Too many of our beloved cabbage trees – Tī kōuka – are hanging their heads (three relatively young trees in my street alone) in a rather sickly fashion, seemingly just weeks away from taking their last breath.
The fear that the once rural tree (now fashionably urban) could go the way of the dodo led us to contact Dr Ross Beever, Landcare Research’s celebrated scientist best known for his work leading the team that discovered the cause of Sudden Decline – the disease responsible for decimating large numbers of the cabbage tree.
“The culprit is a phytoplasma [specialised bacterium] called ‘Phytoplasma australiense’ carried by planthoppers [insects] which themselves get infected by feeding on infected plants; in most cases on karamu rather than cabbage trees,” Dr Beever said.
“The infected insects then fly to other plants – in the case of cabbage trees they collapse very rapidly. The incidence of Sudden Death is thus related to the number of infected planthoppers, which itself is linked to the number of infected karamu.
“The longer the tree has been around the higher the probability of it being infected – and thus we have lost/are losing many of the grand old trees.” He said it’s probable there is only one planthopper responsible – a native species called Oliarus oppositus.
Okay, Latin lesson over, but the take home message is there’s still no cure – let’s get planting. Both Greendoor Plant Centre on Havelock Road, and native tree specialists Titoki Nursery on Riverbend Road, Meanee, have good specimens of the endemic beauty available now.
I hope one day they’ll plant me in
The kind of hole they dig for horses
Under a hilltop cabbage tree
Not too far from the river that goes
Southwards to the always talking sea.
(James K. Baxter – “At Kuri Bush”, 1966)