| Life Cycle: | Female rosy apple aphids lay oval shaped black eggs on the bark of apple trees in the fall. The eggs hatch in the spring at around the same time that tree buds begin to open. The emerging pink and purple nymphs will feed on the buds and leaves. There are five nymph instars, the last of which develops into a wingless female or 'stem mother' which subsequently gives birth to live young, usually when trees are in bloom. A second generation is produced at petal fall. Aphids can reproduce without mating (parthogenically). This method produces females. A third generation in late July will produce a greater percentage of winged offspring that will migrate to other hosts, particularly plantain. Several more generation will be produced until the fall when the winged females will mate with the few existing males and lay eggs on the bark of apple trees. |
| Host: | Apple trees are the primary host of rosy apple aphids. Narrowleaf plantain is a summer host. |
| Bio Region: | Throughout North America where apples are grown. |
| Damage: | The rosy apple aphid is a serious threat to apple producers. The adult and nymphs feed by sucking the juices from the leaves causing them to curl. They also cause growing shoots to twist and grow irregularly. Moulds can also develop on the leaf surface where the aphid leaves a reguritated substance referred to as honeydew. The mould shades the leaf surface and further weakens the plant. The saliva that the aphid transfers from leaf to fruit is toxic and causes deformed and undersized apples that are unmarketable. |
| Management: | Monitoring for aphids should begin in early June when tight clusters are forming. More than 20 aphids per cluster should be considered an infestation. Monitoring should begin within the inner canopy. |
| Controls: | Horticultural oils and insecticidal soaps are effective controls for aphids. Intervention is only recommended if more than 10% of fruit clusters are considered infested and there is insufficient predator populations. The use of horticultural oil is restricted in organic systems and the timing of its use is particularly important not only to its effectiveness but also because of potential phytotoxicity. Syrphids, lady beetles and lacewings are the primary predators of the rosy apple aphid. Syrphids in particular will kill 20 or more aphids per day. |
