Farm Forestry New Zealand

PESTS AND DISEASES OF FORESTRY IN NEW ZEALAND

Dutch elm disease 1991 - 1992

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.

From Forest Health News No. 8, April 1992.

The monitoring programme for the 1991-92 summer has ended. Fifteen infected trees were found in 11 locations this season. In 4 locations the new infections dearly resulted from root transmission of the fungus from neighbouring diseased trees which were detected last season. It is obviously important that isolation of the roots of diseased trees by trenching should be carried out to prevent this type of infection. There was an extension of the known infected area to the east; an infected tree was found in Pakuranga, about 10 km east of the previous record at St Kentigerns Prep School. There was a major contraction in the area infected last season; no infected trees were found on the North Shore or in Parnell and Glen Eden.

A total of 2271 beetles were caught in the 85 pheromone traps (8766 were caught in 1990-91). Four traps yielded one beetle each which was contaminated with C. ulmi (0.2% of the total catch). Two of these 4 traps (East Tamaki and Howick) were outside the infected area.

Nomenclatural note: The aggressive sub-group of the Dutch elm disease fungus Ceratocystis ulmi (Buisman) C. Moreau syn. Ophiostomo. ulmi (Buisman) Nannfeldt, has been named as a new species, Ophiostoma novo-ulmi Brasier, (Brasier, C.M. 1991, Mycopathologia 115: 151-161) to distinguish it from the non-aggressive form from which it differs in several important characters. The New Zealand isolates belong to the aggressive sub-group and our fungus should be more properly called Ophiostoma novo-ulmi rather than Ceratocystis ulmi . ( Peter Gadgil )
 

From Forest Health News No. 6, February 1992
Dutch elm disease:
Two more infected trees have been detected - both in Remuera. Contrary to expectations beetle numbers from the traps have continued to be fairly low - for the 4 weeks of February total numbers were 89, 45, 73 and 131.
 

From Forest Health News No. 5, January 1992
Dutch elm disease:
Thirteen infected trees have been felled this season to date - 4 at St Kentigerns Prep School in Remuera, 2 others in Remuera, 3 in Ponsonby, 2 in Epsom, 1 in Kohimarama and 1 (last week) in Pakuranga. The latter is the only one outside the known infected area. Seven of these trees are thought to have become infected through root grafts. When individuals in a group or line of trees are confirmed infected, it is recommended that trenches should be dug to destroy root connections with neighbouring trees. Beetles have been detected further afield than last year (Albany and Manukau) and the outer ring of pheromone traps has been extended to Orewa in the north and Manurewa to the south. Numbers trapped are increasing at the moment, indicating the emergence of the second generation. However only 3 of the 1606 beetles trapped and plated this season have been found to be carrying the fungus (one each at St Heliers, Remuera and Howick).
 

From Forest Health News No. 4, November 1991
Dutch Elm Disease
Scolytus multistriatus pheromone traps have been monitored weekly since the beginning of November. Beetles have been recovered from 10 of the 80 traps - a grand total of 31 beetles for the 5 week period.
Inspecting pheromone traps can be dangerous. John Bain was bitten by a dog and then sprained his ankle kicking it.

At the Dutch elm disease meeting on the 3rd December it was indicated that Caltex have shown considerable interest in sponsoring the eradication campaign. Does this mean that FHO vehicles will have to be repainted with signs stating "Sponsored by Caltex"?

To date samples from two wilty looking elm trees have been collected - these are still being processed in the laboratory. Another suspiciously thin crowned tree is located at Auckland Zoo. Cultures of Ceratocystis ulmi isolated from elms in Auckland have been infected with 'd²' factor virus at Forestry Commission Alice Holt Research Station in England and returned to New Zealand. We hope to Infiltrate this strain of C. ulmi which has markedly reduced virulence into the existing virulent population (only if the eradication attempt is officially deemed to have been unsuccessful).
 

From Forest Health News No. 3, October 1991
Update on Dutch Elm Disease
After the firewood scare Auckland to Gisborne, a letter was circulated to all known elm tree owners in the Auckland region, pointing out the dangers of felled elm wood. The response to this circular was good and we have as a result of information received located and destroyed a number of firewood caches, as well as removed a large abandoned felled tree.

At this stage of the year most of the Golden elms are approaching full leaf, but many of the large green European elms have yet to show much in the way of foliage initiation.

So far this season we have collected another 12 new locations for elm trees in the Auckland region.

John Bain trapped two Scolytus multistriatus beetles in Murvale reserve on 30 October.

(Dave Hayes )
 

From Monthly Report- Forest Health February 1990
Surveys for elm trees with Dutch elm disease have continued in Auckland with many members of the Forest Health Research Field participating. A further 3 trees with typical symptoms were discovered and isolations from affected material are being carried out at FRI. In addition elm firewood was destroyed at 3 different locations.
The DED survey teams were joined by 3 Australians from Melbourne during the last week of February. Australia has feared the introduction of Cemratocystis ulmi for many years and took the opportunity of obtaining some practical experience with the disease. Dr lan Pascoe who developed the Dutch elm disease contingency plan for Victoria was joined by Dr Peter Yau from Melbourne's Parks and Gardens Division, and Craig Vincent who works with a large firm of tree surgeons.

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.)