Annuals and herbaceous perennials transplanted into flower beds add color to many Kentucky landscapes. Unfortunately, when these plants fail to make good growth or die in the landscape, time and money are wasted and the anticipation of colorful splendor is lost.
Last summer, some beds of petunias, impatiens, vinca, geranium, begonia, and many other bedding plants died out due to one or more root and stem rot diseases. Most parts of Kentucky had excess rainfall in late spring and early summer last year, just after flower beds were established, thus contributing to loss of plants in the beds.
Root and stem rot pathogens, including Rhizoctonia, Thielaviopsis, Phytophthora, and Pythium were often involved, but sometimes abiotic influences made the disease problems worse. Although root rot fungi can be carried from the greenhouse to the landscape, some already living in the bed soil can attack healthy transplants.
Root rot is a general or localized root decay, whether from infectious or non-infectious causes or from natural aging. Root rot begins when cortical cells (outer tissue of the root) become non-functional or die.