have a very large, old cabbage tree and it is shedding more than
the usual amount of leaves. There are about 10 or so 'heads' of
leaves, a couple of which are now stumps with no leaves at all and
have turned sort of spongy. There was a caterpillar type thing on
it a while ago, but I sprayed it and now the new shoots are coming
without holes in, so I think I have killed that particular bug.
It flowered in summer, and someone said the excessive shedding may
just be the time of year. I have heard of the dreaded 'cabbage tree
disease' could this be it?
it sounds as if your cabbage tree has the 'cabbage tree virus'.
There is little that can be done to save it. If you cut the cabbage
tree down to ground level there is a good chance it may regenerate.
The signs of the disease
are dieback, yellowing of old leaves, and the collapse of the crown.
The disease was first
noticed in the mid 1980s. There are several theories regarding the
rapid decline of cabbage trees. Some think that it is related to
the high UV light experienced in New Zealand.
One nurseryman comments
that in a nursery situation, if trees are well watered, fertilised
and flowers cut off, they stop dying. The same nurseryman also noticed
that trees are not dying in the South Island like they are in the
North Island because they have evolved under higher UV light.
Scientists have found
the presence of a parasitic bacteria, Candidatus Phytoplasma
australiense, which is believed to be spread by the Australian
Passionvine Hopper. Research shows that the disease is similar to
the yellow flax disease which lead to the collapse of New Zealand's
flourishing flax fibre industry early last century.
The good news it that
the disease is not spreading as rapidly as it was, and Landcare
Research and HortResearch scientists are looking at ways to manage
the disease long-term.
by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor
of Resource Management.
with permission from NZOOM Home and Garden content,
from the previous
The views expressed here are not necessarily those of the RNZIH