Hi Alain,

I noticed I get the best problem when I water with water from the rainwater tub (Which has some algea in it) and have dilluted fertilizer in that water. Not done any testing, but this is gut-feeling. I get a bit of slimey stuff on the topsoil

leatherback wrote:

Ì find I get algea with certain fertilisers & not letting the soil dry out enough)

LB... I believe at the end you are going to be right. I don't have any hard evidence either, but since I stopped fertilizing my Ficus the white dusty thin stuff that was affecting my tree it hasn't come back. Well, and to be completely honest, I also cut a bit the amount of water I was providing it. Possibly the combination of both have finally paid off... Fingers crossed

Alain