White grubs can feed on potatoes, especially if they are being grown in an area that was formerly lawn. The Colorado potato beetle, which affects crops of potatoes all over the country, is the most likely culprit in its immature form.
Damage to the potato crops can vary. Some potato pests will feed on the tuber portion, while others will feed on the leaves. Some plants can become completely defoliated to the point where they can no longer make food for themselves via photosynthesis.
Cultural methods are more effective than chemical ones in controlling potato pests. Controlling weeds and grasses nearby will reduce additional temptation for pest species to invade your potato crop. Crop rotation will help reduce incidence of infestation as well.