Cure for orange dusty mildew?

the_devil_made_me_do_it

I have a potted weeping willow in my garden. I noticed that on the leaves was what I can only describe as an orangey dusty looking mildew on the leaves.

So, I decided to cut off the affected leaves. However, it's reappearing again & I have no clue what I can do to stop it happening. If I don't find a solution, I think it will kill the tree.

I have also took notice of the plants close by & they ain't affected.

Does anyone have a clue what this could be & how I can get rid/stop it attacking the tree?

the_devil_made_me_do_it

It could even be a fungus. It's flat on the leaves.

demystified

It's rust. It's a fungal disease. Spray with Systhane if it's a nuisance.

Trees that are under stress are more liable to fungal diseases than those that are not, is the tree fed and watered regularly?

the_devil_made_me_do_it

I water it if it hasn't already rained & yes it gets fed. In fact re-potted it last year into a much bigger pot.

Where could I buy Systhane?