Unthrifty growth of crown rot infected tree Photo by Janna Beckerman
Diagnosing Phytophthora crown rot is difficult. First examine the crown and rule out any type of mechanical damage, including rodent damage. Early symptoms of root and crown rot include delayed bud break, small leaves (often with leaf discoloration), and twig dieback. Bark discoloration, unthrifty growth, and premature leaf drop may occur later in the season (Fig. 2). Adding more nitrogen to trees symptomatic trees will actually worsen the problem!
Later symptoms, particularly for collar rot, often resemble rootstock blight, caused by the fire blight bacterium. Water-soaked, red-brown blight often extends throughout the susceptible tissue.
