Is there a time when I should stop watering my potato plants prior to the full harvest? I have heard you should stop watering them when the plants start to die down, but I'd like to hear from the expert. Thank you.
Yes, stop watering the potatoes after the foliage turns yellow and dies down.
This allows the potatoes to mature to the right stage before harvest.
If you continue watering the potatoes may rot in the ground.
Here is a great link about harvesting potatoes.