Investigation of oak tree decline in the Auckland region

Abstract

Concern about the poor health of oak trees in Auckland was raised in 2001 An intensive investigation of oak trees showing symptoms of decline (twig and branch dieback epicormic growth trunk cankers bark loss and tree death) was conducted in the Auckland area during 2006 Disease symptoms on trees at 13 sites were documented and samples of leaves stems trunks roots and soil collected Soil samples were tested for the presence of soilborne fungi using baiting techniques Fungi and bacteria from plant tissues and soil were identified using either morphological characteristics biochemical testing or molecular techniques The investigation resulted in a range of fungi and bacteria being identified One fungus new to New Zealand was detected and several new host associations observed No particular organism was implicated as the cause of the oak decline but several fungi and bacteria were likely contributors to the tree decline and death in Auckland