Woolly aphid (Eriosoma lanigerum (Hausmann))
Woolly aphid colony with wax blown away
Woolly aphid is a sporadic pest of apple, which is sometimes present at low levels in orchards but only increases to cause problems in some years. Damage is expected to occur in years after warm winters when aphid colonies increase in early summer and spread onto extension growth. The entire life cycle is passed on the host tree.
Earwigs, ladybirds and the parasitic wasp Aphelinus mali are important natural enemies of woolly aphid and usually regulate populations to below damaging levels.
Artificial refuges should be provided for earwigs in orchards where woolly aphid is a problem and the use of pesticides harmful to earwigs and other natural enemies should be avoided.
The aphid itself is brown to greyish purple but is easily recognised as it produces conspicuous secretions of white woolly wax.
Orchards should be inspected for the pest (i.e. for the colonies that produce conspicuous masses of white woolly wax) at the end of blossom, in June and again in mid-summer.
The June assessment is critical. At least 25 trees per orchard should be inspected. If one or more trees in the sample has woolly aphid, in the extension growth, treatment with an insecticide is justified.
- Flonicamid (Mainman) is specifically recommended for control of woolly aphid on apple.
- Flonicamid (Mainman) is a good choice because it is selective, has low toxicity to natural enemies and is partially systemic.
- In recent years however, woolly aphid has become increasingly difficult to control with flonicamid and all other materials. Where all other products are failing to gain control, the best choice of product is spirotetramat (Batavia) which is approved on apples for controlling sucking insect pests and gains good control of woolly 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.
- Thiacloprid (Calypso) has little or no effect on woolly aphid. Calypso may possibly be harmful to earwigs, the most important natural enemy of woolly aphid. If this is the case, sprays of thiacloprid (Calypso) in mid- and late summer when earwigs are present in the tree, could cause later outbreaks of woolly aphid.
- Higher volume sprays are likely to give best results.
Insecticides approved for use on apple which are recommended to control woolly aphid or offer some incidental control when applied to control other pests
Thiacloprid (Calypso) is not listed here because although it is effective against other aphid species on apple and many other pests, it is ineffective against woolly aphid
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, 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, leafhoppers, scale insects||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, caterpiallars, spider mites||harmful|
|spirotetramat||Batavia||tetramic acid derivative||selective||Sucking insect pests||unclassified|
Choice of insecticides – Safety factors
|Hazards||Harvest interval(days)||Max. no. sprays||Buffer zoneWidth (m)|
|Anticholin-esterase?||Humans||Fish & aquatic life||Bees|
|spirotetramat||no||h, i||t||u||Start of ripening||2||sm|
|h=harmful, i=irritant, d=dangerous, ed=extremely dangerous, t=toxic, c=closed cab required for air assisted sprayers, sm=statutory minimum of 5 m for broadcast airassisted sprayers u=uncategorised/unclassified/unspecified* approval for use and storage of all products containing nicotine is allowed only until 08 June 2010|
Control in organic orchards
In organic orchards where the pest is often troublesome, emphasis should be placed on cultural control measures such as the provision of artificial refuges for earwigs and, if practicable, physical destruction of colonies in spring.
- High volume sprays of fatty acids (Savona) should be applied when damaging infestations develop.