Phytophthora is a genus of parasitic microorganisms that cause a range of diseases in plants, particularly in the roots. The genus includes about 140 species. They are oomycetes, as are all water molds, and like other members of this group they have microscopic sporangia (spore capsules) that are produced in great numbers by germination of endospores. Certain conditions are more conducive to disease development, namely if the soil contains too much moisture and if the soil temperature is above 60 degrees Fahrenheit. In these conditions, oospores germinate and produce additional spores. These spores then infect a plant’s root and rot the system over time. More spores form in the residue, and the entire cycle repeats, infecting other plants.
What does Phytophthora Root Rot look like?
Some of the standard and most visible symptoms of Phytophthora root rot include the following:
- Leaves that turn dull green, yellow, or in some cases, red or purple
- Dark brown or black discoloration of the stem that extends up from the root/soil line
- General wilting of the leaves and branches
Other symptoms depend on the plant that is infected. Trees, for example, can have dark sap oozing from the trunk. Another symptom is reddish-brown streaks in the bark tissue. Signs of the disease can also appear on single leaves or branches of a tree and then spread to others.
Pine Tree
Arborvitae
Cryptomeria
