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Factors Affecting Sporulation and Infection by the Blueberry Stem Canker Fungus, Botryosphaeria corticis. R. D. Milholland, Associate Professor of Plant Pathology, North Carolina State University, Raleigh 27607; Phytopathology 62:137-139. Accepted for publication 10 August 1971. DOI: 10.1094/Phyto-62-137.

Temperature affects both the number and type of stem canker lesions produced by Botryosphaeria corticis on blueberry. The cultivar Wolcott was susceptible to B. corticis at 27 C, but showed a resistant reaction at 16 and 21 C. The resistance of the cultivar Bluecrop was not affected by temperature. The optimum temperature for fungal growth, sporulation, and spore germination was 27 C. No growth occurred at 10 C. Cultures of four races of B. corticis failed to sporulate when maintained in the dark. Light intensities ranging from 60 to 960 ft-c induced fertile pycnidia. Sporulation was optimum for all races when cultures were grown under 480 ft-c of light. A minimum of 6 days of continuous light at 480 ft-c was necessary to induce sporulation. Cultures grown for 8 days under light and 6 days in the dark produced more spores than those grown for 14 days under continuous light. A single 24-hr exposure to light during different phases of growth was not sufficient to produce fertile pycnidia.

Additional keywords: canker resistant, pycnidia production.