Farm Forestry New Zealand

PESTS AND DISEASES OF FORESTRY IN NEW ZEALAND

dutch elm disease 1993-94

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.

DUTCH ELM DISEASE - ANOTHER SEASON ENDED
From Forest Health News No. 30, April 1994
Trees infected by Dutch elm disease were found in 10 locations during the 1993-94 season. The infected area contracted, trees infected during this season were found at Ponsonby (Western Park yet again), Remuera, Epsom, St Heliers, and Howick. No new infections were found on the North Shore, Pakuranga, or East Tamaki. By the end of the season 8847 beetles had been trapped, 17 of these (0.19%) were contaminated with Ophiostoma novo-ulmi. Over 12000 locations with elms were inspected three times, once before Christmas and twice after Christmas. Further surveys in selected areas to locate elms are planned for 1994.

(Lindsay Bulman)

DUTCH ELM DISEASE 1993-94
From Forest Health News No. 28, February 1994
Last year's work clearly showed that to be successful, the dutch elm disease eradication campaign needed a lot more money and manpower than could be supplied by the Ministry of Forestry (MOF) and the Forest Research Institute (FRI). The much intensified campaign this season is funded by additional substantial contributions from the Department of Conservation, Auckland City and Manukau City with smaller contributions from Waitakere City and North Shore City. MOF is responsible for the organisation of the operation and FRI for the trapping of Scolytus multistriatus and technical support.

Arborists were employed in the spring/early summer of this season on surveys to locate elm trees. Foot surveys were undertaken in areas which were judged to be high-risk from previous experience and surveys from the road were carried out in lower risk areas. As a result of these surveys, the number of recorded elm locations increased substantially, from 3800 to 12200.

DUTCH ELM DISEASE ERADICATION CAMPAIGN
From Forest Health News No. 26, November 1993
The survey of all known elms began in mid-November and, so far, no infected trees have been found. The survey to record elm locations should be finished by 10 December. It was expected that the location survey would be finished before the detection survey began, which would have made organisation easier, but there were a number of snags-dogs with sharp teeth, for one. Organisational problems have loomed large, therefore, but everyone concerned, Peter Tate and Lindsay Bulman in particular, have coped magnificently and the detection survey has progressed in an orderly manner. The first detection survey should be complete by Christmas and the second survey will follow from mid-January to the end of February 1994.

The maximum temperature rarely rose above 20°C in November in Auckland and the trap catches were quite low. Only two traps - Murvale Reserve and Te Kowhai Place -caught 15 beetles each and the rest yielded only single figure catches. Extra traps have been set up to track down the sources of the beetles at Murvale and Te Kowhai. None of the beetles were contaminated with Ophiostoma novo-ulmi.

(Peter Gadgil )

Dutch elm disease surveys
From Forest Health News No. 22, July 1993
During June and July I undertook a major planning exercise for the next Dutch elm disease season. To plan the eradication campaign we needed to know how many elms are located in Auckland (on both public and private land), how long it would take to locate and inspect these elms, and what it would cost. The survey strategy to locate elms was based on a mixture of street-by-street drive surveys, and foot surveys where every section within a designated area is walked. The allocation of survey types to various areas was based on findings from previous years, where infected trees or large beetle populations indicated an intensive walk-through survey was warranted. Other low risk areas were allocated drive-through surveys only.

The elm population was estimated used data collected during a walk-through survey at Cockle Bay last season, and known elm numbers in other intensively surveyed areas. At Cockle Bay, 57 elm locations were found after surveying 577 households (almost 1 household in 10 had one or more elms). In other areas where 3 drive-through surveys were carried out the percentage of households containing elms was over 8%. These data were extrapolated to other areas and it was estimated that the 4 Auckland cities have a combined total of 20,400 elm locations, and 29,500 elms at a ratio of 16:84 public to private.

From standard times calculated during the walk-through survey at Cockle Bay, it will take an estimated 481 mandays to walk the high risk areas and a further 252 mandays to drive the remaining areas. MOF are looking to contract trained arborists to do the work. For the routine inspections to detect diseased trees, it was estimated that a person could inspect 60 locations a day in areas with high elm density, reducing to 40 locations per day in areas with fewer elms. The routine inspection surveys were estimated to take 257 mandays to inspect every elm location once. The surveys to locate elms and two inspection surveys were estimated to cost just over $200,000 and use upwards of 20 people.

(Lindsay Bulman)

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