Answer: What you describe sounds like a fungal diseas called powdery mildew. Once it has overtaken your vegetables, there's not much hope in stopping its progress. For infected vegetables and other annuals, remove as much of the plant and its debris in the fall as possible. This decreases the ability of the fungus to survive the winter. Do not compost infected plant debris. Temperatures often are not hot enough to kill the fungus. 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), ornamental use only, or potassium bicarbonate (Kaligreen, First Step) Chemicals are most effective when combined with cultural controls. Apply fungicides at seven- to 14-day intervals to provide continuous protection throughout the growing season. Follow the instructions on the fungicide label for use on specific plant species, varieties, rates to be used, timing of applications, and waiting periods before harvest. Hope this information is helpful.
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