Report for Community Services Committee December 11, 2000 Meeting

Elm Tree Update (M. Phair)

Report Summary

This report provides an update on the City’s elm tree program.

Previous Council/Committee Action

At the October 17, 2000 meeting of City Council, Councillor M. Phair made the following inquiry:

“I would like an updated report on Elm trees in Edmonton that includes:

1. Incidence of Dutch Elm Disease and beetles trapped.
2. Dothiorella fungus.
3. Research conducted on Elm trees at the University of Alberta.
4. Status of Dutch Elm Disease Prevention Program.
5. Planting of new Dutch Elm trees.

I would like this inquiry to return to the Community Services Committee.”

Report

1. To date there has been no incidence of Dutch Elm Disease (DED) in Edmonton. The only reported and confirmed incidence of DED in Alberta was discovered in Wainright in 1998 and confirmed in the spring of 1999. This appears to have been an isolated incident, as no further trees have been infected. Monitoring for the disease and the presence of beetles continues across the province. Three smaller European elm bark beetles have been found in Edmonton in 2000, compared to six in Edmonton and one in St. Albert in 1999 and 13 in 1998.
2. A late summer 2000 survey of areas of Edmonton with previous high incidences of elm wilt found 55 new wilt cases on American elms. Samples were submitted to Dr. Tewari’s Plant Pathology lab at the University of Alberta for identification. The first 18 of these new cases are all Dothiorella ulmi; the remainder await identification. The wilt disease distribution seems to show a correlation of cases with higher elm density. The vast majority of wilt cases are large roadside American elms.
3. Dr. Tewari has begun collecting DED specimen material for a reference collection at the University of Allberta plant pathology lab. This will assist with more rapid identification of DED should the disease gain a foothold here. This effort was supported by a research grant of $9500 from the International Society of Arboriculture. Little is known about Dothiorella ulmi. To date no funding has been obtained to enable research to determine how it spreads and the best way to control the disease. It is expected that fundraising efforts through the Society to Prevent DED will contribute $20,000 toward diagnostic tools for DED research in 2001-2002.
4. A multi-faceted DED prevention program continues in Edmonton. This includes elm bark beetle monitoring, elm wilt disease monitoring, intensified pruning of elm and enforcement of the DED bylaw. (Attachment 1)
5. For the first time since the discovery of DED in Winnipeg in 1975, successful management programs have re-established the American elm as a choice species for boulevard planting. In the past two years, 543 American and Brandon (an American/Siberian hybrid) elms have been planted along boulevards and in parks in Edmonton.

Background Information Attached

1. Status of DED Prevention Activities

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Attachment 1

Status of DED Prevention Activities

Third Quarter Report for 2000

C. Saunders, Edmonton Community Services

Elm Bark Beetle Monitoring:

In the greater Edmonton area, a total of 100 sites are currently being monitored for elm bark beetles using smaller European elm bark beetle (SEEBB) pheromone baited sticky traps. This has been reduced considerably from the 153 sites in 1999, largely through down-sizing of the City of Edmonton’s trap sites from 109 last year to 57 this year (see Table 1 below). These 57 Edmonton trap sites include 11 at tree nurseries.

This year only one Edmonton trap site (Newton) has been intensified with a denser distribution of sticky traps. In addition, the use of elm log traps has been abandoned altogether.

To date just three smaller European elm bark beetles were recovered to the end of August. Two were found at Kei Wanna kennels in south Edmonton, where a single SEEBB was found in 1997. The third was found in the Newton neighbourhood, where beetles were also trapped in 1996, 1998 and 1999. Monthly traps for the capital region for September have yet to be scanned. In addition, the first set of 90-day lure traps has been scanned with no elm bark beetle catches. The second set has largely still to be received for inspection.

Table 1: Greater Edmonton Monitoring Sites for Elm Bark Beetles.

Locality

Elm Wilt Disease Monitoring:

Following a late summer survey restricted to areas of Edmonton with previous heavy elm wilt expression, 55 new wilt cases on American elms were discovered and samples submitted to Dr. Tewari’s Plant Pathology lab at the University of Alberta for identification. The first 18 of these new cases are all Dothiorella ulmi; the remainder awaits identification. A review of wilt case distribution seems to show a correlation of cases with higher elm density. Again the vast majority of wilt cases are large roadside American elms.

Plans to initiate testing of the systemic fungicide, Alamo®, (propiconazole) to determine effectiveness against Dothiorella wilt were not carried out this year due to unsuccessful attempts to obtain funding from the Canadian Research Trust of the International Society of Arboriculture and Canada Trust’s Friends of the Environment Trust Fund. In addition, prior to their involvement in field trials, Engage Agro has requested some confirmatory trials to show efficacy of propiconazole on Dothiorella lab cultures. These trials are estimated to cost $600 for which funding is also required.

Elm Tree Removals:

In Edmonton, the overwhelming reason for removing elm trees is because of severe dieback associated with Dothiorella ulmi infection. In the last round of elm tree removals 15 of 24 removals were D. ulmi infected trees. Other elm mortality were attributed to single cases of Cytospora, and an unidentified fungus; a lightning strike case, and six undetermined pathologies, likely associated with weather-related stress.

Elm Inventory and Pruning Cycle:

In response to concerns over the discovery of elm bark beetles in Edmonton in 1995, and the segregation of elm pruning to the months of October through March, a new schedule of elm pruning was developed in 1996. Over the past three and a half years (up to the end of March 2000), intensive elm pruning has resulted in 82% of Edmonton’s city-owned elm trees being pruned. Edmonton elms are pruned every four years. Of noteworthy mention is the continued planning and tracking of elm maintenance activities on an electronic elm inventory system developed with HRDC funding.

Notable Stressors To Elm Trees:

Spring drought conditions in Edmonton this year prompted the very early appearance of salt stress symptoms, especially noticeable on centre median elms along major roadways. Whereas damage by the fall cankerworm and other elm defoliators has subsided this year, populations of a newer pest, the elm leaf miner, Fenusa ulmi, have increased tremendously this year in Edmonton. This pestwas first noticed in Edmonton in 1998.

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