TESTING THEORIES ON OVER-WINTERING TWIG BLIGHT, PRE-BLOOM DISEASE, SHOOT BLIGHT AND STEM INVASION

For fire blight risk assessment, a good understanding of the biology of the disease is needed. Concepts concerning the epidemiology of fire blight and migration routes of the pathogen in host tissues are working hypotheses. As such, they need continual reassessment and adjustment if necessary. This report describes the development of the author’s current concepts based on field observations in England, on published reports from other countries and on the results of experimental approaches. The epidemiology of blossom blight has been well described by others so the focus here is on late-season and pre-bloom infection risks and migration routes following infection. The report concludes with a list of working hypotheses, aimed at providing a basis for discussion and at encouraging further research in areas of uncertainty.