Ash Dieback and Dutch Elm Disease in Skåne
Two fungal diseases have permanently changed Skåne's tree stock over the past 30 years: ash dieback and Dutch elm disease. Both are incurable, both have killed thousands of trees, and both are still active. As a villa owner in Bjärred, Limhamn, Falsterbo or Skanör, there is a high chance you have affected trees right now.
Here is how to recognise the diseases, why they cannot be cured, and when you must fell the tree for safety.
Ash dieback, the most common today
What is it?
Ash dieback is caused by the fungus Hymenoscyphus fraxineus (formerly known as Chalara fraxinea). The disease originally comes from eastern Asia and first affected our ash (Fraxinus excelsior) in Poland around 1992. It reached Sweden in the early 2000s and has since spread northward.
In Skåne, over 80% of all ashes are affected. The disease spreads via airborne spores and can infect over long distances.
How do you recognise it?
Early symptoms (years 1-2 after infection):
- Wilted leaves on individual branches even when the rest of the tree is healthy
- Brown spots on leaves in late summer
- Lance-shaped cankers on small branches and at branch junctions, often orange-brown
Later symptoms (years 3-5):
- Dead top branches visible from a distance
- Vigorous water-shoot formation on trunk and large branches, a desperate attempt to compensate for the dead crown
- Dark, sunken cankers on the trunk
- Brown discolouration in sapwood at cuts
Clear collapse (years 5-8):
- More than 50% of the crown dead
- Branch fall and safety risk
- Possible root rot from the fungus reaching the root via trunk cankers
Can it be cured?
No. There is no working treatment. Research at SLU and European universities is ongoing, but no practical cure for individual trees exists.
Resistance: Estimated 1-5% of the population is genetically resistant and survives. It is not possible to predict which trees without observing them over 10+ years. Practically, you cannot count on your ash being one of the few survivors.
When should the ash be felled?
- More than 50% crown loss → felling recommended
- Large cankers on the trunk → felling, safety risk
- The tree threatens house, road, person → felling regardless of crown condition
- The tree is at the aesthetic centre of the lot and you want to replace it → felling, plant new species
You can let a diseased ash stand if there is no safety risk, many villa owners choose this while the tree still has a green side. But count on it having to come down within 2-5 years.
Dutch elm disease, more common in the 1980s but still active
What is it?
Dutch elm disease is caused by the fungus Ophiostoma novo-ulmi (and earlier O. ulmi). The disease spreads via the elm bark beetle (Scolytus laevis and S. multistriatus), a beetle that bores under bark and lays eggs there.
The disease arrived in Sweden during the 1980s and has since killed most of Skåne's elms. Wych elm (Ulmus glabra) has been hardest hit, the smooth-leaved elm (U. minor) is also affected.
How do you recognise it?
- Yellowing leaves in July, often on one side of the crown first
- Withered branches with brown leaves still attached into autumn
- Rapid spread through the crown over 1-3 years
- Brown discolouration in sapwood at cuts
- The elm bark beetle's traces under bark, small passages and holes
The disease moves fast. From first symptom to completely dead tree: 1-3 years.
Can it be cured?
No, treatment does not exist. Wych elm is effectively 100% lethal upon infection. The smooth-leaved elm shows some tolerance but often dies too.
Prevention for healthy elms: The area must be kept free of diseased trees that would otherwise spread the elm bark beetle. That is why diseased elms should be felled quickly and the wood destroyed correctly.
When should the elm be felled?
- Clear symptoms → felling recommended within the season
- To protect healthy elms in the neighbourhood → felling in autumn/winter (when the beetle is not actively spreading)
- Safety risk → felling regardless
Wood handling, extra important
The elm bark beetle lives under bark on diseased wood. If the wood is left untreated, the disease spreads further to healthy elms around.
We handle elm wood correctly:
- Chipping on site, entire tree including bark
- Haul-away to approved destruction facility (incineration)
- Never stacked as firewood outdoors, that is a source of spread
This is documented as needed for municipality or insurance.
Other tree diseases in Skåne
Honey fungus (Armillaria spp.)
Root parasite that affects many species (beech, oak, fruit, ornamental trees). Common after dry years since drought-stressed trees are more susceptible. Symptoms: yellow fruiting bodies at the trunk base in autumn, gradual weakening of the crown.
Fireblight on apple (Erwinia amylovora)
Bacterial disease that affects fruit trees, particularly apple and pear. Symptoms: leaves turn brown and wilt as if scorched, entire branches die quickly. Spread via cuts and insects. Can kill the entire tree in 1-2 seasons if not managed.
Horse-chestnut bleeding canker (Pseudomonas syringae pv. aesculi)
Affects horse chestnut. A bacterial disease causing dark, bleeding patches on the trunk and gradual crown decline. Very common in Skåne, much of the chestnut stand is affected.
How to avoid spreading diseases
As a villa owner in Skåne:
- Do not store diseased wood as firewood outdoors unless handled (especially applies to elm)
- Disinfect shears and saw between trees if pruning (alcohol or diluted bleach)
- Do not compost diseased leaves in a home compost (always to municipal composting with heat)
- Do not leave diseased wood in the chip truck or unhauled
We always follow hygiene protocols in our work and can document it for you.
Want an assessment of your trees?
Call +46 73 949 06 24 or write via the contact page. We come out, identify the disease, assess how urgent it is, and recommend action. Honest, local expertise throughout Skåne. Read more about our tree removal service, tree removal or pruning or tree removal in Limhamn (where ash dieback is particularly widespread).
