Fruit IPM Fact Sheet

Apple Grain Aphid

Scientific Name – Rhopalosiphum fitchii (Sanderson)

Family – Aphidae

This aphid is conspicuous in early spring on the swollen buds of apples.

Life Stages
Egg: The egg is similar to that of the rosy apple aphid.

Nymph: Newly emerged nymphs are dark green. The second and third instars are yellowish green. The fourth instar closely resembles the adult. The very short antennae and cornicles of the nymphs readily distinguish the apple grain aphid from the rosy apple and apple aphids.

Adult: Adults are yellowish green with a dark green line running down the middle of the back and four or five cross-lines of the same color. The males are a light greenish brown and more slender then the females.

Host Range
This aphid attacks apple, pear, hawthorne, plum, quince, grasses and grains. It is present in most apple-growing regions in Canada and the United States.

Injury or Damage
No control for this aphid is required because it does not attack fruit, and the feeding on the foliage causes little, if any, distortion. The first of the winged forms leaves the apple at petal fall and migration continues for about two weeks. At the end of that time, apple grain aphids are not found on the trees. They may injure young wheat in the fall.

Factors Affecting Abundance
Cold, wet weather in the spring favors the aphids because it creates unfavorable conditions for aphid parasites and predators. Cold rains occurring when eggs are about to hatch can abort hatching.

Life History
The eggs are laid in the autumn on apples, and the aphid spends the winter in the egg stage. The eggs begin hatching in the spring a week to 10 days earlier than those of the apple aphid or the rosy apple aphid. Hatching continues over a considerable period – usually about 10 days if the weather is favorable. The stem mothers become mature in early to mid-May and eggs hatch when the buds are swelling. The aphids may be found congregated at the very tips seeking entrance even before the tips show green. As the buds unfold, the aphids feed on the tender foliage but do not cause marked curling of the leaves.

The stem mothers reach maturity about two weeks after hatching from the eggs. When abundant, as it frequently is, this aphid may almost completely cover the buds. As soon as the buds open, the young aphids swarm over the leaves. They feed almost exclusively on the opening foliage but do not cause any curling. They never attack the tender twigs and have never been observed feeding on the water sprouts as the apple aphid commonly does.

The stem mothers mature in early to mid-May. Deposition of young usually begins within 24 hours after the last molt. Young may be produced for about 30 days, and the total production of young averages about 75 per female. The young nymphs of a second generation feed almost exclusively on the foliage. Very seldom have they been found on the developing fruit.

The majority of this generation acquires wings and migrates to the summer host plants. A small proportion are wingless viviparous females that continue to produce young on the apple. Normally, a few third-generation individuals occur. All of these are winged and migrate to their summer host plants – grains and grasses. All offspring produced in these first three generations are parthenogenetic females. Most of them leave the apples around the petal-fall stage, though a few may stay on until July.

In the fall, winged viviparous females return to the apple tree and give birth to wingless oviparous females. The male aphids develop on grains or grasses and later fly to apples, where they find and fertilize the females before egg laying starts. After mating, the female starts depositing eggs. The shiny black eggs are laid on the bark all over the tree, but mostly on the twigs near the buds.

Monitoring
Because this is the earliest aphid found in the orchard, it is important to recognize this species. Do not treat for aphids if this is the only aphid found in damaging numbers. The apple grain aphid is not an economic pest, and it will leave the orchard shortly after petal fall.

Control
No control measures are required. However, it is important to recognize the apple grain aphid to avoid applying sprays when large colonies of this species only are present early in the season. The simplest method for field recognition is to examine adults for a dark green line running down the middle of the back with four or five dark green cross-lines.

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Created: June 20, 1999