I'm sorry, but I don't know if you can. I wouldn't eat cucumbers from those plants anyway.

Yes you can. You need to ventilate the greenhouse to stop too much damp air and you could use 1 part milk to 9 parts water and spray the plant. Mildew won't hurt you as long as you wash the cues before you eat them, which you would do anyway. I used to take off the occasional mildew leaf. Trouble is if you make it too dry in there you will get red spider mite. It's a balancing act!

I'll give it a try too Cammomile. thanks

You can try doing as Cammomile suggests, Bootsgarden, but both these plants get downy mildew as well as powdery mildew - if its downy mildew, unfortunately, there is no treatment, so try the milk spray and increase air flow, but if it all just gets worse, it may well be downy mildew.