Changes in the Sensitivity of Erwinia amylovora Populations to Streptomycin and Oxolinic Acid in Israel.

A survey of streptomycin resistance in the fire blight pathogen, Erwinia amylovora, conducted in pear, apple, and quince orchards in Israel during 1998 to 2001 revealed a decrease in the frequency of locations with streptomycin-resistant strains, from 57% in 1998 to 15% in 2001. In 2001, streptomycin-resistant strains were detected in only five locations in two restricted areas in western Galilee and the Golan Heights, compared with 16 locations found in 1998 throughout the northern part of the country. Since the use of streptomycin for fire blight control was terminated in 1997, this antibiotic has been replaced with oxolinic acid (Starner) in commercial orchards. Strains resistant to oxolinic acid were isolated from two pear orchards in the northern part of Israel in 1999. In a nationwide survey conducted during the spring and winter of 2000 and 2001, 51 and 47 pome fruit orchards, respectively, were sampled. Oxolinic acid-resistant strains were detected in several orchards located in two restricted areas in northern Galilee. Strains with resistance to both streptomycin and oxolinic acid were not found during 2000 to 2001. Results of this survey are used in managing fire blight with bactericides.