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

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 microbiologic al, molecular, and pathogenicity tests the bacterium isolated was iden- tified as Xanthomonas sp. The bacterial isolates al- lowed 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.