White dust on clematis and sweet pea

Katstez

Hi, can anyone tell me what the white powder dust like is that has formed on my clematis and sweet peas. Also how do I get rid of it. Have I lost the clematis or shall I just cut it right down and hope it come back next year. Thank you. 

fidgetbones

Powdery mildew due to dryness at the roots. They need a good soaking.

Katstez

Ok thankyou, will do that. To be fair we are quite good at watering our garden.