Woolly Apple Aphid
Eriosoma lanigerum is a reddish-purple aphid, 1 - 2 mm long, covered in dense white woolly wax it secretes for protection. It forms dense colonies on bark wounds, pruning cuts, and branch crotches aboveground, and on roots belowground. Root colonies cause the most serious long-term damage, forming knotty galls that disrupt water and nutrient uptake.
Symptoms to Look For
- Conspicuous patches of white, fluffy, cotton-like wool on bark, branch crotches, and pruning wounds
- Reddish-purple insects visible under the white wool when disturbed
- Sticky honeydew coating bark and leaves below colonies, with black sooty mould developing on it
- Knotty galls or swollen areas on the roots, visible when the soil around the base is loosened
- General decline, dieback of affected branches, or reduced vigour in heavily infested trees
Affected Plants
Organic Solutions
Direct Alcohol Application
Dab colonies directly with a cotton bud or cloth soaked in 70% isopropyl alcohol or surgical spirit. The alcohol penetrates the woolly wax coating and kills the aphids on contact. Most practical for small colonies on accessible bark. Recheck after 10 days and repeat.
Insecticidal Soap or Neem Spray
Mix a 2% castile soap solution or neem oil spray and apply directly onto colonies at high pressure using a sprayer. Work the spray under the white wool coating. Multiple applications 5 - 7 days apart are needed to catch newly hatched crawlers that emerge from eggs protected under the colony mass.
Encourage Parasitic Wasps
Aphelinus mali, a tiny parasitic wasp, is a specific natural enemy of woolly apple aphid and provides significant biological control where it is established. Plant dill, fennel, phacelia, and yarrow nearby to support beneficial wasp populations. Avoid broad-spectrum insecticides that kill these natural enemies.
Scrub Bark Colonies
For accessible colonies on smooth young bark, scrub directly with a stiff brush soaked in soapy water. Remove loose bark, pruning stubs, and rough surfaces where colonies establish. Follow with a soap or neem spray to kill any remaining insects.
Prevention
- Plant on woolly apple aphid-resistant rootstocks where available - MM.106 and MM.111 have moderate resistance and are widely available
- Prune cleanly and seal large wounds promptly - rough pruning cuts and old stubs are primary establishment sites for colonies
- Maintain a moat of bare soil around the trunk base rather than deep mulch directly against bark, which creates conditions where root colonies go unnoticed for longer
- Plant a diverse understorey of flowering herbs and perennials to sustain Aphelinus mali and other beneficial parasitic wasps year-round
Garden, by Willowbottom recommends only organic, wildlife-friendly solutions. No synthetic pesticides, no harmful chemicals - ever.