VIEW ARTICLE

Factors Affecting Release and Dissemination of Physalospora obtusa Spores in a New Hampshire Apple Orchard. J. Holmes, Graduate Research Assistant, New Hampshire Agricultural Experiment Station, Department of Botany, University of New Hampshire, Durham, New Hampshire 03824; A. E. Rich, Plant Pathologist, New Hampshire Agricultural Experiment Station, Department of Botany, University of New Hampshire, Durham, New Hampshire 03824. Phytopathology 60:1052-1054. Accepted for publication 14 February 1970. DOI: 10.1094/Phyto-60-1052.

Humidity and temp range within a 24-hr period affect the release of Physalospora obtusa spores. Most spore releases occurred between 6 and 16 C. A significant number of conidia were released from the pycnidia 1 week earlier in the spring than ascospores were released from the pseudo-perithecia. Pycnidia and pseudoperithecia also retained approximately 25% of their spores in the fall. Spore release was 13 times greater when rains occurred at night than during the daytime. Dissemination of P. obtusa spores was mainly by splashing rain. Windblown spores occurred only rarely in spore traps during 1967 and 1968. Spores can be disseminated by the ladybird beetle (Hippodamia convergens).