Spots on taro, algal, slime or what? New Caledonia Minimize

January 2012. A question from New Caledonia: what are these spots on taro?

Some members thought that the spots were algal, possible Cephaleuros species, but others did not. But that was unlikely for the following reasons:

  • algal spots are slow growing and would be unlikely to get to that stage on a lef that lasts on about 40 days
  • algal spots rarely form on leaves in the sunlight; they are usually on the undersurface of leaves
  • the spots scape off with the fingernail, and the plant tissue is not attacked; this is unlike Cepaleuros whihc grows beneath the cuticle
  • the edges of the spots are sharply defined, whereas Cephaleuros looks hairy and tapers slightly at the edges where it is almost clear

It was suggested that the spots might be the fruiting bodies of a slime mould. Each spot is possibly an aethelium with the 'skin' being the peridium holdiing a mass of spores.