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Forest health update

Dean Satchell, New Zealand Tree Grower February 2012.


Needlecast has been quite bad over the past winter on radiata pine with many parts of the North Island affected and even around Nelson in the South Island. It has been sporadic and in many cases quite serious with members of the public asking what is killing the pines. It should firstly be understood that needlecast does not kill pines. Although the brown appearance looks bad, the trees do recover with new spring growth.

During the winter of 2008 needlecast was particularly prevalent in higher elevation areas in the North Island, notably Northland and East Cape. This winter I have seen symptoms appearing in Northland again, with what can only be described as a cryptic distribution. Symptoms appear worse nearer ridge tops, but while some stands are affected quite severely, adjacent stands may be unaffected.

Kaipara and Awhitu peninsula have had their share and it is quite obvious adjacent to State Highway 1 through the Brynderwyns. Glenbervie Forest near Whangarei has been hit worse than in 2008, yet much of the radiata throughout Northland remains healthy. It is not currently known what causes this needlecast and researchers at Scion are working hard at solving this.

As an industry should we continue to be putting all of our eggs in one basket with a focus on only one species? Or should we put sufficient resources into alternatives to be able to broaden our options?

Myrtle rust

This fungal rust disease, Puccinia psidii which is native to South America, has become established in Australia. It is considered ineradicable and is widespread. It affects plants in the myrtaceae family including eucalypts. The disease could be a significant threat to Australia’s ecosystems because 70 to 80 per cent of Australian native trees are myrtaceae.

The spores are spread easily by wind and with enough moisture, and the right temperature, bright yellow pustules occur, causing outer leaves and tips to become distorted and eventually die. Badly affected young plants can perish. The disease is likely to affect some species more than others but because severity is influenced by environmental conditions it will be some time before we will know the true effect of this disease in Australia.

MAF is carrying out readiness work here in New Zealand which includes developing a preparedness and response plan with stakeholders. Both native and exotic plants are at risk and it will only be a matter of time before it blows across the Tasman.

West Indian drywood termite

An infestation of the West Indian drywood termite Cryptotermes brevis in a residential house at Waikanae was reported to MAF in February 2011. This termite is considered one of the most damaging invasive drywood termites in the world. It is a threat to timber and houses built with wood.

The most likely pathway is that the termites were accidentally introduced by wooden items the homeowners brought from Peru 10 years ago. The house has been fumigated and eradication is the goal.

Kauri dieback

The Kauri dieback long term management programme to manage the effects of Phytophthora taxon agathis (PTA) on kauri trees has various projects underway. These include getting a more accurate view on the distribution of the disease as a priority.

Soil sampling is under way to determine the extent of detectable PTA throughout the natural range of kauri forests. The results will be used in determining the appropriate management of sites where PTA has been detected and to determine the extent of further surveillance.

There is a three year research programme to understand the ecology and pathology of the organism. The programme has an 0800 number 0800 NZ KAURI and a website which is updated regularly.

Dean Satchell is a member of the NZFFA National Executive and the NZFFA forest health representative

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