A stem canker disease of olive (Olea europaea) in New Zealand

Abstract

A disease complex, with symptoms that include stem cankers and tip die-back, is reported in New Zealand olives (Olea europaea L.). Bacteria from stem cankers of olive were consistently isolated as pale lemon-yellow colonies on King’s medium B. On the basis of microbiological, molecular, and pathogenicity tests the bacterium isolated was identified as Xanthomonas sp. The bacterial isolates allowed verification of Koch’s postulates on young olive trees. As a result of our findings we suggest that the stem canker on olive is caused by Xanthomonas sp. In addition a fungus identified as Fusicoccum luteum was consistently isolated from stem cankers and tip die-back. In inoculated plants F. luteum occasionally formed cankerous symptoms though not as aggressively as Xanthomonas sp. At this stage it is not clear what role F. luteum has in primary infection.