Cultural methods include field selection, management of weeds in crop rotation and preventing the entry of new weeds in to a field. Growers should be familiar with weed problems from previous crops because this information is essential for field selection. It is important to select a field free from weed problems, which cannot be controlled by tillage and herbicides used in the production of potatoes. Potato growers should attempt to control perennial weeds such as Canada tistle and quack grass, in other crops in the rotation because there are few herbicides registered for use on potatoes that are effective against these weeds. It is also important to prevent the entry of new weeds into the field via equipment, livestock and manure. Ideally, escape weeds should not be allowed to set seed.