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Preparation and Interpretation of Squash Mounts of Pseudothecia of Venturia inaequalis. David M. Gadoury, Graduate extension assistant, Department of Botany and Plant Pathology, University of New Hampshire, Durham 03824; William E. MacHardy, associate professor, Department of Botany and Plant Pathology, University of New Hampshire, Durham 03824. Phytopathology 72:92-95. Accepted for publication 26 March 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-92.

Management of apple scab requires information on the development of pseudothecia of Venturia inaequalis. One method often used to assess ascospore maturity and discharge is the examination of crushed pseudothecia. Previously described techniques for the preparation and interpretation of pseudothecial squash mounts have been based on the assumption that asci examined at various times in the spring represent the seasonís total production of asci. Results presented in this paper show that the number of asci per pseudothecium increases in early spring and then decreases in subsequent weeks. A new technique is described that used the maximum number of asci recorded per pseudothecium to correct for exclusion of undeveloped asci in early spring and exclusion of disintegrated asci in late spring. Corrected assessments more accurately depict the seasonal development of V. inaequalis and can be used to more accurately detect the depletion of the supply of ascospores.

Additional keywords: disease management.