Host Range, Specificity, and Biometrical Measurements of Leveillula taurica in California. J. C. Correll, Department of Plant Pathology, University of California, Berkeley 94720. T. R. Gordon, and V. J. Elliott. Department of Plant Pathology, University of California, Berkeley 94720. Plant Dis. 71:248-251. Accepted for publication 22 October 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0248.

Powdery mildew of tomato caused by Leveillula taurica (=Oidiopsis taurica) was found on tomato in all of the major tomato-growing regions of California during 1983–1985. In addition to tomato, the pathogen was found on four crop hosts (pepper, cotton, artichoke, and onion) and six weed species. The morphological characteristics of L. taurica were similar on all hosts and included endophytic mycelium, dimorphic conidia (pyriform and cylindrical), long and often branched conidiophores, and conidia borne singly or in short chains. Isolates from artichoke had both endophytic and epiphytic mycelium. Conidial size varied considerably among the isolates. The range of mean conidial measurements was 71.4–49.7 × 24.1–16.6 and 65.2–44.6 × 22.7–16.2 µm for the pyriform and cylindrical conidia, respectively. All isolates tested except the one from artichoke were able to infect tomato and apparently represent one physiological race of the pathogen.