What is the disease that causes yellowing cucumber leaves and how to treat it?

Cucumber leaves play a great role in plant growth. If the cucumber leaves turn yellow, it will have a great impact on the yield and quality of the cucumber. So what disease causes yellowing of cucumber leaves and how to treat it? Let’s learn more about it below.

1. Downy Mildew

Symptoms: Initially, chlorotic yellow spots appear on the leaves. The yellow spots are generally about 1 cm in diameter and polygonal in shape. As the infection deepens, the contrast between the chlorotic yellow spots and the surrounding healthy leaves becomes increasingly clear. On rainy days or mornings with high humidity, the back of the leaves will appear waterlogged and a gray-black mold layer will appear.

Treatment method: Mancozeb, Mancozeb, Cypermethrin, Mancozeb, etc. can be used. The spraying should be mainly on the back of the leaves, and the frequency should be about once a week.

2. Bacterial angular spot

Symptoms: The initial symptoms are the appearance of chlorotic yellow spots on the mesophyll between the veins. When the humidity is high, the back of the leaves will also appear waterlogged. In the later stages of the disease when it is more serious, pus will flow out of the lesions, and when the air is dry, it is easy to break and cause perforation.

Treatment method: You can choose Chunlei Wangtong, agricultural streptomycin, and Kesaidi, and the frequency of spraying is once every 7-10 days.

3. Fusarium wilt

Symptoms: The typical symptom is that under good temperature, light and ventilation conditions, the leaves wilt and gradually turn yellow, which is sometimes mistaken for lack of water.

Treatment method: You can choose quinoline copper, carbendazim, and Biotide. The main application method is root irrigation. After diluting the concentration according to the instructions, the amount of medicine for each plant should be more than 200 mg, once every 3-5 days, for 3 consecutive times.

4. Target spot disease

Symptoms: In the early stage of the disease, crystal-like spots appear on the cucumber leaves. The spots are small and irregular. At the beginning, they are half the size of a sesame seed. As the disease worsens, the spots expand outward, reaching about 10 mm and are prone to perforation.

Treatment method: Use 1000 times diluted benzylchlord, or 800 times diluted 70% thiophanate-methyl + 1000 times diluted pyraclostrobin + 1000 times diluted benzylchlord + brassinolide to spray the whole plant.

5. Deficiency

Symptoms: The middle and upper leaves turn yellow. The elements that may be in short supply are mainly zinc, calcium, iron, etc.

Treatment method: In case of zinc deficiency, spray 0.2% zinc sulfate. In case of calcium deficiency, spray 0.2-0.3% calcium chloride on the leaves. In case of iron deficiency, spray 0.5% ferrous sulfate.

Symptoms: Yellowing of the middle and lower leaves may be caused by insufficient supply of elements such as potassium, nitrogen, and magnesium.

Treatment method: To supplement potassium fertilizer, spray 0.4% potassium dihydrogen phosphate; to supplement nitrogen fertilizer, spray 1.5% urea on the leaves; for magnesium deficiency, spray 1-2% magnesium sulfate on the leaves.

That’s it