Cucumbers are a common vegetable and fruit, delicious and nutritious, and therefore loved by everyone. However, during the growth stage of cucumbers, there is an insignificant situation, that is, the cucumber leaves turn yellow. How do cucumber leaves turn yellow? How should it be prevented?

What causes the cucumber leaves to turn yellow

1. Yellowing of new buds caused by unscientific fertilization. The data shows that the proportion of nitrogen, phosphorus, and potassium required for the growth and development of cucumbers is generally considered to be: 1.68:1:1.53. Because of the extensive promotion of equipment cultivation in recent years, the market is concerned, and the yield of cucumbers has continued to increase, the situation of excessive application of base fertilizer and insufficient potassium fertilizer is also widespread, especially during the flowering and fruit setting period, potassium deficiency occurs a lot. The main symptoms are that the leaves and leaf edges turn yellow, and then gradually expand to the veins between the petioles, and in severe cases, the leaves wither and curl, the fruit growth is hindered, and deformed fruits such as high proportion, thin waist, and head bowing often occur.

In addition, excessive base fertilizer, especially excessive ammonium nitrogen, will continue to immediately affect the cucumber’s digestion and absorption of calcium fertilizer, causing calcium deficiency. The specific manifestations are: stunted growth of new buds, lack of leaf edges, withered leaves, and light yellow or brownish soft spots. The yellowing of new buds reported by netizens may be related to this level of cause.

2. Small green spots on the yellow leaves caused by brown spot disease. Brown spot disease is a key disease that affects cucumber leaves, with lesions in a ring-shaped, elongated, or irregular shape, deep brown to dark red, diameter 0.5-13mm, with distinct or indistinct edge, and showing a chlorosis to pale yellow halo. The mold layer is rare. The pathogen is Cucumis vegetable Alternaria, a bacterium in the subclass Fungi Imperfecti. The pathogen overwinters on the soil残体 in the form of mycelium or sporulation. In the next spring, it conducts primary and secondary infections with conidia, and spreads by air currents. Under conditions such as warm and humid weather, excessive application of base fertilizer, and continuous cropping, this disease is prone to occur more severely.

What to do if the cucumber leaves turn yellow

1. Implementing crop rotation and intercropping of non-melon crops for 2-3 years or more, using sufficient decomposed compost organic fertilizer, fertilizing according to the proportion of nitrogen, phosphorus, and potassium required for the growth and development of cucumbers, and moderately topdressing with calcium nitrate and borax sand of 1-2Kg per mu to improve the disease resistance and working ability of the main stem.

2. Prevention by using a drug sprayer:

(1) 750 times dilution of 80% zoxamide·霉素 wettable powder, 750 times dilution of 60% calumet calcium, 750 times dilution of 21% calumet boron.

(2) 428 times dilution of 41.4% benomyl·oxystrobin composition (25ml powder, 10g granule), 300 times dilution of 10% high boron active potassium calcium powder.

(3) 1500 times dilution of 25% dimethomorph suspension, 750 times dilution of 60% azoxystrobin·mancozeb wettable powder, 300 times dilution of 10% zinc calcium boron granule.