white mould on phormium

I know phormiums are prone to Mealy Bug (Wooly Aphids) so it could be that. Scrape some of the 'fluff' off and if you see little critters walking around then that's what it is. If it is the case you will need a systemic pesticide such a Provado to kill them off. Organically I've read some people use soap liquid, alcohol and even garlic to kill them.

Not sure about the copper spots, it could be where things have been nibbling at them.

As long as the new leaves are healthy I wouldn't worry too much. Clear away the nasty bits and don't compost them as if it is a disease you might spread it around. It's very humid under a Phormium and lots of mould would like it!

hi, i just discovered the same mould around the base of my phormium. did you treat yours or not??? new growth seems fine tho.

Hello, I just discovered the same white moldy patches all over my Flax plant. It' actually a fungus and does need to be treated. It's called
SCLEROTINIA DISEASE, WHITE MOLD
OR WATERY SOFT ROT

You have to completely get rid of the infected plants, especially if it's all over the leaves and the plant has copper spots. The white fungus grows internally as well but is hard and black inside the stems of the plant.

Once you get rid of the infected plants you need to treat the soil with the correct fungicide.

Then you'll need to find out why that area was susceptible, like a poor drainage problem, etc.
This is what I've learned, hope that helps.