|What must I do for white spots on cucumber plants.
|The white spots can be sunburn or might be powdery mildew, a fungal disease. If the white is a coating on the leaves, cut away the infecting leaves so the disease doesn't spread to the rest of your plant. To reduce additional infections, avoid overhead watering to help reduce the relative humidity. Remove and destroy all infected plant parts (leaves, etc.). Selectively prune overcrowded plant material to help increase air circulation. This helps reduce relative humidity and infection. If cultural controls fail to prevent disease buildup, or if the disease pressure is too great, an application of a fungicide may be necessary. These include: sulfur, neem oil (Rose Defense, Shield-All, Triact), triforine (Ortho Funginex), or potassium bicarbonate (Kaligreen, First Step) Chemicals are most effective when combined with cultural controls.