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.
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.
- A full approval for spirotetramat (Batavia) on apples for the control of sucking insect pests will control green apple aphid, but growers may prefer to reserve its use for more difficult to control pests such as woolly aphid and rosy apple aphid. It must be applied after flowering and works best when pests are moving from brown wood to green tissue. It will prevent population build-up but does not offer pest ‘knockdown’.
- Use of synthetic pyrethroids, which are harmful to natural enemies, should be avoided.
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|
|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, Pyrethrum 5 EC||Extract from pyrethrum||broad spectrum||Aphids, apple blossom weevil, caterpillars, scale insects, spider mites||harmful|
|spirotetramat||Batavia||tetramic acid derivative||selective||Sucking insect pests||unclassified|
|thiacloprid||Calypso||neonicotinoid||broad-spectrum, systemic||Rosy apple aphid. (Also likely to control capsids, sawfly and weevils, 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|
|pyrethrins||no||h,i||ed||d||0 or 1 – Varies with product||Varies with product||50|
|spirotetramat||no||h, i||t||d||Start of ripening||2||sm|
|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 should be applied when damaging infestations develop on young trees in summer if necessary.