Farm Forestry New Zealand

PESTS AND DISEASES OF FORESTRY IN NEW ZEALAND

Update on nectria flute canker

Scion is the leading provider of forest-related knowledge in New Zealand
Formerly known as the Forest Research Institute, Scion has been a leader in research relating to forest health for over 50 years. The Rotorua-based Crown Research Institute continues to provide science that will protect all forests from damage caused by insect pests, pathogens and weeds. The information presented below arises from these research activities.

UPDATE ON NECTRIA FLUTE CANKER, Forest Health News 183, April 2008.
NECTRIA ECOLOGY PROGRAMME, Forest Health News 183, April 2008.
NECTRIA FOCUS GROUP MEETING, Forest Health News 183, April 2008.

UPDATE ON NECTRIA FLUTE CANKER, Forest Health News 183, April 2008.

Nectria flute canker is a disease of radiata pine found in the South Island from mid-Canterbury south. The disease usually expresses as stem malformation and stain. While infected trees are not directly killed by the flute canker, and generally exhibit a healthy crown, the disease can severely reduce wood quality. The fungus associated with this disease, Nectria fuckeliana, was first formally recorded in New Zealand in 1996, although it is likely to have been present for some years prior to this time.

N. fuckeliana is a Northern Hemisphere fungus which has been commonly recorded as a saprophyte or wound invader of species of Abies and Picea. The New Zealand record of this fungus is the first finding in the Southern Hemisphere and the first record of N. fuckeliana as a serious pathogen of a plantation species.

The Nectria Focus Group was established as a collaboration between the forest industry and research providers to oversee research projects related to understanding the epidemiology of N. fuckeliana and finding effective strategies to manage Nectria flute canker. The group meets annually and this year met in Dunedin. The meeting included updates on current research projects and plans for future research, some of which are summarised in this issue of Forest Health News.

NECTRIA ECOLOGY PROGRAMME, Forest Health News 183, April 2008.

Research within the Nectria ecology programme is progressing well. The principal aim of the programme is to increase our understanding of the ecology and epidemiology of Nectria fuckeliana, and it is hoped that this may lead to better management strategies for Nectria flute canker disease. In the last year, the programme has focussed on three specific areas of research: pathogen dispersal, pathogen infection mechanisms and pathogen survival in the host.

N. fuckeliana, like many other fungi, produces three different spore types. Of these, the sexual ascospores appear to be the most common in plantations and are likely to be the primary dispersal method. The fruitbodies, or perithecia, that produce these spores usually develop on trees 9-12 months after infection and development of flute cankers. These spores are dispersed by water and can survive for at least 12 months under very cold conditions (~ 4°C).

Field trials have shown that N. fuckeliana is able to use a variety of methods to enter and infect trees. These include entry through pruned branch stubs, deep sapwood wounds and shallow stem wounds. Recent work by Power and Ramsfield has also shown that N. fuckeliana can be present in unpruned, unwounded trees (see FH News 165 August 2006 and FH News 175 July 2007). This finding has lead to a series of new trials looking at branch crotches at potential infection sites. We eagerly await the results of these trials!

Recently Ministry of Agriculture and Forestry Operational Research funding allowed the opportunity to examine the survival on N. fuckeliana in living trees and woody debris on the forest floor. Results so far indicate that N. fuckeliana can survive in living trees up to 12 years following infection and can survive in woody debris on the forest floor for at least 16 months. This fundamental work on the ecology of N. fuckeliana has helped to explain some of the results obtained from operational trials and has contributed to improved management of radiata plantations in diseased prone regions.

Anna Hopkins

NECTRIA FOCUS GROUP MEETING, Forest Health News 183, April 2008.
There was robust discussion on future Nectria research during a recent Nectria Focus Group meeting in Dunedin. Interim results from the work on relating external symptoms with internal defect were received with great interest and the Group clearly supported further work in this area. As a result, two new proposals have been submitted to WQI Ltd. One research topic will focus on determining the relationship of visible fluting to internal damage for use with pre-harvest inventories while the second area will evaluate mature stems at the mill and relate external damage with sawn value recoveries, by assessing the Pruned Log Index and other criteria. Both of these studies will help determine the economic impact of Nectria.

Other areas of research focus included testing a range of silviculture strategies to answer questions such as: will a less aggressive pruning regime result in less disease? A proposal to fund a new silviculture trial that may answer some of those questions has been submitted to the Forest Biosecurity Research Council. In addition, a new trial set up to examine the influence of weather during and after pruning was established in April. The other area of research focus was genetics where the need to identify susceptible genotypes and then eliminate them from the planting programme in affected areas was recognised. It was agreed that genetics offered an opportunity for mitigation of disease, while acknowledging that it would not offer a solution in the short-term, nor result in complete elimination of loss. Some outcomes from the fundamental ecology work discussed above, such as determining the spore type and amount of inoculum most important for dispersal and successful infection, will be important for testing stock in the field.

This information is intended for general interest only. It is not intended to be a substitute for specific specialist advice on any matter and should not be relied on for that purpose. Scion will not be liable for any direct, indirect, incidental, special, consequential or exemplary damages, loss of profits, or any other intangible losses that result from using the information provided on this site.
(Scion is the trading name of the New Zealand Forest Research Institute Limited.)