Planting resistant varieties appears to be today's only solution to the closely related Imperial Valley lettuce problems of (I) internal rib necrosis (see photo) which develops in the field during maturity, and (2) rusty rib (see cover) which develops after harvest during cold storage. The popular variety Climax is highly susceptible to both.

Cooperating in these studies were A. J. Mackenzie, Superintendent, and R. O. Standridge, Agricultural Research Technician, both of USD A Southwestern Irrigation Field Station, Brawley, California; and Adolph Van Maren, County Director and Farm Advisor, Imperial County. Photography were by Albert O. Paulus, Extension Plant Pathologist, University of California, Riverside.