Green apple aphid
Beginner
Scientific Name
Aphis pomi
Identification
Eggs:
- 1 mm long,
- Shiny,
- Black,
- Oval shaped,
- Rarely seen in orchards.
- 2 mm in length,
- Yellow-green to light green,
- Oval shaped with black cornicles (tail pipes),
- Five instars.
Adults:
- 2 mm in length,
- Oval shaped,
- Bright green with black cornicles and legs,
- Winged or wingless.
Damage
- Reduced vigour and growth of shoots,
- Reduced bud size and internodes’ length,
- Leaf curling,
- Honeydew produced by the aphids may drip onto fruit allowing sooty fungi to grow.
Often Confused With
- Rosy apple aphid- Immature green apple aphids have shorter antennae and less developed cornicles than immature rosy apple aphids, and are usually found in colonies on young terminals of apple trees. Rosy apple aphids are usually found on foliage, flower stalks and young fruit. Green apple aphids are also green in colour (not pink/purple).
- Mullein bug- Mullein bug nymphs lack the cornicles that green apple aphids have.
Period of Activity
Eggs hatch when buds burst and the first leaves are unfolding. There are many generations per year. They are most numerous during July and early August and usually remain on apples throughout the summer.
Scouting Notes
Monitor from bud break through harvest. Generally green apple aphids are of little concern after terminals harden off (late July or August). Check 100 terminals in a 4-6 ha block weekly throughout the summer. Pick 10 terminals per tree on 10 trees randomly, without visual bias towards infested terminals.
Be sure to scout for the presence of predators when assessing aphid populations in orchards. Resample orchards with high numbers of natural enemies present within a week to see if predators are providing control (see threshold).
Thresholds
The action threshold for green apple aphid is 400-600 aphids per terminal on 10% or more of terminals checked. If more than 20% of the aphid colonies have natural enemies, delay or eliminate an insecticide application. If sprays are delayed be sure to resample within a few days to monitor populations.
Advanced
The green apple aphid is widely distributed in Canada and the United States and first appears in apple orchards at bud break.
Scientific Name
Aphis pomi
Identification
Eggs are 1 mm long, shiny, black and oval shaped. Nymphs are 2 mm in length, yellow-green to light green, oval shaped with black cornicles (tail pipes) and have five instars. Adults are 2 mm in length, oval shaped and bright green with black cornicles (tail pipes) and legs. Adults can have wings or be wingless.
Green apple aphids are usually found close to major veins on the underside of the leaf. They suck sap from the leaf. Heavy infestations reduce vigour and growth of shoots. Feeding reduces bud size and internodes’ length, and causes leaf curling. Aphid damage can stimulate lateral branch growth and affect tree shape. Honeydew produced by the aphids may drip onto fruit allowing sooty fungi to grow. In heavy infestations, green apple aphids feed on immature apples and cause russetting.
Often Confused With
- Rosy apple aphid- Immature green apple aphids have shorter antennae and less developed cornicles than immature rosy apple aphids, and are usually found in colonies on young terminals of apple trees. Rosy apple aphids are usually found on foliage, flower stalks and young fruit. Green apple aphids are also green in colour (not pink/purple).
- Mullein bug- Mullein bug nymphs lack the cornicles that green apple aphids have.
Biology
Green apple aphids overwinter as eggs on suckers at the base of buds
on terminal shoots. Eggs hatch when buds burst and the first leaves
are unfolding. Newly hatched nymphs
are all females. Nymphs
begin to feed immediately on developing leaves, and are initially present
on terminal shoots, moving later to older cluster leaves. After feeding
for about two weeks and molting several times, nymphs
mature into wingless adults that reproduce without mating. These adults
give birth to live young, with populations building rapidly. Each female
can produce 50-100 live offspring. Young aphids develop in 7-10 days.
Green apple aphid populations build slowly on apples in early spring
(bloom, petal fall), and more
rapidly as average daily temperatures increase. Adult aphids in a colony
are generally wingless until crowded conditions induce the formation
of winged individuals that disperse to new hosts.
In late summer, males are produced as well as females. Females then mate with males and lay overwintering eggs. The greatest numbers of eggs are 15-20 cm from the tips of terminals. Eggs are seldom found on the large scaffold limbs or the trunks of apple trees.
Period of Activity
Green apple aphids overwinter as eggs on suckers at the base of buds on terminal shoots. Eggs hatch when buds burst and the first leaves are unfolding. Green apple aphid populations build slowly on apples in early spring (bloom, petal fall), and more rapidly as average daily temperatures increase. Green apple aphids are most numerous during July and early August. Depending on weather conditions, one generation is completed in two to three weeks. There are many generations per year. Green apple aphids usually remain on apples throughout the summer.
Scouting Notes
Begin monitoring at budbreak and continue until terminals harden off (late July or August). Check 100 terminals in a 4-6 ha block weekly throughout the summer. Pick 10 terminals per tree on 10 trees randomly, without visual bias towards infested terminals.
Be sure to scout for the presence of predators when assessing aphid populations in orchards. Resample orchards with high numbers of natural enemies present within a week to see if predators are providing control (see threshold below).
Thresholds
The action threshold for green apple aphid is 400-600 aphids per terminal on 10% or more of terminals checked. If more than 20% of the aphid colonies have natural enemies, delay or eliminate an insecticide application. If sprays are delayed be sure to resample within a few days to monitor populations.
Management Notes
- If the aphids do not have access to succulent new growth – and they feed on older leaves – the number of young produced drop by up to 50%. As a result green apple aphids are generally not a problem after terminals harden off (late July or August).
- If temperatures are 30-32°C and greater, females do not reproduce well. Aphids die when temperatures remain high for several days, and heavy rains wash aphid populations off leaves.
- A cool, wet spring favours aphid development and is unfavourable for the aphid’s natural enemies.
- Green apple aphids are one of the few apple pests often managed by biological control. A number of beneficial insects are effective for biological control in apple orchards.
- The most commonly observed predator of green apple aphid is Aphidoletes spp. (Cecidomyiidae), an orange maggot midge. Other natural enemies (predators) of apple aphids include hover fly larvae (Syrphidae), lacewing larvae (Chrysoperlidae and Hemerobiidae), lady beetle larvae/adults (Coccinellidae), mullein bug (Miridae), minute pirate bug (Anthocoridae), earwigs and some parasitic wasps (Braconidae). The natural enemy complex can be disrupted by insecticides applied against other pests. For more information on the toxicity of pesticides to beneficial insects click here.
- Manage nitrogen levels in plants to prevent excessive, lush terminal growth and help reduce aphid populations.
- Avoid summer pruning until terminal buds have set to prevent re-growth of shoots that are very attractive to aphids. Hand suckering in early June removes unnecessary vegetative growth that attracts green apple aphid.
- See OMAFRA Publication 360, Fruit Crop Protection Guide - Chapter 2 Apples or Apple Calendar only :
- Recommendations for green apple aphid at Special sprays, as well as in Non-bearing orchards
