Erwinia amylovora causes fire blight in economically important plants of the family Rosaceae. This bacterial pathogen spends part of its life cycle coping with starvation and other fluctuating environmental conditions. In many Gram-negative bacteria, starvation and other stress responses are regulated by the sigma factor RpoS. We obtained an E. amylovora rpoS mutant to explore the role of this gene in starvation responses and its potential implication in other processes not yet studied in this pathogen. Results showed that E. amylovora needs rpoS to develop normal starvation survival and viable but nonculturable (VBNC) responses. Furthermore, this gene contributed to stationary phase cross protection against oxidative, osmotic and acid stresses, and was essential for cross protection against heat shock, but non-essential against acid shock. RpoS also mediated regulation of motility, EPS synthesis and virulence in immature loquats, but not in pear plantlets, and contributed to E. amylovora survival in non-host tissues during incompatible interactions. Our results reveal some unique roles for the rpoS gene in E. amylovora, and provide new knowledge on the regulation of different processes related to its ecology, including survival in different environments and virulence in immature fruits.This article is protected by copyright. All rights reserved.