Dogwood trees, with their colorful bracts and stately form, are welcome additions to the home landscape. Dogwoods are usually easy to grow, but sometimes they experience diseases that mar their beauty and health. One of the most serious dogwood ailments, phytophthora root rot, can kill a dogwood tree in a season.
Phytophthora root rot (Phytophthora cinnamomi) is a soil-borne fungal disease affecting dogwoods and other ornamental trees and shrubs. Phytophthora gains entry into the plant through injured root tissues, quickly spreading along lateral roots and up to the base of the trunk.
Dogwoods affected by phytophthora root rot develop browning along leaf edges, followed by leaf drop, branch dieback and general decline in plant health. Sometimes, the leaves turn yellow. The fungus can kill a tree in a season or two, though plants often linger for several years before succumbing, according to Bartlett Tree Research Laboratories.
Phytophthora enters dogwood roots when they are damaged during planting, grass cutting or digging. It can also enter wounds at the base of the trunk caused by lawn mowers or string trimmers. Dogwoods planted in soggy soils are especially vulnerable to phytophthora fungus.
There is no treatment for phytophthora root rot in the home landscape. Cut down affected trees, dig up the roots, and discard all plant parts in the local landfill. If a new dogwood is desired, plant one in another location. If an ornamental tree is needed for the same spot, plant a phytophthora-resistant species such as crepe myrtle or viburnum.
Prevent the introduction of phytophthora to your property. Never dig dogwoods from the wild or transplant them from another yard. Buy trees only from licensed garden centers known for stocking high quality plants. To prevent the spread of the fungus within the garden, clean tools after each use with disinfecting spray. Don’t mulch or compost any parts from diseased trees and don’t store any branches for firewood. Plant dogwoods in well-drained soil, raising the soil level a few inches to ensure good drainage.