Woolly Apple Aphid


General Description

Hosts

Apple, pear, hawthorn, mountain ash, and cotoneaster.

Damage

Twigs and branches - Aphids colonize around wounds on scaffold limbs, on twigs and water sprouts. Colonies can also cause galls on twigs and the bark to crack. The wounds also provide sites for perennial canker disease pathogen infections and for the apple clearwing moth to lay eggs.

Fruit - Honeydew may drip on the fruit causing russet spots and blackened lenticels.

Roots - Feeding causes galls or swollen enlargements on roots, and heavy infestations can reduce growth or cause death of nursery stock. The root colonies on bearing trees cause re-infestations each year. Colonies can be a nuisance to pickers as the crushed aphid bodies stain skin and clothing.

Identification

Woolly apple aphids are reddish to brown in colour, up to 2 mm long and covered with a cottony-like white wax (Fig. 1). They do not infest leaves. When squashed they leave a red residue.

Figure 1. Woolly apple aphid colony. (BCMA)

 

Life History

Adults overwinter on the roots and in protected sites on the tree. In the spring young aphids crawl to new sites. There are several generations per year. Dispersal between trees occurs by wind and birds.

Monitoring

Inspect trees in August to see if infestation is general and severe enough to threaten fruit. No treatment thresholds have been established for woolly apple aphids. Begin monitoring in midsummer or earlier during mild winters.

Management

Biological Control

Several predators (lady beetles, syrphid flies, green lacewings, earwigs) and a parasite Aphelinus mali play an important role in woolly apple aphid control.

Cultural Control

Treat perennial cankers. Remove suckers in summer to eliminate a source of population development. Prune out water sprouts in August, paint large pruning cuts with commercial pruning paint to discourage aphid populations.

Chemical Control

See chemical control of apple aphid. Field reports indicate Assail and Admire do not provide satisfactory control of woolly apple aphid. Research from Washington State showed Movento provided satisfactory summer control of woolly apple aphid.