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Phenological Analysis of Brown Rot Blossom Blight of Sweet Cherry Caused by Monilinia laxa. L. Tamm, Chr. E. Minder, and W. Flückiger. First and third authors: Institute for Applied Plant Biology, CH-4124 Schönenbuch, Switzerland; and second author: Department for Social and Preventive Medicine, CH-3012 Berne, Switzerland. Phytopathology 85:401-408. Accepted for publication 15 December 1994. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-401.

The influence of temperature and wetness duration on infection incidence of sweet cherry blossoms by Monilinia laxa was determined in controlled environment studies. Potted sweet cherry trees (cv. Star) were inoculated in full bloom (5 × 10(^3) conidia per milliliter), exposed to 0–24 h of wetness duration and incubated at temperatures between 5 and 20 C. The disease incidence increased with longer wetness duration and temperature within the range tested. A nonlinear model was used to describe the infection incidence as a function of temperature and wetness duration. Analytical tools were developed to determine a posteriori the infection date of blossoms observed in the field, based on the severity of the symptoms of the disease and the climatic conditions. A temperature-dependent physiological time was introduced to account for the influence of temperature on incubation period. An infected blossom passes through several macroscopically distinct stages of symptom severity. The characteristic change of the relative frequencies of the observed symptoms was used as a measure of the time that had elapsed since infection. The developed methods facilitate the analysis of field data in which the influence of climate, phenological stage of the host, and inoculum density on infection incidence can be elucidated.

Additional keywords: Prunus avium, epidemiology, stage-frequency matrix.