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Epidemiology of a Citrus Leaf-Spot Disease in Colima, Mexico. J. J. Stapleton, Department of Plant Pathology, University of California, Davis 95616; J. G. Garza-Lopez, SARH, INIFAP, CAETECO, Apartado Postal 88, Tecomán, Colima, Mexico. Phytopathology 78:440-443. Accepted for publication 13 October 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-440.

A leaf- and twig-spot disease (LSD) known as “bacteriosis” is a suspected form of citrus canker (Xanthomonas campestris pv. citri) that occurs primarily on Mexican lime (ML) trees (Citrus aurantifolia) along the central-Pacific coast of Mexico. Seasonal incidence and severity of presumptive LSD symptoms in two groves increased during the dry, cool months (November–May) and decreased during the warm, rainy season (June–October). Presumptive LSD symptoms were observed on all 15 citrus cultivars that were evaluated for natural infection in the field. Observed host susceptibility rankings showed C. limettioides, C. aurantifolia, C. macrophylla, and C. latifolia to be most susceptible to LSD, and C. sinensis ‘Valencia’, C. taiwanica, and C. reticulata to be least susceptible. C. sinensis ‘Washington navel’, C. grandis, C. aurantium, and C. paradisi were intermediate. Presumptive LSD symptoms could not be confirmed on varieties of Poncirus trifoliata. Natural symptom incidence of LSD on non-ML hosts decreased with increasing distance from ML blocks. No definitive X. c. pv. citri isolates were recovered during the course of these experiments, and epidemiological and etiological factors of LSD are unlike those of known forms of citrus canker.

Additional keywords: citrus disease, foliar disease.