Phytophthora Root Rot Disease

Phytophthora is Greek for “plant destroyer.” The name is fitting for this soil-borne fungal disease which causes seed rots, pre- and post-emergence damping off of seedlings, and stem rot of plants.
Phytophthora species are microscopic organisms that primarily thrive in heavy or waterlogged soils and spread through splashing rain, irrigation water, and runoff water. They can spread through contaminated soil and gardening tools and equipment as well. Susceptible tree and shrubs species include, but are not limited to:

• Azalea
• Boxwood
• Conifers
• Dogwood
• Daphne
• Holly
• Juniper
• Taxus
• Rhododendron

Symptoms

Though there are above-ground symptoms that you can catch with the naked eye, these signs do not develop until the root decay is in its advanced stages. Such symptoms include wilting, yellowing or sparse foliage, and branch dieback. These symptoms will get progressively worse until the plant dies. For example, the foliage of infected conifers will fade from a vibrant to a dull green, eventually dimming out at brown.

Because the Phytophthora species are microscopic, there will be no evidence of the pathogen itself. Below-ground examination of the roots, however, will reveal a poor root system. The fine, feeder roots will have rotted and even the larger roots can turn brown or black internally. These roots will be softer than usual and break easily.