One of the two honeysuckles in our back garden is suffering very badly
from white, powdery mildew. It's being grown up a trellis to help
obscure the back wall of our garage and is now about six feet high
but, the young growth at the top of the plant apart, the foliage is
now looking very unhappy.

Is there anything that I can do to kill the mildew? The information
I've found on the web doesn't talk about cure, only prevention;
spraying the plant with a fungicide, keeping it watered (which I
thought we *had* been) and burning mildewed foliage.

If I attacked the plant with fungicide, would that clear up the
problem, or is existing mildew there to stay?

Cheers,

Gareth