If the bark on the branches of apple or pear trees discolours and bursts, fruit tree canker could be behind it. We show how to recognize and fight the dreaded disease.
In a nutshell
- common disease in apple and pear trees
- Rupture of the bark in disease
- bulging growths form, shoots die off
- Prevention and effective treatment possible
fruit tree cancer
Fruit tree canker is caused by the fungus Nectria galligena. It prefers to penetrate through wounds and cuts in fruit trees in damp, cool weather. Apple trees are mainly affected. The fungal disease occurs less frequently on pear trees.
The course of the disease occurs in several stages:
- Brown discolouration becomes visible on the areas affected by the fungus.
- The bark tears open.
- Concentric rings are formed.
- Lumpy growths form.
- Shoots above the damaged area die because the nutrient and water supply is impaired by the affected area.
Notice: Blossom and fruit rot on pear or apple trees can also be a result of infestation with the fungus Nectria galligena.
Fighting fruit tree canker
When fighting the fungal disease, it is important to act quickly. The further it can spread, the more serious the extent of the damage. If left untreated, it may be necessary to clear the entire tree.
Fruit tree canker on an apple tree
manual
Detect fruit tree canker
Check your apple and pear trees regularly for changes. Watch out for:
- discoloration of the bark
- torn spots
- Changes in flowers and fruits
- bulging growths at damaged areas
- drying branches
- Dying of individual shoots
Cut out small damaged areas
If you notice the typical brown-colored cracks and sores on your fruit tree early on, cut out these areas extensively. Use a clean, disinfected and sharp knife to remove the damaged areas down to the healthy wood. Treat the wound with wound care products.
Remove affected branches
If thinner branches are affected, remove them at least fifteen centimeters below the damaged area. Use wound sealants to speed healing.
Notice: To ensure that the tree can withstand the measures taken to combat fruit tree canker, choose a time between March and October for pruning. It is important that neither frost nor heavy rains are imminent. Mild, dry days are suitable.
Clear severely affected trees
If the infestation is severe and the tree is gradually dying, you will need to fell the tree to prevent it from spreading to other trees. A clear sign that a fruit tree is beyond salvage is a belt-like canker sore around the trunk. The fungus can spread and damage other trees, especially in larger, densely planted stands of trees.
Dispose of clippings safely
To prevent the harmful fungus from spreading, the cut branches and pieces of bark must be carefully destroyed. Dispose of them in household waste or in the organic waste bin. Alternatively, you can burn the tree cuttings.
Thoroughly clean tools
The stubborn fungus can survive on your tool for a long time. In this way, it can infect healthy trees during the annual fruit tree pruning. Cleanliness is an important measure to successfully fight cancer. Disinfect the tool carefully.
Notice: Only use sharp pruning tools for pruning fruit trees. Blunt scissors and knives cause injuries. These weaken the tree and form perfect entry points for fungi.
Prevention Tips
- For winter pruning, choose days with dry, mild weather.
- Protect fruit trees from frost cracking with a lime coat.
- Only use disinfected, sharp cutting tools for trimming.
- Check your trees regularly for changes.
- Avoid mechanical injuries to the trees when harvesting and mowing the lawn.
- Plant healthy varieties that are less susceptible to fruit tree canker
- Thin out apple and pear trees with dense crowns regularly.
- Ensure healthy, vigorous plants. Avoid stress caused by a lack of water or nutrients.
- Remove broken branches. These can provide an entry point for fungi and other pathogens.
- Fertilize wisely. Fruit trees that have been fertilized too much are more susceptible to fruit tree canker.
- Ensure good water drainage and avoid waterlogging.
- Plant an apple tree in a dry, airy spot. A suitable location is the best prerequisite for preventing disease and pest infestation.
frequently asked Questions
Does fruit tree canker only occur on fruit trees?No, deciduous trees such as alder, willow, poplar, ash and beech as well as walnut trees and holly are also attacked by the fungus (Nectria galligena). The disease is then referred to as tree canker.
When are fruit trees particularly at risk?After prolonged wet weather or long periods of frost, apple and pear trees are severely weakened and the fungus has an easier time of it. Only plant resistant varieties in rainy areas.
Are there apple or pear varieties that are particularly susceptible to fruit tree canker?The Klarapfel, Cox Orange, Elstar, Topaz, Gala Royal, Goldparmäne, Gloster and Berlepsch varieties are considered to be particularly endangered. Among the pear trees, the Williams Christ variety is susceptible to canker. When planting new plants, choose resistant species. Boskop and Pinova are affected less frequently.
Is fruit tree cancer also noticeable on the fruit?If a pear or apple tree is infested with the pustular fungus Nectria galligena, the flowers may die off and the fruit may change. The so-called calyx rot is noticeable in ripe fruits by brown discoloration around the stalk. The fungus spreads, and the fruit rots during storage. Destroy affected fruit carefully. They don't belong in the compost!