The leaves on my pumpkin plants have what looks like a white mold growing on them.

What is this?

If it is harmful, how do I treat it?

  • 2
    Would be easier to answer if we could see it. Can you post a photo? – Rincewind42 Jul 1 '11 at 9:21
  • Good point. I will have to take some pictures and post when I get back from work this evening. – Mongus Pong Jul 1 '11 at 9:51

This is almost certainly Powdery Mildew (see photo), a fungal disease that prefers high humidity and occurs most often during a spell of cool days and humid nights. A severe attack will destroy plants' leaves and reduce their yield. You can control it chemically with a copper or sulfur-based fungicide, or organically, using the following recipe, which I haven't tried myself but I gather is very effective. It is based on research done by Cornell University:

1 tablespoon each of baking soda (sodium bicarbonate) and either a light horticultural oil or regular vegetable oil, to 1 gallon of water. Shake well before and during application.

Powdery Mildew on Pumpkin Leaves

  • Yes, that is definitely the stuff. – Mongus Pong Jul 1 '11 at 11:34
  • could this happen on eggplant? Our looks very similar. – Mike Ohlsen Jul 1 '11 at 16:18
  • Yes, it often does. – Mancuniensis Jul 1 '11 at 16:21
  • That recipe seems to br working very well! – Mongus Pong Jul 3 '11 at 13:48
  • Glad it's proving effective. Thanks for the feedback! – Mancuniensis Jul 3 '11 at 13:52

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