Question
I'm a bit reluctant to let it happen again just to take a picture. But your description of exudate makes sense. I'm very glad to know about the fungus problem so I can try to ward that off also. I have a spray that I think will help if that happens. If it happens again, however, I WILL get out the digital camera and take a picture. Thanks so much!

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Followup To
Question -
I recently bought one of the dark red sweet potato house plants. I didn't know it needed so much water, and when it got dry it got crystal-like things on some of the leaves and stems. Very thick. I could scrub them off and also found a big clump on the dirt. But whenever it gets the least bit dry it happens again. Is this a pest? or a disease? I can't find anything fitting this discription in any of my gardening books. The plant has new growth, so it's not dying, but the leaves that had this on them don't look quite the same now.
Answer -
Hi Janet,

Sweet potato often gets spots on the leaves caused by a fungus. However, your description of the "crystal-like things" doesn't seem to fit. I suspect it may be exudate, which is a bit like dried perspiration. However, I am not sure of this.

Can you e-mail me a photo ([email protected]) or else provide a more detailed description (size, color, shape, etc.) of the crystals?

Regards,
Will Creed

Answer
Hi Janet,

If there is no permanent damage to the leaves, then I am confident it is not a fungus, pest, or disease problem. Thus, I don't recommend using a fungicide. Apparently, all you have to do is avoid allowing the plant to get too dry and the problem will end.

Good luck and please let me know if you have any additional questions.

Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

You can E-mail me directly at: [email protected]

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