Worldwide distribution. On coconuts, date palms, ornamental palms. A minor fungal disease. Unlikely to affect yield of coconuts or date palms; however, possibly a 'cosmetic' disease on palms grown for landscaping, or a problem in the nursery.
It is not a smut disease. Small, grey or black pustules, 1.5 mm diameter, emerge through the leaf, mainly on the top surface. Spores and sterile threads emerge from the pustules.
Spread by spores in wind and rain.
Cultural control: avoid over-crowding in coconut nurseries. Ideally, grow coconuts in polythene bags and space them at least 1 m apart; not economic to attempt to control the disease in the field - no evidence that it effects yield.
Chemical control: if fungicides are required in the nursery, use copper products or mancozeb as protectants, or thiophanate methyl (sometimes formulated with chlorothalonil) as a systemic product.