Poorly Cucumbers ????

[Minty]

Please can anyone tell me why my outdoor cukes leaves are covered in a dusty mould like thingy(technical term) and crumbling to dust when touched ???
And maybe how to remedy it.
Thanks Minty XXXXXXX

[taff]

Sounds like downy mildew. Courgettes and some squash [not sure if all types do?] get it as well.
The leaves start off having white patches, which can spread to all the leaf.
No idea how to remedy it, someone will be along shortly....