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Dispersal and Management of Xanthomonas campestris pv. vesicatoria During Thinning of Direct-Seeded Tomato. Ken Pohronezny, University of Florida, Tropical Research and Education Center, Homestead 33031. Michael A. Moss, Wilbur Dankers, and James Schenk. University of Florida, Tropical Research and Education Center, Homestead 33031. Plant Dis. 74:800-805. Accepted for publication 16 May 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0800.

The spread of Xanthomonas campestris pv. vesicatoria during thinning of direct-seeded tomato was studied in two field experiments at Homestead, Florida. In a warm, humid season (spring 1988), the incidence of bacterial spot was less when plants were thinned in the afternoon when foliage was dry (44%) vs. those thinned in the morning when plants were laden with dew (87%). In a cool, dry season (fall 1988), disease incidence was reduced from 55% to 0% by waiting until afternoon when plants were dry before thinning. Ethanol and 10% povidone-iodine, applied as prophylactic hand washes, reduced disease incidence after thinning by 65% and 81%, respectively, in spring 1988. In fall 1988, no infected plants were detected when povidone-iodine was used; only 3.7% disease incidence was recorded for the ethanol treatment. In most cases, X. c. pv. vesicatoria could not be detected after hands were washed in either povidone-iodine or ethanol. Based on results of ordinary runs analysis of the distribution of diseased plants, the distribution of infected plants was generally highly clustered in all rows except those where bactericidal hand washes were used. Periodic hand disinfestation may be useful as a component of an integrated program for management of bacterial spot of tomato.