Dutch elm disease (DED) is a deadly vascular wilt disease that attacks almost all elm species where it is present (Ghelardini & Santini, 2009). Trees that become infected will gradually decline, first wilting (see below photo) and subsequently losing their leaves and becoming increasingly unable to carry out their normal biological functions. It is highly unlikely a tree will survive once it has caught DED.

The disease is caused by the fungus Ophiostoma novo-ulmi, which grows within the wood of the tree and is spread by the elm bark beetle (Scolytus multistriatus) that feeds on the wood, carrying the fungus with it as it moves from tree to tree.

 

First noticed in the Netherlands in 1910, DED soon spread across Western Europe before crossing the Atlantic Ocean and reaching the USA in 1928. Since then, it has killed hundreds of millions of elm trees (Ganley & Bulman, 2016) and cost billions of dollars in tree removals and other economic costs (Strobel & Lanier, 1981). DED was first found in New Zealand in December 1989 in a public park in central Auckland. An eradication programme was initiated by the Ministry of Forestry, but the funding was not sufficient to reach its goal. An estimated $4 million was spent, but this only managed to slow the spread of the disease. In 2008 the programme was stopped entirely, and responsibility was shifted to local authorities. Over the next decade, Auckland Council ran its own DED programme surveying elm trees for signs of infection and removing infected council-owned trees. A beetle trapping programme was employed on the Auckland-Waikato border, and in December 2021, DED was located in the Waikato region for the first time.

 

Since then the Waikato District Council has employed SPS Biota to deploy and survey a beetle trap matrix and conduct surveillance of elm sites within the Waikato Region.  Unfortunately multiple sites of DED infected elms have been found within the Waikato region, with work being undertaken as far south as Huntly.

 

It has been estimated that if Dutch elm disease continues to spread, over 90% of all elm trees in the country will die, costing councils and the public over $350 million dollars (Ganley & Bulman, 2016). While the costs of managing this disease may be high, it is clear that the price of doing nothing will be higher still. If the disease is not controlled in the Waikato region it will undoubtedly spread further and cover the North Island, and there will come a point where it is impossible to control. We need to act fast if we want to have any hope of saving our elm trees and avoiding the cost of their demise.

 

If you suspect you have DED please contact us on 0800 246 821 or email us admin@spsbiota.co.nz

 

 

References

Ganley, R. J., & Bulman, L. S. (2016). Dutch elm disease in New Zealand: impacts from eradication and management programmes. Plant Pathology, 65(7), 1047-1055.

Ghelardini, L., & Santini, A. (2009). Avoidance by early flushing: a new perspective on Dutch elm disease research. iForest-Biogeosciences and Forestry, 2(4), 143.

Strobel, G. A., & Lanier, G. N. (1981). Dutch elm disease. Scientific American, 245(2), 56-67.