Potato wart symptoms can be found on all underground plant parts except roots. On stems, galls form at the base of the stem; initially white but turning black when decaying; may be as small as a pin or as large as a fist; the surface is rough and corrugated-warty in appearance. On tubers and stolons, eyes develop cauliflower-like swellings; when formed underground, they are the same color as the potato skin, darkening with age, or green if exposed to light. Typical warts are soft and pulpy and easier to cut than a healthy tuber. On aerial buds - Small greenish warts form in the position of the aerial buds at the stem bases.