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Influence of Dew Period and Temperature on Foliar Infection of Greenhouse-Grown Tomato by Colletotrichum coccodes

June 1998 , Volume 82 , Number  6
Pages  639 - 641

J. M. Byrne , Graduate Assistant , M. K. Hausbeck , Assistant Professor , C. Meloche , Former Undergraduate Research Assistant , and A. M. Jarosz , Associate Professor, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824

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Accepted for publication 14 March 1998.

Effects of temperature, duration of leaf wetness, and leaf position on foliar infection of greenhouse-grown tomato (cv. Bonnie Best) by Colletotrichum coccodes were determined by inoculating plants with C. coccodes (5.0 × 105 conidia per ml) and keeping them in a dew chamber for 0, 4, 8, 12, 16, 20, or 24 h of wetting at 15, 20, or 25°C. One week after inoculation, leaf disks were placed on the surface of an amended medium on which colonies of C. coccodes were compact and easily identified, and severity of infection was quantified after 4, 6, and 8 days. There was no infection of plants incubated at 15°C, while plants kept at 20 or 25°C had increasing numbers of colonies when leaf wetness duration was extended beyond 12 and 8 h, respectively. Leaf position had a significant effect, with leaves tending to increase in susceptibility as they age. After 24 h of leaf wetness at 25°C, the mean number of colonies per leaf disk from top, middle, and bottom leaves was 23.8, 29.0, and 34.0, respectively.

Additional keywords: anthracnose, fungal disease, semi-selective media, senescence

© 1998 The American Phytopathological Society