Do you know why my grape leaves are falling down?

[Jemma]

My grape vine just celebrated her first birthday. She grew so much this spring and was looking gorgeous, then last week her leaves started turning yellow/brown and have dropped. Someone told me it looks like powdery mildew but the google images do not look the same to me. Can you identify the culprit?

 

[LIcenter]

All the leaves above the trellis look fine. My guess is it's dropping lower leaves to save energy for the new growth above. I'm not seeing any powdery mildew either.

 

[Jemma]

It started growing late April and was that big by May. All of the leaves were green up until it got really hot. So could it be they fell off so quickly to conserve the top?

 

[Jemma]

When I googled Downey mildew it sorta looked like it.

 

[Chuck]

My grape vine just celebrated her first birthday. She grew so much this spring and was looking gorgeous, then last week her leaves started turning yellow/brown and have dropped. Someone told me it looks like powdery mildew but the google images do not look the same to me. Can you identify the culprit?

It looks just like spider mite damage to me. In fact on the last picture I can see what appears to be a spider mite web attached to a dead leaf and a green leaf. Cut off all of dead and even slightly affected leaves and start a spray regimen of Neem oil. Use a spinosad based insecticide as a soil drench too. Use the Neem spray every 4-6 days for a month. The soil drench once. The reason for spraying so much is that spider mites have a very fast and complicated reproductive procedure and it will take this long to completely stop it.