APS Abstract of Presentation

Occurrence of copper resistance in Xanthomonas axonopodis pv. citri in Argentina
B. I. Canteros (1), M. RYBAK (1), A. Gochez (1), P. Velazquez (3), M. Rivadeneira (5), M. Mitidieri (4), S. Garran (2), L. Zequeira (1)
(1) INTA, EEA Bella Vista, Ctes., Argentina; (2) INTA, EEA Concordia, Entre Rios, Argentina; (3) INTA, EEA Famailla, Tucuman, Argentina; (4) INTA, EEA San Pedro, Buenos Aires, Argentina; (5) INTA, EEA Yuto, Jujuy, Argentina
Phytopathology 98:S30

Copper resistance was detected for the first time in Argentina in 1994 after decades of citrus canker control with copper-containing bactericides. The addition of mancozeb to the copper products was recommended immediatelly. Since 1994 and till March 2008 we surveyed all citrus growing areas of Argentina taking samples of canker-affected tissue and testing the copper susceptibility of the isolated strains. Cu-resistant strains were those that grew on lima bean agar plus 200 ppm of copper sulfate and in water suspensions of bactericides containing 1.5 grams metallic copper per liter during 36 hours. Cu-susceptible strains died after 30 minutes in water plus Cu and grew in lima bean agar without copper and did not grow in solid medium with copper. A total of 3350 strains were rated, about 10% of them were Cu-R. The resistant strains were only from several groves in the NW of Corrientes Province from 1994, from one grove in Formosa in 2004, and from one grove in the SE of Corrientes in 2007. All the other strains from other groves located in Corrientes, Entre Ríos, Misiones, Formosa, Chaco, Buenos Aires, Tucumán, Salta, Jujuy, and Catamarca provinces were susceptible to copper containing bactericides. The early application of the mix of mancozeb to copper at least once a year was enough to stop or delay the occurrence of Cu resistant strains.