Plant Doctor Archive

Diseased cabbage trees

I have just read your reply to another question describing the 'dreaded cabbage tree virus'. I have four plants of varying ages within a garden of a lot of cabbage trees that are showing the same symptons — yellow leaves, drooping crown and mouldy brown areas. How can I stop this spreading to my other trees and how far back should I cut the sick ones? All the way to the ground seems drastic! (Do I have to paint the tops if I do this?)

Unfortunately it does sound like your cabbage trees may have the cabbage tree "sudden decline" disease. I asked Dr Ross Beever, of Landcare Research, what the latest was regarding the disease (Ross leads the team researching the disease).

The disease is not caused by a virus but by a specialised bacterium called Phytoplasma australiense and is probably transmitted by a sap sucking insect vector (possibly the passion vine leaf hopper).

In response to your question about cutting the sick trunks back, Ross says that it usually doesn't work, but occasionally you can be lucky. You often get re-sprouts which collapse and die after reaching a metre or so in height — they get the disease because they are connected to the infected rhizome under the ground. If the rhizomes are not connected, then you may be OK.

Advice by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor of Resource Management.

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