Sensitivity of Erwinia amylovora in Illinois apple orchards to streptomycin, kasugamycin, and copper
A. G. Jurgens (1), M. BABADOOST (2). (1) Dow AgroSciences, Gibson City, IL, U.S.A.; (2) University of Illinois, Urbana, IL, U.S.A.
Streptomycin and copper are widely used to manage fire blight, caused by <i>Erwinia amylovora</i>, in commercial apple orchards in Illinois. Statewide surveys were conducted in 2010, 2011, and 2012, and 117, 129, and 170, <i>E. amylovora</i> isolates were collected, respectively, from 20 counties, to determine sensitivity of <i>E. amylovora</i> to streptomycin, copper, and other antibiotics. None of the 416 <i>E. amylovora</i> isolates tested were resistant to streptomycin (Agrimycin 17WP) at 50 mg/L. Seven non-<i>E. amylovora</i> bacterial isolates were collected from blossoms and <i>E. amylovora</i>-infected shoots that contained both a strA-strB streptomycin-resistance gene and IS1133 on transposon Tn5393. Colony development of all 84 <i>E. amylovora</i> isolates tested were inhibited on Luria-Bertani medium amended with oxytetracyline (Mycoshield) at 50 mg/L and kasugamycin (Kasumin 2L) at 100 mg/L. Similarly, colony development of the 84 <i>E. amylovora</i> isolates was inhibited on the casitone-yeast extract medium amended with copper sulfate (Cuprofix Ultra 40DF) at 0.16 mM. In 2011 and 2012, field trials were conducted to evaluate efficacy of oxytetracyline (Mycoshield), kasugamycin (Kasumin 2L and ARY-0416-06), copper hydroxide (Kocide-3000 41.6DF), <i>Bacillus subtilis</i> (Serenade Max, QST713), and <i>Pseudomonas fluorescens</i> (Blight Ban A506) for management of fire blight in an apple orchard. Only kasugamycin (Kasumin 2L and ARY-4016-06) reduced blossom and shoot infection significantly.
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