient yellow-green to tan, from bottom to top gradually extended to the whole plant. The main vines near the ground were rotted, thinned or longitudinally cracked, gradually dried up, and the whole plant died. Some plants showed half withered and half normal. Rhizome disease has an amber gel, and when the humidity is high, white or pink molds appear on the surface. When you break off the stem or main root, you can see the interior turning brown.

Prevention and treatment: Use 50% carbendazim WP 500 times solution or 50% thiophanate-methyl wettable powder 500 times to water the root circumference of the plant, each strain should not be less than 250 ml, and every 5 to 6 days should be used for irrigation. , Even irrigation 2 to 3 times.

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