White mold on house grown vegetable - Knowledgebase Question

Lakehills, Te
Question by josephburke
October 25, 2009
Okay so here is the deal: I live in a college residence hall (dorm) and I have cucumbers and okra growing in my room. Sadly however, some the cucumbers have grown a white mold that begins to yellow the leaves. I assume that the yellowing is caused by a lack of photosynthesis, but what should I do about the mold?


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Answer from NGA
October 25, 2009

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What you describe sounds like powdery mildew and if so, it is extremely difficult to control once established. Once a plant is fully involved, there's just no stopping the disease. There are some resistant vegetable varieties so be sure to choose those next time you plant. Removing affected plant parts as soon as you see them and using a fungicide can sometimes protect unaffected plant parts, but it doesn't always work.

Your theory about photosynthesis sounds plausible but in this case the disease is killing the plant tissues, which is what is causing the leaf to turn yellow. The early stages of the disease have already killed the tissues - even before you see the white powdery substance. The infectious spores are what makes the substance white and by the time you see the white coloration, the spores have already matured and spread to other parts of the leaf and to other leaves. Eventually you'll see the powdery mildew on other parts of the plants.

Both cucumbers and okra require hot temperatures and plenty of direct sunshine. I don't think they are getting either, even in a sunny windowsill in your dorm. At this point I'd remove the affected plant parts and spray with a fungicide. You may be able to save the plants. If not, toss the plants and try growing something that does not require such warm temperatures and as much sunshine. Snap peas are a good choice; green beans may grow well for you at this time of year.

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