Reasons for which leaves of cucumbers can change their color a lot. In most cases, if you identify the cause in time, you can avoid a mass extinction of plants and therefore crop losses. Recurrent frosts is the only case that can adversely affect planting and already frostbitten foliage of cucumbers you can help plants can't. If you grow cucumbers in the open ground, be sure to follow the weather forecasts, planted seedlings to a permanent place according to weather conditions in your region and be sure to keep a special materials that you will be able to cover the plants during cold weather (lutrasil, spunbond, etc.).
Also yellow leaves of cucumbers can damage diseases. Cucumbers - culture, which is often "attacked" fungal disease, the most common are "powdery mildew", Ascochyta-leaf spot, Anthracnose, root rot and white. With all these diseases in a certain period of time the leaves of cucumbers acquire color from yellow to brown, shrivel up and fall off. If you notice on the leaves of cucumbers slightest white or yellow blotches, do not neglect the treatment with antifungal drugs. To minimize the infection of plants by fungus, timely watering culture, and only warm water.
Don't forget to feed the seedlings. The fact that a shortage of potassium, phosphorus and nitrogen can cause yellowing of the lower leaves. It is easy to guess that the soil of these minerals will rectify the situation. Currently on sale you can find a lot of complex fertilizers for cucumbers, use them or make your own organic fertilizer on the basis of mullein, herb infusion and ash.
Wrong choice of the landing site can also lead to yellowing foliage. Cucumbers like well-lit and well-ventilated area, so try to make a bed where these conditions are met.