Black root rot may be caused by several factors, known as a "disease complex." This complex is associated with a number of pathogenic soil fungi especially Rhizoctonia and Pythium species. The complex is also associated with root-infecting nematodes, nutrient deficiencies, fertilizer burn, pesticide injury, and environmental conditions which may include drought, winter injury to the root system, and the freezing or water logging of the soil or a combination of all these factors. Older plantings or replanted fields are affected.

Symptoms, Disease Cycle, and Management

Symptoms include an uneven "patchy" appearance in the strawberry bed. The first evidence of infection is the appearance of brown areas on the normally white or tan roots. Eventually, death of the feeder rootlets will result and the structural roots of the mother plant blacken and deteriorate. As the disease progresses, the entire root will break off when bent, leaving a short stub at the crown. Affected plants become stunted and produce few berries and runners.

The disease is generally associated with soil types of a high clay content; therefore, planting in well-drained soil is recommended. Soil compaction and excessive irrigation should be avoided. Mulching to decrease winter injury, purchasing disease-free plants, and rotating crops every 3 to 5 years may also be considerations in the control of black root rot.