Phytophthora Root and Collar Disease

A Technical Report from The Bartlett Tree Research Laboratories

Phytophthora root disease is a widespread but often overlooked disease of landscape plants. There are many species in this genus that attack woody ornamentals. These fungus-like organisms grow in the fine roots, cambium, and sapwood causing death of the tissue, root rot, and collar rot. Loss of water and nutrient absorbing capacity and stored carbohydrate reserves in the root cause a decline of the above-ground portion of the plant. Phytophthora diseases are most common on soils that are poorly drained or receive excessive irrigation. Phytophthora is a soil-borne organism that forms resting spores that can survive long periods without a host. When soil moisture and temperature conditions favor disease development, Phytophthora can increase rapidly from undetectable levels to infestations.