Preventive and indirect measures to regulate woolly apple aphid in organic orchards (Biofruitnet Practice Abstract)

Summary

A combination of preventive measures and promoting beneficial insects also enhances biodiversity in orchards and has positive effects against other pests, such as other aphid species.
Practical recommendation
Preventive measures:
• Avoid strong shoot growth by applying root pruning and summer pruning.
• E. lanigerum settles preferentially on wounds: Preferably, prune only some big shoots instead of many small ones. This will decrease the amount of cutting wounds that can fit as nesting aid.
• Keep the crowns of the trees airy so they can dry off quickly.
Indirect measures:
• Check for sensibility varieties/robust rootstock
• Organic orchards offer numerous natural antagonists for the woolly apple aphid. The parasitoid wasp Aphelinus mali and Earwigs (Forficula auricularia L.) are the most important ones. Further antagonists are hoverflies (Syrphidae), lacewing larvae (Chrysopidae carnea) and ladybugs (Coccinellidae septempunctata, A. bipunctata).
• Regulation with natural antagonists:
o Implement edge structures that encourage beneficial insects: Flower strips, hedges, etc.
o Implement alternating mulching.
o Install clay pots as nesting aids for earwigs.
o Distribute Aphelinus mali actively: Cut out well-parasitized woolly apple aphid colonies in fall, store them cool until spring, and then apply them selectively to affected orchards.
Direct control: Treating with a mixture of oil and sulphur at the bud break stage.