Statewide survey for streptomycin-resistant fire blight in orchards

Abstract

Streptomycin is the industry standard for managing fire blight on apples and pears. In 2002, streptomycin-resistance was confirmed in Wayne County and eradicated through prompt action. In October 2011, streptomycin-resistance was confirmed in four apple blocks in Wayne and Ontario Counties. We conducted a statewide survey in 2012 to locate and characterize any additional resistant bacterial populations. A total of 174 samples were collected. Erwinia amylovora was isolated from 129 of these and 15 of these isolates were resistant to streptomycin (11.6%). Preliminary phylogenetic results show that all streptomycin-resistant isolates carry the streptomycin resistance genes, strA and strB, on transposon Tn5393 which resides on the non-conjugative plasmid, pEa29, meaning that the isolates had to be spread physically. The survey found seven new locations in which resistant bacteria are present in Wayne, Ontario, Monroe, Orleans, and Niagara counties. These counties are now considered 'High Risk Areas' for streptomycin-resistant fire blight in 2013. To prepare for the 2013 growing season, we prepared new sample submission guidelines and fire blight best IPM practices for distribution by faculty and Extension educators, at the winter fruit schools, and at the Empire State Producers Ex