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Green apple aphid (Aphis pomi Degeer)

Green apple aphid

Green apple aphid is a common but minor pest of apple, which also attacks pear. It is most important on young trees.  As the name implies it is bright green in colour and readily distinguished from other aphid pests of apple.

The life cycle starts when the aphid hatches in April at green cluster from overwintered eggs on the bark but the spring colonies that develop in shoot tips are of little importance.

Winged forms develop in summer, which migrate to the growing shoots of other apple trees.

Large, dense colonies develop along the lengths of the shoots from these migrants in summer and it is these that are damaging. The colonies have a strong distinctive smell.

Fruits in the vicinity of and below colonies become heavily contaminated with honeydew which becomes blackened by sooty mould and cast aphid skins. The colonies are usually attended by black ants.

The severity of infestation by green apple aphid should be determined in each orchard when pest assessments are done from late June to the end of August. Application of an insecticide to control green apple aphid should be considered if more than 10% of shoots have infestations causing leaf curling.

Control  

Many insecticides are approved for control of aphids on apple but if aphids are the only pests that need to be controlled, flonicamid (Mainman) is the preferred choice in conventional orchards as it is selective and partially systemic.

  • The neonicotinoids acetamiprid (Gazelle) and thiacloprid (Calypso) are also highly effective. They will also control various other pests such as mussel scale. Thiacloprid (Calypso) is considered to have some activity against codling moth. However, possible side effects on natural enemies including earwigs should be considered.
  • Use of synthetic pyrethroids, which are harmful to natural enemies, should be avoided.
  • An emergency authorisation for Movento Top for control of woolly aphid (which lasts until 29 August, 2017) will provide incidental control of green apple aphid.

 

Insecticides approved for use on apple which are recommended to control green apple aphid or offer some incidental control when applied to control other pests or diseases

Choice of insecticides – efficacy factors

Active ingredient Trade name (examples) Class Selectivity Approved for control of Safety to Typhs 
acetamiprid Gazelle neonicotinoid broad-spectrum, systemic Aphids and Whitefly safe
deltamethrin Decis etc. pyrethroid broad spectrum Aphids, apple sucker, capsids, caterpillars, codling & tortrix moths, sawfly harmful
dodecylphenol ethoxylate Agri 50E physical acting insecticide broad spectrum Aphids, leafhoppers, mealy bugs, spider mites harmful
fatty acids Savona soap broadspectrum Aphids, scale insects, leafhoppers harmful
flonicamid Mainman neonicotinoid selective Aphids and woolly aphid safe
maltodextrin Majestik polysaccharide broad spectrum Aphids, spider mites harmful
pyrethrins Spruzit Extract from pyrethrum broad spectrum Aphids, apple blossom weevil, caterpillars, scale insects, spider mites harmful
spirotetramat (120-day authorisation which lasts until 29/08/17) Movento Top tetramic acid derivative selective Woolly aphid unclassified
thiacloprid Calypso neonicotinoid broad-spectrum, systemic Rosy apple aphid. (Also likely to control capsids and sawfly, though not caterpillars or woolly aphid) safe

Choice of insecticides – Safety factors

  Hazards Harvest interval(days)  Max. no. sprays Buffer zoneWidth (m)
Anticholin-esterase?  Humans Fish & aquatic life Bees
acetamiprid no u h u 14 2 20
deltamethrin no h, i ed d 0 u 50
dodecylphenol ethoxylate no u u u 0 u u
fatty acids no u h u 0 u sm
flonicamid no u h u 21 3 sm
maltodextrin no i d d 0 20 sm
pyrethrins no h,i ed d 0 4 50
spirotetramat no h, i t u 21 2 sm
thiacloprid† no h, i h h 14 2 30
h=harmful, i=irritant, d=dangerous, ed=extremely dangerous, c=closed cab required for air assisted sprayers, sm=statutory minimum of 5 m for broadcast airassisted sprayers u=uncategorised/unclassified/unspecified

 

Control in organic orchards

Green apple aphid should be tolerated in established organic apple orchards because the pest only causes minor damage.

  • Emphasis should be placed on cultural control measures such as the provision of artificial refuges for earwigs and lacewings and of flowering herbs in and around the orchard to encourage predatory insects.
  • Where significant damage is being caused especially to young trees, as a last resort, localised, high volume sprays of fatty acids (Savona) should be applied when damaging infestations develop on young trees in summer if necessary.

 

 Further reading