Symptoms of black root rot of strawberry are not often easy to detect. The plants exhibit a lack of vigor and productivity. When root systems are washed of soil, they show many black, rotted roots with only a few white feeder roots. Strawberry roots at this time of year are generally brown externally but should still be white internally. You may have to break a few roots to get a good idea of root health.
The black root rot complex is caused by a number of fungal pathogens that invade when plants are grown in tight clay or poorly drained soils. With this year’s abundant rains, these areas should be easy to spot. The disease can be initiated by environmental stress as well, especially winter freeze/thaw injury.
This disease cannot be identified any more certainly in the lab than in the field. Isolations from the roots would provide several fungal pathogens, none of which could be identified as the sole cause of this decline. Many fungi have been implicated in this disease complex, but treating the fungi does not cure the problem. In other words, chemicals are not recommended for black root rot of strawberry. As long as the site stress continues, the problem will exist.
If you have strawberries that have declined each year, including dead plants with roots as described above, consider establishing a strawberry bed in a new site. Make certain the soil is well drained and that water moves away from the planting bed. Planting on clay sites or in low spots in the field or garden causes chronic problems with strawberries.