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Infection of Anjou Pear Fruit by Podosphaera leucotricha. R. A. Spotts, Associate Professor, Oregon State University, Mid-Columbia Experiment Station, Hood River 97031. . Plant Dis. 68:857-859. Accepted for publication 16 June 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-857.

A study was conducted to determine seasonal changes in susceptibility of Anjou pear fruit to infection by Podosphaera leucotricha, concentrations of airborne conidia during periods of fruit susceptibility, and sources of primary inoculum. Fruit infection first occurred when individual, unopened flowers were separating in the inflorescence and lasted about 6 wk, until petal fall. Mildew appeared 23 wk after inoculation. After mid-June, no fungal structures could be seen on infected fruit, and mildew russet was not clearly distinguishable from russet caused by pesticides or frost. Airborne conidia of P. leucotricha were first detected 4 days before or after full bloom, and concentrations were lower than 10/m3 during the period of fruit susceptibility. Shoots emerging from infected apple buds apparently constituted the source of inoculum.

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