![]() After cutting away the outer bark, a sharp line of demarcation is commonly apparent between the healthy and diseased (orange-brown) tissue. Roots may be a dark brown or orange and may slough off from the primary root. Upon peeling back the outer bark of the trunk, the normally green cambium will appear orange or brown. When Phytophthora rots are suspected, inspect the base of the tree and excavate soil from around the trunk and root system to examine tissues for crown and root rot symptoms. Susceptible varieties may decline more quickly. Trees impacted by crown and root rot may appear to have a slow general decline that from a distance can be confused with winter injury, nutrient deficiency, fire blight, or wet feet (where saturated soils reduce the oxygen level to the point where roots die) (Figures1–4). citricola have also been isolated in Washington from symptomatic trees (Yamak et al. syringae two of the more significant species. Multiple species of Phytophthora have been implicated in crop damage with P. While generally considered a larger problem in rain-fed growing regions with heavy soils, Phytophthora problems occur in Washington, especially where irrigation water carries the pathogen or where irrigation and overhead cooling practices create wet soil conditions for extended periods. ![]() Phytophthora rots can girdle the scion (collar rot), damage the rootstock just below the soil surface (crown rot), and cause necrosis and death of fine roots (root rot).
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