SUMMARY
The aim of this study was to find an alternative to chemical products used in the control of fire blight disease of rosaceous plants. In this work, essential oils of two Moroccan Artemisia species: Artemisia mesatlantica and Artemisia absinthium were screened for their antibacterial activity against Erwinia amylovora the causal agent of this disease. The EOs extraction was carried out by water distillation method in Clevenger- type apparatus and analyzed by gas Chromatography-Flame Ionization Detector (GC/FID) and by Gas Chromatography-Mass Spectrometry (GC/MS). The antibacterial activity of extracted EOs was tested in vitro based on the agar diffusion method and broth microdilution method and in vivo on detached immature pear fruits. The results revealed that the yields of extracted EOs were 1.25 and 0.58% respectively for A. mesatlantica and A. absinthium. The chemical composition analysis showed that investigated EOs were characterized with a high amount of ß-Thujone (40.42% for A. mesatlantica and 36.25% for A. absinthium). Both EOs have a similar MIC value (2.08%). A. absinthium EOs were found to be more effective than A. mesatlantica EOs since they show the lowest MBC. These results indicate that EOs of A. absinthium and A. mesatlantica contained compounds with antibacterial potential against Erwinia amylovora. In the bioassay test, the application of A. absinthium EOs on detached immature pear fruits infected by E. amylovora resulted in total suppression of disease severity. Such natural products may represent a sustainable alternative to the use of chemical pesticides.