| Abstract: | ABSTRACT We evaluated effects of both physical and biological components of the environment on growth of Pantoea agglomerans on inoculated pear and apple blossoms and on spread of the bacterium to blossoms on non-inoculated trees. The center three rows of 0.35- to 0.5-ha blocks of four pear cultivars and four apple cultivars were sprayed with a suspension of streptomycin-resistant P. agglomerans strain C9-1S (C9-1S) at 20 to 60% and 60 to 90% bloom. Cultivars were chosen to create a sequence of continuous bloom from late March (d'Anjou pear) through mid-May (Red Rome apple). Each cultivar block was quartered into plots; two plots were treated twice with streptomycin sulfate near mid- and full bloom to suppress populations of indigenous bacterial epiphytes and the other two plots were treated with water. Colonization of blossoms by C9-1S and by indigenous bacterial epiphytes were monitored on inoculated trees and along transects of noninoculated trees. Immediately after spraying, C9-1S was detected principally on blossoms sampled from inoculated trees. As bloom progressed, trees up to 18 m from inoculated trees had high proportions of blossoms colonized by C9-1S. Streptomycin significantly (P
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