Wet winter weather leads to Taranaki’s pine trees turning red
Blame it on the rain.
A wetter than usual summer in Taranaki six months ago has contributed to large numbers of pine trees in the region taking on a reddish tinge.
The discolouring and defoliation is the result of the trees being infected by an algae called red needle cast, foresters say.
The disease is more apparent after long periods of wet, misty and cloudy weather conditions.
Red needle cast comes on the heels of myrtle rust which infected pohutukawa.
Taranaki Forestry Services manager Phil Bracegirdle said the disease was more widespread in pine blocks and plantations throughout Taranaki this winter than previous years.
‘‘We first noticed it three or four months ago and it is noticeable at Mangamahoe and as far south as Hawera,’’ he said.
Bracegirdle, who managed the Mangamahoe forest, said he had received calls from land owners.
‘‘It doesn’t kill the tree, unless it is under stress, but can temporarily stunt growth after the needles had fallen to the ground.
‘‘It seems to attack trees 10 years and older, not the younger ones,’’ he said.
‘‘The trees soon green-up again after losing the foliage and there is no long term damage to the wood.’’
Lindsay Bulman , a forestry pathologist for the Crown research institute Scion, said red needle cast affected both pines and Douglas-fir.
‘‘It is caused by a pathogen called phytophthora pluvialis which is native to the Pacific Northwest in United States. It is a fungus-like organism but more closely related to algae than fungi. It causes moderate to occasionally severe defoliation and outbreaks can be seen for a few months in years where there has been higher than average rainfall.’’
Bulman said the red needle cast had been in NZ since 2008.
The disease is more prevalent in central North island and East Cape but rare, or non existent in the rest of the country, he said.
‘‘In our experience the disease is patchy within a forest and generally occurred on sites that are prone to low cloud, or mist.’
Red needle cast outbreaks are normally followed by long periods of no disease outbreaks, he said.
‘‘It can show up over most of the year, but generally it occurs around March and can continue through to October.
‘‘The timing appears to be dependent on frequent wet or misty weather conditions, and so it varied considerably.’’
Bulman said the Rotorua-based forest research institute had received reports of red needle cast in Taranaki and the lower North Island, as far as Wellington.
‘‘It is also developing in some central North Island pine forests which we can relate to frequent and prolonged wet weather in affected areas.’’
The spores only affect live foliage and do not contaminate logs, but biosecurity issues were a major concern to the $1.7billion export log trade, he said.
Scion is working to develop a viable chemical control.