Rosy Apple Aphid

Table of Contents

1. Introduction
2. Description
3. Biology
4. Damage
5. Monitoring and Management
6. Related Links

Introduction

The rosy apply aphid, Dysaphis plantaginea (Passerini), is found in most apple-growing regions of North America and is a pest on all apple cultivars. Cortland, Idared and Golden Delicious are the most susceptible to injury. This aphid feeds mainly on apply foliage, notably fruiting spurs, causing leaf chlorosis and curling. Their feeding indirectly stunts and deforms fruits in the cluster. This species is therefore considered the most economically significant of the aphid species that feed on apple in Ontario.

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Description

Overwintering eggs on bark and twig surfaces are 0.4 mm in length, shiny dark green to black in colour, and are oval-shaped (Figure 1). Young nymphs are pale yellow or pink. As they grow and feed, they become rosy brown or purple with a white or gray waxy covering (Figure 2).

Hatched nymphs are wingless females that are called stem mothers when they are mature. Adults are a dark purple-pink colour and are found in colonies on extension and terminal growth.

Figure 1. Overwintering eggs of rosy apple aphid on twig.

Figure 2. Colony of rosy apple aphids.

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Biology

Females deposit eggs on bark, especially at the base of the buds, in the fall. The eggs begin to hatch as tree buds open in the spring and continue to hatch over a two-week period. Aphid nymphs feed on the outside of leaf and fruit buds until leaves unfold.

Mature females usually produce live young shortly after or during bloom. The second generation matures and produces live young two or three weeks after petal fall. Unmated females can produce live young (parthogenesis) and only females are produced during the summer.

By mid-July a third generation will develop. Some of the aphids will remain on apple trees all summer while other develop wings and migrate to other hosts such as narrow-leaf and broadleaf plantain or dock. Several more generations develop on summer hosts until fall, when winged females return to the apple trees and produce live female young. These females develop on apple, mate with males, and deposit eggs that will overwinter to the following spring.

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Damage

Young aphids that hatch in spring damage the outside of the fruit and leaf buds by sucking sap from the tissues. During feeding, the aphids inject a toxin that deforms fruits and leaves (Figures 3 & 4). The aphids tightly curl and pucker the leaves that hide the aphid colony. Rosy apple aphids also produce honey-dew that may drip onto leaves and fruit. Sooty fungus colonizes the honeydew and fruit and discolours them. The presence of ants feeding on honeydew identifies aphid colonies.

Figure 3. Curling of terminals due to heavy rosy apple aphid feeding.

Figure 4. Deformed mature fruit due to rosy apple aphid injury.

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Monitoring and Management

Check for the presence of rosy apple aphids every week, beginning at tight cluster and continue until late June. Cortland, Idared and Golden Delicious are good cultivars to monitor for rosy apple aphids. For every 10-15 acres, examine five clusters from each of 20 trees for dwarf and semi dwarf plantings. For larger trees, examine 10 fruit clusters from each of 10 trees. A cluster is considered infested if more than 20 aphids are present. Check the interior portion of the tree, as rosy apple aphids usually appear there first.

Monitor for the presence of aphid predators in and around rosy apple aphid colonies. Predators may make chemical control unnecessary. Syrphids, lacewings and ladybird beetles are good aphid predators and often keep aphid populations below economically damaging levels. Pictures and descriptions of these predators can be found on the Beneficial Insects and Mites page.

Chemical control is only recommended if more that 10% of the fruit clusters are infested and few predators are identified. See the Pest Management Decision Guidelines in Chapter five of Publication 310: Integrated Pest Management for Ontario Apple Orchards for recommended materials.

If chemical control is justified, apply the insecticide in high volumes of water for good coverage. If possible, spray only susceptible cultivars where the threshold has been reached. it is important to detect rosy apple aphid infestations early, before mid-June are generally discouraged since the chemical has little chance of contacting aphid colonies once leaves are curled.

Dormant oil sprays applied for the control of European fruit scale or San Jose scale can suppress rosy apple aphids by killing overwintering eggs.

Related Links

• Beneficial Insects and Mites

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