A wide range of predators and parasites are natural enemies of rosy apple aphid. However, when weather and tree growth conditions are favourable in spring, population increase by the aphid is too rapid for natural enemies to prevent population increase and damage. Natural enemies have a greater effect when plant growth slows or ceases in summer.
Predation of aphids and their eggs in the autumn may be more significant as the number of overwintering eggs may be substantially reduced resulting in a smaller number of colonies developing in spring. This may be the reason why more colonies often develop in spring in insecticide treated than untreated orchards.
Predatory insects and spiders
- A wide range of predatory insects prey on rosy apple aphid including earwigs, predatory anthocorid and mirid bugs, lacewing and hoverfly larvae, predatory midge larvae, ladybird adults and larvae and spiders.
Parasitic wasps
- Ephedus persicae is the most important species in spring but contributes little to natural control of the aphid. Ant attendance and hyperparasitism decrease the impact of parasitic wasps.
Entomopathogens
- Outbreaks of fungal pathogens (Entomophthora sp) have been reported from rosy apple aphid colonies occasionally causing population crashes but their importance has not been investigated adequately.