The potato tuber moth (PTM),Phthorimaea operculella (Zeller), is a pest of solanaceous plants. In Israel it damages mainly potatoes, and tomatoes grown for processing. The PTM favors high temperatures and drought. Under these conditions its development period is short, resulting in overlapping generations and high populations in mid-summer. A phenological study, based on the use of the female sex pheromone, showed that moth flight occurred throughout the year. Large populations of the PTM were present only during the hot season. Populations were highest in the semi-arid Negev, where potatoes are grown on a large scale during two seasons of the year; in other areas, PTM populations were much lower.