Occurrence of Root Rot of Lettuce Caused by Fusarium oxysporum f. sp. lactucae in Hokkaido

Abstract

In 1997, root rot occurred on butter head lettuce (Lactuca sativa L.) cultivated at plastic-film houses in Asahikawa, Hokkaido. Diseased lettuce did not grow well and its outer leaves turned yellowish brown. Diseased primary root discolored in the vascular bundles, and its inner parts decayed. Causal fungus of this disease was identified as Fusarium oxysporum f. sp. lactucae from the pathogenicity and the morphological characteristics.