What attacks elm: pests and diseases the sources name
A register of the fungus, the phytoplasma and the beetle that Canadian, British, Illinois and Morton Arboretum sources tie to elm: which elms each page names, where it is recorded, the season each source mentions, and where the full profile is.
Checked against the sources at the bottom of this page on October 9, 2026. Rules, fees and pay change: the source has the last word.
This page reports what the named sources say. It is not a diagnosis of any tree and does not say what should be done with one. Each row names its source, all read on October 9, 2026. Where this site has a full profile, the row links it, and the regulated status tables are on the linked pages and are not repeated here. Elms are covered species by species in tree species in the agency records, including American elm, slippery elm, rock elm and winged elm.
The register
| Agent | What the sources record |
|---|---|
| Dutch elm disease, Ophiostoma novo-ulmi and Ophiostoma ulmi. Full profile | Kind: Fungus, carried from tree to tree by elm bark beetles Hosts: The Canadian Food Inspection Agency says all American, rock and slippery elms are highly susceptible. Forest Research names English elm, field elm and wych elm as susceptible and says English elm has sustained the greatest losses because it is the preferred food of the beetles that spread the fungus, not because it is more susceptible. The Morton Arboretum says all native and European elms are susceptible and that lacebark elm and Siberian elm are highly resistant. Forest Research also names Zelkova as susceptible. Where and status: Forest Research says it occurs in all parts of the United Kingdom and also in continental Europe, North America and New Zealand, and that it is not reportable. The Canadian Food Inspection Agency lists regulated areas by province, and that list is on the Dutch elm disease profile. It records detections in 2025 in Edmonton and Saskatoon. Season: Forest Research says symptoms first appear in early summer, with clusters of leaves turning yellow and wilting. The Canadian agency says wilted upper-crown leaves curl and turn brown by late June or July and often stay on the tree into winter. |
| Elm yellows, Candidatus Phytoplasma ulmi. Full profile | Kind: Phytoplasma, a specialised form of bacteria; also called elm phloem necrosis Hosts: The University of Illinois Extension says American and red or slippery elm, three other elm species and some hybrid elms are susceptible. Forest Research says English elm can be affected, that wych elm has not been confirmed as a host, and that European elm species tend to be much less affected than American elm. Where and status: Forest Research lists it as not present in the United Kingdom and notifiable, and says it was found in 2013 on some elm plants imported into England in 2012, with eradication action taken and no evidence found of establishment. It says the disease has been found in Italy, France, Germany, the eastern United States and southern Ontario. Season: Illinois says leaf symptoms can occur any time during the summer, that spread by leafhoppers is believed to happen mainly in late summer and fall, and that symptoms take 3 to 10 months to show after infection, depending on tree size. |
| European elm bark beetle, Scolytus multistriatus. Full profile | Kind: Bark beetle Hosts: Natural Resources Canada says the main host is white or American elm and that all native and introduced elms in North America are attacked, with Japanese zelkova also named. It says the beetle causes little direct damage to healthy trees and that death of the tree is caused by the pathogen, not the beetle. Where and status: Native throughout Europe, introduced to North America, first found in Massachusetts in 1909 and in Ontario in 1946, and found from Nova Scotia to British Columbia. The page gives no regulated status. Season: Two generations a year in Canada and three farther south in the United States. Adults emerging in spring feed on twigs of healthy trees, and the beetles overwinter as larvae, pupae or sometimes adults under bark. |
How the sources describe the effects
The three agents form one chain. Natural Resources Canada says the spores of the Dutch elm disease fungus stick to adult beetles emerging from infected trees and are placed into healthy trees through the small feeding scars the adults make on twigs. Dying trees are then chosen for the next brood, which carries the spores on. The Morton Arboretum adds that the disease can also pass through root grafts between trees, and the Canadian Food Inspection Agency says the same. Forest Research says Dutch elm disease has killed tens of millions of elms in the United Kingdom, and that a dead English elm is often replaced by a thicket of young elms growing from the surviving roots, many of which are later infected once they are large enough for the beetles to find.
Elm yellows works differently. Forest Research says the phytoplasma attacks the inner bark in very susceptible elms and effectively girdles the tree, and lists yellowing, dwarfed and early-falling leaves, witches' brooms at twig tips and early bud opening as symptoms. It says elm yellows is easily confused with Dutch elm disease, and Illinois says the same. Forest Research adds that trees with Dutch elm disease die back and die rapidly, while elm yellows can cause symptoms that do not end in the death of the tree, and that laboratory testing is needed to confirm it. The Morton Arboretum likewise says only laboratory testing can confirm Dutch elm disease.
Profiles on this site
All three agents in the table have full profiles: Dutch elm disease, elm yellows and the European elm bark beetle. The sources read for this page name no other elm pest with enough separate facts for a row.
Who the sources say to report to
Forest Research says there is no requirement to report suspected Dutch elm disease to the plant health authorities in the United Kingdom, and says a diagnosis can be requested from its Tree Health Diagnostic and Advisory Service, which usually charges a fee. For elm yellows it asks for reports of suspected cases through TreeAlert. The Canadian Food Inspection Agency has an online form for reporting a sighting of Dutch elm disease and says a trained arborist may need to take branch samples to find out whether an elm is infected. The reporting offices for each country are on the report a pest in Canada and report a pest in the United Kingdom pages.
Sources
- Canadian Food Inspection Agency, Dutch elm disease page (modified June 16, 2026), read October 9, 2026
- Forest Research, Dutch elm disease (Ophiostoma novo-ulmi) page, read October 9, 2026
- Forest Research, Elm yellows (Candidatus Phytoplasma ulmi) page, read October 9, 2026
- University of Illinois Extension, Elm yellows (Plant Disease Selectors), read October 9, 2026
- Natural Resources Canada, European elm bark beetle fact sheet (revision 2026), read October 9, 2026
- The Morton Arboretum, Dutch elm disease, read October 9, 2026