VIEW ARTICLE

Ecology and Epidemiology

Effects of Leaf Age and Inoculum Concentration on Infection of Sour Cherry by Coccomyces hiemalis. S. P. Eisensmith, Department of Botany and Plant Pathology and the Pesticide Research Center, Michigan State University, East Lansing 48824; T. M. Sjulin(2), A. L. Jones(3), and C. E. Cress(4). (2)Department of Horticulture, Michigan State University, East Lansing 48824; (3)Department of Botany and Plant Pathology and the Pesticide Research Center, Michigan State University, East Lansing 48824; (4)Department of Crop and Soil Sciences, Michigan State University, East Lansing 48824. Phytopathology 72:574-577. Accepted for publication 20 August 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-574.

Effects of leaf age and inoculum concentration on infection of Montmorency cherry by conidia of Coccomyces hiemalis were investigated in the greenhouse. With increasing leaf age from 5 to 36 days at inoculation, there was a linear decrease in the ln (log_c) of the number of leaf spot lesions per square centimeter of leaf area 11 days after inoculation with 10⁵ and 10⁶, but not 10⁴ spores per milliliter; with leaves from 35 to 70 days old, the decrease in ln lesions per square centimeter occurred only at 10⁶ spores per milliliter. No changes in the ln of numbers of lesions were observed in leaves inoculated at 103 to 126 days of age. Leaves expanded fully within 16 days of unfolding. Resistance did not increase in the same manner as leaf growth, but continued after growth was completed. With 1- to 32-day-old leaves, mean number of lesions per square centimeter of leaf at inoculation did not increase between 10² and 10⁴, increased approximately 10-fold between 10⁴ and 10⁵, and increased less than 10-fold between 10⁵ and 10⁶ spores per milliliter. Germination on water agar was reduced at 10⁶ spores per milliliter.