VIEW ARTICLE

Ecology and Epidemiology

Influence of Temperature and Wetness Duration on Infection of Immature and Mature Strawberry Fruit by Colletotrichum acutatum. L. L. Wilson, Research assistant I, Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH 44691; L. V. Madden, and M. A. Ellis. Associate professor, and professor, respectively, Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH 44691. Phytopathology 80:111-116. Accepted for publication 16 August 1989. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-111.

Immature and mature strawberry fruit were inoculated with a conidial suspension (2.5 × 10⁴ conidia/ml) of Colletotrichum acutatum and incubated under various wetness (free water) durations ranging from 0.5 to 51 hr at constant temperatures of 4, 6, 10, 15, 20, 25, 30, and 35 C. After drying, plants were moved to a greenhouse where incidence of fruit infection was recorded daily for 8 days. No infection occurred at 4 or 35 C on immature fruit or at 4 C on mature fruit. Generally, fruit disease incidence increased with increased wetness durations, but on mature fruit at 35 C, disease incidence decreased over time from a maximum of 39%. Optimum temperature for infection on both immature and mature fruit was between 25 and 30 C, with greater than 80% disease incidence after 13 hr of wetness. A regression model using the logit of disease incidence as the dependent variable accurately described infection level as a function of wetness duration (W) and temperature (T). Terms in the model were W, WT, WT², and WT³, and all estimated parameters were significant. Coefficients of determination for combined data from three repetitions of the experiment were 0.71 and 0.83 for immature and mature fruit, respectively.