Sudden decline of cabbage trees (Cordyline australis) in New Zealand

Rees-George et al.

Abstract

A sudden decline, followed by death, of mature cabbage trees (Cordyline australis) was first noted in the northern part of the North Island during 1987. The foliage turns yellow, and the oldest (lower) leaves wither and fall off. Growth of leaves ceases and eventually all the leaves fall, leaving dead branches often with the desiccated flowering panicles still attached. Trees are usually totally defoliated 4-6 months after the first symptoms appear. Concurrent with defoliation the bark on the trunk becomes loose and can be easily detached. Thirty-four locations between Whangarei in Northland and Gcraldine in South Canterbury have been surveyed for the incidence of sudden decline symptoms. The greatestnumberof dead trees(18-26%)wasrecorded around Auckland. Cabbage trees in the southern North Island and northern South Island were generally healthy with few dead branches and no symptoms of sudden decline. The cause of the disorder has notbeen determined. Fungi isolated from rotting roots and from branch tips of ailing trees were not considered to be primary pathogens. The possibility that cithcravirusoramollicuteis involved is under investigation.

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