Look for
Look forLong white, or occasionally blue-grey, waxy residues which look like cotton wool appear on the bark and branches especially around old pruning wounds. There may also be droplets of sticky, sugary honeydew on the bark which may become infected with black sooty mould. Cankers may also be present on aphid infested areas.
Plants affected
- Apple, pear, prunus, crab apple, pyracantha, cotoneaster, elm, hawthorn and mountain ash trees.
About Apple woolly aphid
- Adult aphids are up to 2mm long and elliptical in shape. They are pinkish-brown but their waxy coating gives them a white, woolly appearance.
- This species does not overwinter as eggs but as young, under loose bark, or in cracks in bark or surface roots.
- Young emerge in spring to re-establish the colony.
- Aphids can give birth to as many as five live young a day so rapidly produce large colonies.
- After a few generations, winged adults develop and move to new trees.
- Colonies will develop around cracks and wounds in trees, as well as new shoots.
- Feeding by apple woolly aphids will cause knobbly galls to form making the tree more susceptible to canker and other infections.
- Aphids feed on plant sap and excrete plant sugars as honeydew.
- Honeydew often covers the leaves of a plant and then becomes infested with unsightly black sooty moulds.
Treatment
Chemical
Products containing the following chemical ingredients are all effective on Apple woolly aphid
- Pyrethroids and Pyrethrin
Organic
- Check tree shoots and bark regularly for signs of woolly aphid.
- Scrub areas within easy reach with a brush and a bucket of soapy water.
- Spray infested areas with a firm jet of water to help reduce aphid numbers.
- Spray with natural fatty acids such as an insecticidal soap.
- The parasitic wasp Aphelinus mali will attack aphids above ground level.
- Aphid predators such as ladybirds, aphidoletes, hoverflies, and lacewing larvae can be encouraged by providing suitable overwintering sites and by growing flowers which attract them.
Prevention
- Regularly check plants for signs of infestation and deal with them as soon as they appear.
- Encourage natural enemies like ladybirds, hoverflies and lacewings to become established in the garden by planting daisy-like flowers, yellow flowers and in particular, the poached egg plant Limnanthes douglasii.
- Avoid using broad spectrum insecticides which will kill beneficial insects as well as aphids.
- Encourage insect-eating birds such as blue tits, by hanging feeders in winter and nest boxes in spring.
- If planting new apple trees, use rootstocks which are resistant to apple woolly aphid.
- Paint pruning wounds with a tree coating composition to help prevent infestations establishing.
