Chemical control
A localised application of an approved insecticide should be considered where the pest is detected.
- If only rosy leaf curling, rosy apple or apple grass aphid are to be controlled, then flonicamid (Mainman) is likely to be a good choice as it is a selective aphicide.
- A full approval for spirotetramat (Batavia) on apples for the control of sucking insect pests will control rosy leaf curling aphid, but growers may prefer to reserve its use for more difficult to control pests such as woolly aphid. It must be applied after flowering and works best when pests are moving from brown to green tissue. It will prevent population build-up but does not offer pest ‘knockdown’.
- A recent EAMU for Flipper (fatty acids) has increased the available options should growers wish to reserve other insecticides for control of pests later in the season. It is known to complement the use of Batavia as it provides quick ‘knockdown’.
- The neonicotinoid acetamiprid (Gazelle) is also likely to be effective against rosy leaf curling aphid although its activity against other apple pests has not been explored sufficiently widely. It is known to control mussel scale very effectively when applied at the correct time for the pest at 90% crawler emergence.
- Earwigs are important natural enemies.
Note that these materials are largely ineffective against winter and tortrix moth caterpillars.
- The synthetic pyrethroid insecticide deltamethrin (Decis Forte etc) is also approved for control of aphids on apple but its use should be avoided as it is harmful to predatory mites and other insects.
It is important to apply insecticides in warm weather conditions at the full recommended dose and in a sufficient spray volume to give adequate cover.
It is also important to apply the insecticide early, before large colonies form which are difficult to control once surrounded by distorted mature leaves.
Cultural control
Rosy leaf curling aphid is a pest that occurs on the same trees year after year and only spreads slowly to adjacent trees.
- Where infestation is on a limited scale, it may be practical to remove and destroy infested shoots.
- Natural enemies should be encouraged by avoiding the use of broad-spectrum insecticides and by providing flowering plants in and around the orchard.
- Artificial refuges should be used to foster earwigs and other natural enemies such as lacewings.
- Ideally, a refuge should be provided in each tree. This may simply be some extra lengths of hollow tree tie round the stake.
- In orchards with high tree densities, it is likely to be impractical to provide more elaborate refuges such as half of a plastic drinks bottle containing a roll of corrugated cardboard.
Natural enemies
Predatory insects and spiders
- A wide range of predatory insects, including anthocorid, mirid and nabid bugs, ladybird adults and larvae, hoverfly, predatory midge and lacewing larvae and spiders feed on rosy leaf curling aphid.
Parasitic wasps
- The parasitic wasps Ephedrus persice, Ephedrus platigator and Trioxys angelicae are known to parasitise rosy leaf curling aphid.
- The parasites lay their eggs (usually singly) in the body of the aphid which continues to feed during the early stages of development of the parasite.
- The parasite eventually pupates within or beneath the skeleton of the aphid, forming a so-called ‘aphid mummy’.
- Although parasitic wasps are common natural enemies of rosy leaf curling aphid, they are not usually abundant enough to greatly reduce aphid populations.
Fungal parasites
- Outbreaks of fungal diseases (Entomophthora sp.) probably occur in rosy leaf curling aphid colonies. Outbreaks occur in warm, humid or wet conditions.
Biological control
Biological control approaches have not been developed for rosy leaf curling aphid.