Treatments with Non-Phytotoxic Concentrations of Cu and Mn and the Induction of Defence Mechanisms in Pear Trees against Infection with Erwinia amylovora

Abstract

Fire blight is a major threat to pear and apple production caused by the gram negative bacterium Erwinia amylovora. Pear trees were treated three times with metal solutions of Mn or Cu starting at the white bud stage. Subsequently, they were artificially infected with E. amylovora. Infection rates were assessed and ooze formation was monitored. At 7 days after infection, an inhibitory effect of Mn on the rate of infection could be seen. In a second trial, pear trees carrying young fruits were treated three times at 10-day intervals with Cu or Mn solutions. Chlorophyll fluorescence imaging analysis carried out one day post-treatment showed that the metal treatments do not cause phytotoxicity. The unripe fruit were harvested and artificially infected with fire blight. In this trial, a beneficial effect of the metal treatments on the infection rate or the ooze formation could not be demonstrated.