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Survival of Xanthomonas campestris pv. citri in Citrus Plant Debris and Soil in Florida and Argentina. J. H. Graham, University of Florida, IFAS, Citrus Research and Education Center, Lake Alfred 33850. R. G. McGuire, and J. W. Miller. University of Florida, IFAS, Citrus Research and Education Center, Lake Alfred 33850, and Division of Plant Industry, Gainesville, FL 32602. Plant Dis. 71:1094-1098. Accepted for publication 16 July 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-1094.

Citrus nurseries infested with the Florida nursery strain of Xanthomonas campestris pv. citri (Xcc-FN) and dooryards and an orchard infested with the Asiatic strain (Xcc-A) were sampled to determine survival of the bacterium in soil and plant debris. Xanthomonads presumptively identified as X. campestris were recovered from nonsymptomatic plants and soil before and after eradication of citrus plants in nurseries but were not pathogenic to citrus. Pathogenic Xcc-A was detectable in leaf lesions of grapefruit and Pineapple sweet orange at least 90 days after defoliation under relatively dry conditions in the spring of 1986 in Florida. Under similar conditions in Argentina, Xcc-A was detected after 120 days in lesions of grapefruit leaves placed on the soil surface but only up to 85 days when leaves were buried. In air-dried sandy soil (1,500 cb soil water potential), Xcc-FN was detected up to 105 days, but under slightly moist to saturated conditions (70 to 0 cb), it survived for less than 24 days. Soil fumigants methyl bromide (MC2), methyl bromide-chloropicrin (6633%) (MC33), metam-sodium, and dichloropropene-methyl isothiocyanate killed citrus roots that otherwise resprout to produce susceptible host tissue. Metam-sodium and dichloropropene-methyl isothiocyanate were more effective than MC2 in reducing populations of Xcc-FN in grapefruit leaves, whereas MC33 had no effect on populations. In field trials in Argentina, MC2 and methyl isothiocyanate did not eradicate Xcc-A in lesions of grapefruit leaves but reduced the survival time in leaves from 85 days or more to less than 45 days.

Keyword(s): epiphytic survival.