How to deal with European canker (Neonectria ditissima) in organic orchards (BIOFRUITNET Practice Abstract)

Summary

Less infected parts of the tree give a healthier tree and a better yield with improved quality.
Practical recommendation
Preventive measures
• Cultivar susceptibility differs. If fruit tree canker is known to be a problem in the orchard, choose less
susceptible varieties.
• Do not plant a new plot downwind of an old plot with a lot of fruit tree canker.
• Start with healthy trees and inspect the trees in the nursery.
• The type of soil and soil conditions influence the susceptibility of the trees. Plant the trees in healthy soil with good soil life. Avoid plots that are regularly flooded.
• The growing circumstances influence the susceptibility. Avoid dense trees, limit the growth with root pruning, and use limited fertilisation. The aim is to achieve balanced tree growth.
• Young trees with stem infections should be removed.
• Cut away infected spots on the stem and prune away infected branches. Repeated canker-pruning is
necessary: in autumn/winter, pre-flowering and after flowering, until the end of June.
• Avoid unnecessary wounds such as on stems along poles or caused by thread rubbing.
Direct measures
• Cover wounds in autumn with a wound sealer. This is only effective if the cankerous wounds have been cleanly excised/milled out.
• Copper sprays in autumn (when allowed in your country). Leaves treated with copper decompose worse. Therefore, apply other measures first. Use copper only when necessary.
• Lime water (calcium hydroxide) in autumn via spraying or via overhead irrigation. Calcium hydroxide is a basic substance in Europe.