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"False Smut: False smut or Graphiola leaf spot is caused by Graphiola species. This disease is most common in areas of high humidity. Only palms in the Arecaceae family are affected. In South Carolina this includes sabal palmetto (Sabal palmetto), jelly or pindo palm (Butia capitata), Chinese fan palm ( Chamaerops humilis), and Washington palm (Washingtonia robusta).

Infected leaves have small, black, wart-like structures erupting through both leaf surfaces. Tiny filaments may emerge from the black spots. There are usually no symptoms on the youngest leaves."

http://hgic.clemson.edu/factsheets/HGIC2007.htm
http://hgic.clemson.edu/PDF/HGIC2007.pdf

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