Woolly aphid: how to recognise and treat it

Pest

Woolly aphid — Photo: Abrahami, CC BY-SA 2.5, Wikimedia Commons

Symptoms

Fluffy white wax on the bark, in cracks and pruning wounds, hiding blackish-brown aphids.
Soft, lumpy swellings on shoots and branches where the colonies feed.
The swellings split in frost and let in apple canker.
Galls on the roots stunt the tree.

Organic treatment

Squash small colonies with your fingers as soon as you see them.
Spray horticultural oil or insecticidal soap to cover the colonies thoroughly; this gives partial control.
Put flower pots stuffed with hay in the tree as shelters for earwigs, which eat the aphids.

Chemical treatment

Spirotetramat on new growth before it hardens; follow the label dose and pre-harvest interval.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Prevention

Inspect apple trees often from spring onward to catch colonies early.
Avoid pyrethroid sprays, which kill the parasitic wasp Aphelinus mali and trigger outbreaks.
Replace badly infested trees with trees on resistant rootstocks M106 or M111.
Encourage ladybirds, hoverflies, lacewings and ground beetles.

Plants it affects

Sources

Figures checked against these sources.