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Etiology

Shasta Daisy Vascular Wilt Incited by Acremonium Strictum. A. R. Chase, Research assistant, Department of Plant Pathology, University of California, Riverside 92521, Present address of the senior author: Agricultural Research Center–Apopka, Route 3, Box 580, Apopka, FL 32703; Donald E. Munnecke, professor, Department of Plant Pathology, University of California, Riverside 92521. Phytopathology 70:834-838. Accepted for publication 14 February 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-834.

A new vascular wilt of the Shasta daisy (Chrysanthemum maxumum) in California was investigated. Symptoms included vascular browning, wilting, stunting, and unilateral chlorosis and necrosis of the lower leaves. Acremonium strictum was isolated consistently from the stems, roots, and occasionally petioles of diseased plants. Although rarely seen, hyphae and conidia were found in yellowed xylem vessels of diseased plants. Disease symptoms were reproduced in the greenhouse and the field, although these were not as severe as in naturally infected field stock. Symptom expression in the field was cyclic and correlated with the recovery of A. strictum from affected plants. The host had to be stressed by excessive soil moisture or by the onset of flowering to obtain symptoms comparable to those of field plants. The host range of A. strictum included monocotyledonous and dicotyledonous agricultural plants as well as several species of weeds.