Cabbage tree decline

Forest and Bird, Volume 23, Issue 1, 1 February 1992, Page 4

Cabbage tree decline

SCIENTISTS at the DSIR claim to have isolated the disease which is ravaging the cabbage tree, Cordyline australis. The team from the Mount Albert research centre led by Dr Ross Beaver and Dr Richard Forster has discovered the DNA of a bacterial organism classified as an MLO (micoplasma-like organism) in trees affected with sudden decline syndrome. There was a complete correlation between the incidence of MLO and trees suffering from sudden decline. It is thought to be the first time that an MLO disease has been isolated using DNA techniques. Sudden decline, first noted in 1987, is marked by a yellowing of the foliage and the loss of the oldest (lower) leaves. Trees usually lose all their leaves within six months of the appearance of the first symptoms. Beaver and Forster fear that 90 per cent of cabbage trees in the northern third of the North Island

could be dead within five years. There are also increasing occurrences of the syndrome further south. Other scientists claim, however, that the correlation by the research team does not prove a causal connection and that the syndrome is more likely to be the result of background environmental change such as increased ultraviolet radiation brought on by depletion of the ozone layer. The next step for the research team is to identify the agent responsible for carrying the disease and devise a biological control. One possible culprit is the Australian passion vine hopper, an insect whose numbers have built up considerably in the past two decades. The DSIR is also seeking more funding from government and private sources to continue the team’s work.