I have two grape plants. One of them developed some pest or disease. The leaves look like this:

Does anyone know what this is or what to do about it? My other grape vine is huge and healthy. The one with these is small and doesn't look too good. Is this treatable? Do I need to worry about it spreading? Should I torch the sick plant? Is the healthy plant likely sick anyways and just not showing symptoms yet?

The sick one is growing in a fence around my yard. The healthy one on my patio. There are probably 10 feet of mostly grass between the plants.