Answer: Wish I could give you a positive diagnosis, but without examining the plant, I can only guess. If you're seeing a fuzzy black growth, I'd say it's a fungus that's spreading. You should be able to wipe it off the stem and leaf, then improve the growing conditions so the fungus won't develop again. If the stem tissue has actually turned black, it might be that a disease has developed due to faulty growing conditions (overwatering in winter, leaving water on plant leaves and stems at night, or poor air circulation around the plant). If this is the case, you may be able to cut away the affected tissue and improve the growing conditions so your palm has a chance to recover. It may also just be a sunburn due to direct sunlight on that side of the trunk. For positive identification of the problem you can take your plant to the local Cooperative Extension office (323-838-8330 ). The friendly people there will give you suggestions for control of the problem.
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