Nectria canker
Nectria canker, caused by the fungus Neonectria ditissima, is a serious disease that affects a wide range of hardwood trees. It is characterized by sunken, discolored lesions on the bark, which can girdle branches and trunks, leading to dieback and potentially tree death.
About this problem
Nectria canker is a fungal disease caused by Neonectria ditissima, which primarily affects hardwood trees. The fungus enters through wounds in the bark, often caused by pruning, frost, or insect damage. Once inside, it infects the cambium layer, disrupting the flow of nutrients and water. Over time, the cankers enlarge and may girdle branches or trunks, leading to dieback and, in severe cases, tree death. The disease is often confused with other canker diseases, but the presence of small, reddish fruiting bodies on the canker surface is a distinguishing feature. These fruiting bodies release spores that spread the infection to other parts of the tree and nearby plants.
Symptoms
- Sunken, discolored lesions on bark
- Reddish fruiting bodies on cankers
- Branch dieback
- Girdling of branches or trunks
- Tree death in severe cases
Cause
Nectria canker is caused by the fungus Neonectria ditissima. The disease typically takes hold when the fungus enters through wounds in the bark, which can be caused by pruning, frost, or insect damage.
Conditions that favour it
- High humidity
- Cool, wet weather
- Presence of wounds on trees
- Poor tree health
Lifecycle and spread
The fungus overwinters in cankers on infected trees. In spring and fall, it produces spores that are spread by rain, wind, or insects to new wounds on the same or nearby trees. Breaking the cycle involves removing and destroying infected branches and improving tree health to prevent new infections.
Plants most affected
- Apple
- Beech
- Maple
- Oak
- Birch
- Poplar
- Ash
- Elm
- Cherry
- Hawthorn
Treatment
Educational information only, and not a substitute for professional diagnosis. Identify the problem before treating it, and check that any product is registered for this plant and this use where you live.
Cultural control
- Prune trees during dry weather
- Avoid wounding trees
- Improve tree vigor through proper fertilization
- Ensure good air circulation around trees
Organic options
- Copper-based fungicides
- Neem oil
- Sulfur sprays
Chemical options
- Thiophanate-methyl Used to manage fungal infections
Read and follow the product label. The label is the legally binding instruction. Confirm the product is registered for this plant and for this use in your area before applying it.
Prevention
- Regularly inspect trees for signs of canker
- Prune out infected areas promptly
- Maintain tree health through proper care
- Avoid planting susceptible species in high-risk areas