Within tree and between tree spread of Ceratocystis fagacearum and implications for systemic chemical control

• Published in: Phytopathology 2005-06, Vol.95 (6)
• Main Authors: Blaedow, R A, Juzwik, J
• Format: Article
• Language: English
• Subjects: Ceratocystis; Ceratocystis fagacearum
• ISSN: 0031-949X

Much of our understanding of the movement of Ceratocystis fagacearum within infected oaks and between diseased and healthy trees is speculative. While histological studies have contributed to our understanding of pathogen growth, propagule transport, and host reactions within infected trees, questions with important implications for the chemical control of oak wilt remain. For instance, downward movement of the fungus following branch infection (as evidenced by symptom expression) throughout the tree via vegetative growth may take several months or years. However, observations of tree death in weeks to months following artificial inoculations in the crown suggest a more rapid means of spread may occur. Accelerated movement of the pathogen below ground has also been observed, and is attributed to the transpirational pull of viable propagules through the roots of a wilting tree across a root graft to a healthy tree. Systemic fungicides applied prior to or shortly after infection may halt downward movement of the fungus following branch infection, or prevent colonization by propagules that are rapidly carried upward from the roots. Such treatments may only delay the onset of symptom development if they are unable to eradicate the pathogen. A non-symptomatic but infected tree may then serve as a conduit for spread to adjacent oaks via the root system.