Woolly aphid

Eriosoma lanigerum

Crop: Apple

Why is it a problem?

Woolly aphids are a common pest of apple trees, causing damage to both the trees and the fruit. They feed by sucking sap from the tree, which can cause galls (swellings) on the roots and branches, weakening the tree and making it more susceptible to diseases. Galls can also cause splitting and secondary infections, and root galls can affect nutrient uptake.

Where and when is it a problem? It can cause problems in apple-growing regions.

IDENTIFICATION

Colonies are very characteristic, appearing as white woolly masses due to the covering of sticky, white wool. Colonies range in size from 2 mm to 6 cm.

SYMPTOMS

White woolly masses are easily visible on the bark, branches, and sometimes on the fruit. Galls and swelling may develop galls or swellings. Galls are most common on the roots, but in severe infestations, they can also be seen on branches. Galls can then split, providing entry points for disease. Woolly aphids excrete a sticky substance called honeydew, which can lead to the growth of sooty mold on the tree. Larger colonies weaken and stunt the growth of small trees. They can also reduce the formation of flower buds and subsequent fruit set in the following year.

Confusion with other pests: No other apple pests make white, woolly colonies.

BIOLOGY

Lifecycle: Woolly aphids overwinter in cracks, loose bark, and on exposed roots. They become active in March and April, and breeding colonies are established under the white sticky wool. Aphids occur on all parts of the plant (twigs, branches, and exposed roots). Part of the population remains on the ground throughout the year.

Dispersal: A few winged aphids are produced in June and July, which may infest other trees, but the most natural spread is by young wingless nymphs that crawl or are blown from tree to tree. Strict orchard hygiene is therefore important in limiting the unintentional spread of this pest.

When can damage be expected? Pest populations generally build up relatively slowly.

Hosts: In Bhutan, woolly aphids have only been reported on apple trees. It has many other hosts but is only known as a serious pest of apples.

MANAGEMENT PRACTICES

This is mainly a problem with young trees. The use of insecticide cover sprays should never be necessary, provided active monitoring and non-chemical management activities are undertaken.

Monitoring

  • Regularly inspect apple trees for signs of woolly aphid infestation, particularly during the growing season.
  • Aphids are a highly visible pest. Monitoring is needed, especially for young trees, which are most susceptible.
  • Use sticky traps to monitor aphid populations and the presence of natural predators.

Effect of variety

Not known.

Non-chemical management

  • For mild infestations, and infestations that can be reached by hand, aphids can be rubbed off with cloth soaked in a bucket of water and kerosene mix (or just water).
  • For large-scale mechanical control, colonies can be removed from the tree with the powerful jet from a power spray filled with plain water.
  • Suckers should be removed as they provide shelter for aphids.
  • Ensure good orchard hygiene practices are undertaken to minimize the spread of colonies within and between trees.

Chemical management

  • Except for treating infected seedlings, chemical spray is only needed in the case of severe infestations, which should not occur if monitoring and non-chemical management recommendations are being undertaken. While spraying, care should be taken to thoroughly soak the colonies as they are well protected by wax nurseries.
  • Chemical treatment of infected seedlings (where most serious damage occurs from gall formation in roots) is recommended before planting to prevent the further spread of this insect. The roots of these seedlings should be dipped in a solution of Chlorantraniliprole 18.5% SCĀ  before planting (0.3 ml per 1 liter of water).
  • The use of pesticide cover sprays should only be used as the last resort where non-chemical treatments are insufficient. The use of the systemic insecticide: Chlorantraniliprole 18.5% SC (0.3 ml per 1 liter of water) can be effective.
  • Application of Tree Spray Oil (30 ml of TSO in 1 liter of water OR 1 liter of TSO in 35 liters of water) in the winter to kill overwintering aphid colonies and eggs.

Version: NPPC 2017. Woolly aphid V1.0. Bhutan Pest Factsheet. www.PestsofBhutan.nppc.gov.bt. Date produced: 14 April 2017. Last date modified: 17 June 2024. Contact: nppcsemtokha@gmail.com

Image acknowledgements: NPPC.

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