This root-rot complex has been confirmed on three Plant Clinic samples this season. It is caused by several fungal pathogens that invade when plants are grown in tight clay or poorly drained soils. These sites are fairly easy to detect this year because of excessive rain in most parts of the state. Injury from environmental stress such as freezing, heaving, wind, etc. can predispose plants to infection.
Infected plants exhibit a lack of vigor and productivity. Eventually the plants die or become unproductive. Roots washed of soil are black instead of a healthy white. Although most strawberry roots in early summer are brown to black on the surface, these same roots should be alive and white internally. Wash roots of suspect plants and break the roots to look at the internal color. Laboratory isolations from affected roots provided several fungal pathogens, none of which could be identified as the sole cause of this decline. For this reason, a field diagnosis based on washed roots and observed conditions may be as useful as a laboratory diagnosis.
Many fungi have been implicated in this disease complex, but treating the fungi does not cure the problem. As long as the site stress is present, the problem will continue. Abandon areas that are infected with black root rot, or rotate to a nonhost crop. Establish a strawberry bed in a new site with loose soil that provides good drainage away from the root zone. Planting strawberries in clay or in low spots in the field will lead to chronic problems.