Fusarium Hypocotyl Rot of Sugar Pine in California Forest Nurseries. K. H. Brownell, Department of Plant Pathology, University of California, Berkeley 94720. R. W. Schneider, Department of Plant Pathology, University of California, Berkeley 94720. Plant Dis. 67:105-107. Accepted for publication 3 September 1982. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-105.

A hypocotyl rot disease of sugar pine is described that caused severe losses in less than 3-mo-old seedlings of Pinus lambertiana, Abies concolor, and A. magnifica in California forest nurseries. Fusarium oxysporum was found to be the causal organism. Greenhouse-grown seedlings developed resistance to infection by the third week after emergence, and roots were resistant at all ages. Hypocotyl rot strains were not pathogenic when tested against 14 agricultural hosts. Nine strains of F. oxysporum from agricultural hosts were not pathogenic when tested against P. lambertiana. Strains from Oregon ponderosa pine hypocotyl cankers were pathogenic on P. lambertiana hypocotyls.