Sounds like Mildew, Mildew thrives in dry shady areas, water your
plants regulary.

hope this helps.

Gardening_Convert wrote:
I have some marjaram that has been thriving very close to an old tree
stump.

I noticed yesterday when I was weeding that there is some white mould
or fungus on the soil at the base of the stems of the marjaram.

Any ideas what this is , could it be a fungal spreading from the tree
stump , is it a problem ??