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Development of Latent Infections on Cranberry Leaves Inoculated with Botryosphaeria vaccinii. G. J. Weidemann, Department of Plant Pathology, University of Wisconsin, Madison 53706, Present address: Department of Plant Pathology, University of Arkansas, Fayetteville 72701; D. M. Boone, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 74:1041-1043. Accepted for publication 3 April 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-1041.

The range of dew period temperatures conducive to the establishment of latent leaf infections and the histopathological relationship of Botryosphaeria vaccinii to cranberry (Vaccinium macrocarpon) leaves were investigated in growth chamber tests with inoculated cuttings. Inoculated plants were placed in dew chambers at 16, 20, 24, 28, or 32 C for 72 hr then incubated at 20 or 28 C for 6 wk. Latent infections were established most often with a 28 C dew period followed by a 28 C incubation. Microscopic examination of inoculated leaves demonstrated conidial germination and appressorial development within 24 hr. Appressoria usually formed adjacent to germinating spores without prior germ tube elongation. Penetration pegs developed within 48- 72 hr after inoculation followed by the formation of dormant infection hyphae within the cuticle or between the cuticle and outer wall of the epidermis. No additional development was noted up to 2 wk after inoculation.

Additional keywords: Guignardia vaccinii.