Recent Developments on Strawberry Plant Collapse Problems in California Caused by Fusarium and Macrophomina

Abstract

Beginning at least as early as 2005 and continuing through 2010, the California strawberry industry has suffered production losses caused by soilborne fungi not previously recognized as strawberry pathogens in California. The vast majority of these problems took place in fields that did not receive the traditional pre-plant fumigation treatment of methyl bromide + chloropicrin. These new disease developments have been consistently associated with two pathogens: Macrophomina phaseolina and Fusarium oxysporum f. sp. fragariae. Pathogenicity tests confirmed that these fungi caused symptoms similar to those observed in the field. Other experiments indicated that some strawberry cultivars are apparently less susceptible than others. Field trials using alternative fumigants provided some control of both diseases. In California, both Fusarium and Macrophomina are appearing in previously uninfested areas, indicating that these pathogens will be long-term concerns for this industry.