Cucumbers

Question

Why do the leaves on my plants have like a dust on them?

Answer 1

This is likely Powdery Mildew.
It can be caused by damp conditions and lack of air flow around the plants.
You can treat your plants with a fungicide.

Here is a link with more information.
https://www.gardeningknowhow.com/plant-problems/disease/get-the-cure-for-powdery-mildew.htm