Red Stele Root Rot Identification Red stele, caused by Phytophthora fragariae , is a serious fungus disease of strawberries in the United States. This fungus attacks plants during late winter and spring. It is most destructive in heavy clay soils saturated with water. Infected plants appear stunted and lose their shiny green luster. The plant's younger leaves often have a metallic, bluish-green cast.
Older leaves turn prematurely yellow or red.
Diseased plants wilt in dry weather and often die before the fruit starts to ripen. Because pathogen spread is favored by water, red stele may be fairly well distributed over an entire strawberry patch during a cool, wet spring. Normally, however, this disease is prevalent only in the poorly drained areas of a field or patch. Red stele usually does not appear in a new planting until spring of the first bearing year. It is most evident from full bloom to harvest.