Symptom Enhancement of Fusarium Wilt of Chrysanthemum by High Temperatures. Donna C. Gardiner, Former Graduate Research Assistant, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. R. K. Horst, and P. E. Nelson. Professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853, and Professor, Department of Plant Pathology, Fusarium Research Center, The Pennsylvania State University, University Park 16802. Plant Dis. 71:1106-1109. Accepted for publication 13 August 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-1106.

Chrysanthemum morifolium cvs. Royal Trophy, Mandalay, Glowing Mandalay, and Torch were inoculated with conidia of Fusarium oxysporum f. sp. chrysanthemi and grown under a 14-hr photoperiod at constant temperatures of 24, 27, 29, 32, or 35 C. Symptoms were rated on alternate days on a scale of 0 (no symptoms) to 5 (dead) for 28 days. Ratings were totaled for each cultivar at each temperature and divided by the number of inoculated plants to give an average total rating (ATR). The ATRs for Royal Trophy and Glowing Mandalay increased with temperature and were greatest at 35 C. The ATR for Torch was greatest at 29 C although there was no significant response to temperature. Symptomless plants of all cultivars were colonized by the pathogen. In vitro growth of the pathogen was not correlated with ATR and did not explain the observed responses.