Epiphytic Populations of Xanthomonas campestris pv. vesicatoria on Pepper: Relationships to Host-Plant Resistance and Exposure to Copper Sprays

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Abstract
Epiphytic populations of Xanthomonas campestris pv. vesicatoria were monitored on leaves and in buds of resistant and susceptible pepper cultivars over five seasons. Epiphytic populations were higher on the susceptible cultivar Jupiter than on the resistant cultivar Boynton Bell in four of the five seasons. In copper-sprayed plots, populations in buds of Jupiter plants were consistently higher than on leaves. In one test, copper sprays reduced X. campestris pv. vesicatoria populations by 99% on leaves, compared with only a 51% reduction in buds. In another test on a commercial pepper farm, no differences were found between populations on resistant and susceptible plants spaced as close as 1.2 m. However, combined data on buds for the three cultivars showed populations were higher than those on leaves on three of four sampling dates. These differences were attributed to the heavy use of copper on this farm.