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Poster: Biology & Disease Mgmt: Chemical Control


Monitoring Pennsylvania orchards for the presence of streptomycin resistant Erwinia amylovora.
H. LAUKAITIS (1), B. Lehman (2), K. Peter (2), M. Baer-Lehman (1) (1) Shippensburg University, U.S.A.; (2) Pennsylvania State University Fruit Research and Extension Center, U.S.A.

Within the last 40 years, streptomycin resistant strains of Erwinia amylovora have emerged in apple orchards throughout the United States. To date, resistant strains of E. amylovora have not been identified within Pennsylvania; however, they have been found within neighboring states such as New York, raising concerns of resistant strains soon surfacing in Pennsylvania orchards. The purpose of this study was to determine if streptomycin resistant strains are present in apple orchards located throughout Pennsylvania. In 2015, isolates were collected from grower submitted fire blight samples to the Pennsylvania State University Fruit Research and Extension Center in Biglerville, Pennsylvania. Initial identification was performed using Crosse Goodman specific media and apple inoculation. Erwinia identification was confirmed with direct colony PCR using primers specific to plasmid Ea29. Positive isolates were screened for resistance using a disk diffusion assay (100 μg/ml and 2500 μg ml of streptomycin sulfate respectively). Resistance was evaluated by observation of the presence or absence of a zone of inhibition. Of the samples processed to date, none have demonstrated streptomycin resistance. Screening is ongoing and any resistant isolates obtained will be further evaluated for the presence of plasmid mediated and chromosomal genes involved in resistance.