Potatoes emerge approximately 15 to 30 days after planting. In that time, a significant number of weeds can germinate. An application of a non-selective herbicide just prior tto emergence of potatoes will control annual weeds and set back perennial weeds. Burn-off herbicides are not affected by tillage operations. If hilling is performed just prior to emergence of potatoes than a pre-emergent herbicide may not be required.