There were two posts where I was being completely serious about it most likely being blight and how to treat it.
If it's a fungus, the spores for it are already in your garden. Pulling up the taters will just delay the spread to other plants. Treat now, while you can stay on top of it.
From Jerry Baker's book:
1/2 cup of molasses
1/2 powdered milk
1 tsp baking soda
1 gal warm water.
Mix the first three into a paste. Use an old nylon stocking or such and steep in the water for several hours. Strain, spray the liquid on your plants to control fungus.