WHITE POWDER TOP OF LEAVES - Knowledgebase Question

Palm Desert, Ca
Question by LORBRET
January 16, 2010
Any ideas on what this is. Has developed in last month, I also over watered (Ithink) was away. How much water per day?

Answer from NGA
January 16, 2010


What you describe sounds like a fungal disease called powdery mildew. 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. It's possible to overwater plants so instead of sticking to a regimented schedule for watering, water your plants when the soil begins to dry out. Water as usual then wait several days and dig down into the soil. If it is still moist an inch beneath the surface you won't need to water for a few more days; if it is dry, it's time to water. Good luck with your plants!

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