Aphidius colemani
Aphid parasitoid wasp- Rate
- 0.25–4 /m² per release, at least three releases
- Temp
- 18–25 °C best; falls off above 30 °C
- Best for
- Preventive, from planting
Pest
Green peach aphid
Myzus persicae
The short answer
A small soft-bodied aphid, pale green to dark green or yellow, sometimes pink or red, that gathers on growing points and young leaves. Heavy colonies yellow and curl leaves and leave honeydew, but its main damage is the plant viruses it spreads — more than 100 of them.
hero macro · wingless adult on leaf underside
Wingless adult Myzus persicae with early-instar nymphs, tomato leaf underside. Photo: pending.
Identification
Wingless adults are about 1.7–2 mm, pear-shaped, pale green but also yellowish, pink, red or whitish in UC IPM's flower-crop guide, and dark green to yellow in its tomato and lettuce guides, so colour alone will not name it. The reliable tell under a 10× lens is the front of the head: the antennae rise from two bumps (tubercles) that lean towards each other, leaving a notch between them. Melon aphid, its commonest look-alike under glass, has a flat front to the head and short, entirely black cornicles.
Winged adults, 1.8–2.1 mm, have a black head and thorax and a dark patch on the abdomen. They land on almost any plant, deposit a few young and fly on — the habit that makes this species such an effective virus vector. It produces winged forms at lower densities than melon aphid, and its colonies sit mostly around growing points, where they are easier to spot.
Easily confused with
- Melon aphidAlso a pestMelon aphid has a flat front to the head, with no bumps at the antenna bases, and short, stout, all-black cornicles. Green peach aphid has converging bumps and long cornicles.
- Potato aphidAlso a pestPotato aphid is much bigger and more elongate than green peach aphid, with longer cornicles, and usually turns up on tomato tips later in the season.
- Aphid mummiesBeneficial — leave itA parasitised aphid swells into a crusty, golden-brown mummy, later with a round exit hole where the wasp left. Leave mummies on the plant: they mean parasitoids are working.
- Aphid midge larvaeBeneficial — leave itAphid midge larvae are bright orange, legless maggots up to about 1/8 in (3 mm) inside the colony. Aphids have legs and a pair of cornicles at the rear.
Damage symptoms
Light to moderate numbers do little to established plants. Heavy colonies on young growth cause water stress, wilting, yellowing and slower growth, and on pepper the leaves curl downward and inward from the edges. It makes less honeydew than some other aphids, but enough to foul fresh produce. The bigger cost is virus: UC IPM notes transmission takes only minutes and happens even when aphids are few, which is why infection is hard to prevent by killing aphids.
- Yellowing, wilting or stunting of young plants under heavy colonies
- Leaves curling down and inward from the edges, notably on pepper
- Sticky honeydew and black sooty mould on leaves and fruit below
- White cast skins on the leaves
- Mottling, mosaic or yellowing from viruses, even where few aphids are seen
- Ants tending the colonies
Lifecycle & degree days
Where winters are cold it alternates hosts: eggs overwinter on peach and other Prunus, several generations feed there in spring, then winged migrants move to vegetables and flowers; in autumn winged forms return to Prunus to mate and lay. In mild climates and under glass it can skip the egg stage and breed continuously, females bearing live young without mating. UC IPM says aphids commonly start giving birth at 7–10 days old depending on temperature (one study of this species found 6–17 days, averaging about 11), so a colony that looks trivial one week can be a problem the next.
- Lower threshold
- 3.3–4.3 °C (studies differ)
- Per generation
- 130–153 degree days °C, nymph to nymph (base 4 °C)
- Optimum
- About 24 °C (75 °F)
- Generations / yr
- Over 20 in mild climates
- Reproduction
- Live young without mating; eggs only in autumn on Prunus, in cold climates
J
F
M
A
M
J
J
A
S
O
N
D
Host crops
A very wide host range: hundreds of plants in more than 40 families (UF/IFAS); UC IPM counts over 200 hosts and UMass more than 400. In cold climates it overwinters as eggs on peach, apricot and plum, then moves to vegetables and flowers; broadleaf weeds such as bindweed, fat hen and pigweed carry it, and its viruses, between crops. Each crop hub below carries the seasonal calendar and starter beneficial program for that setting.
Monitoring & action thresholds
Action threshold
5–10 per card per week
UC IPM's figure for greenhouse ornamentals, on yellow sticky cards — but plants can be heavily infested before cards show it. For commercial lettuce UC uses 20 per plant before heading; for pepper and tomato it sets no number. There is no home-garden threshold: most plants tolerate light numbers, and on virus-sensitive crops infection happens even when aphids are very few.
Check plants at least twice a week while they are growing fast, turning leaves over and starting with the upwind edge and plants next to infested ones (UC IPM). Look for cast skins, honeydew and sooty mould as well as the aphids. Yellow sticky cards pick up winged adults, but wings appear mainly as colonies crowd, so inspect the plants too. Count mummies and predators: once crusty golden-brown mummies appear, UC expects aphid numbers to fall substantially within a week or two.
Beneficial
Biological control
Under glass, parasitoids work best released preventively: Koppert advises starting Aphidius colemani soon after planting, repeating at least three times, and expecting the first mummies 10–14 days after the first release. The wasp is less useful in the cold — UF/IFAS notes this aphid develops at lower temperatures than its parasitoids. Add the predatory midge Aphidoletes, which Koppert starts as soon as the first aphids are seen and repeats weekly until control; UC IPM describes it as well demonstrated in greenhouses. Outdoors, conserve rather than buy: hoverfly, ladybird and lacewing larvae arrive once aphids are plentiful, and bought ladybirds mostly fly off within days.
Aphidoletes aphidimyza
Aphid predatory midge- Rate
- 1–10 /m² per release, weekly
- Temp
- 20–26 °C best; needs warm nights and long days
- Best for
- From first aphids, weekly
Chrysoperla carnea
Green lacewing- Rate
- 2–20 /m² per release, weekly
- Temp
- 20–28 °C best; works above a 12 °C average
- Best for
- Infested patches
Syrphidae
Hoverflies- Kind
- Wild — attract it
- Best for
- Outdoors — attract, don't buy
Cultural controls
None of these clears an outbreak; they slow how fast one builds. High nitrogen feeds aphid reproduction, weeds and nearby Prunus supply the spring migrants, and ants guard colonies from their natural enemies.
- Use nitrogen sparingly, in slow-release forms
- Check transplants, and clear aphid-carrying weeds such as sowthistle before planting
- Lay silver reflective mulch to repel winged aphids from young plants
- Screen greenhouse vents with mesh of 0.355 mm or finer
- Keep ants off plants with sticky bands or bait stations
- Grow flowering plants nearby to feed predators and parasitoids
Chemical, last resort
Pyrethroids often fail on this aphid — resistance is widespread. UC IPM gives pyrethrins and soil-applied imidacloprid its strictest bee rating: never apply to, or let drift onto, flowering plants, weeds includedCheck any product before it goes on. Open the compatibility matrix →
- Insecticidal soapREI 12 h
- Neem oilREI 4 h
- PyrethrinsREI 12 h
- Imidacloprid (soil-applied, ornamentals only)REI 12 h
Rating: the effect on this pest's natural enemies if a spray hits them or they feed on treated plants. REI is the re-entry interval on farm and greenhouse labels; home labels usually give none, so follow the label.
Sources
UC IPM Pest Notes: Aphids, UC ANR Pub. 7404 (M.L. Flint; updated 07/2013)
UC IPM Floriculture & Nurseries Guidelines, Pub. 3392: Aphids (updated 01/2022)
UC IPM Guidelines: Green Peach Aphid on Peppers (11/2012), Tomato (12/2013), Lettuce (04/2017)
UC IPM, Relative Toxicities of Pesticides Used in Floriculture to Natural Enemies (updated 01/2022)
UC IPM Guidelines: Aphids on Strawberry (04/2024); Potato Aphid on Tomato (12/2013)
UC IPM Degree-Day Models: Green Peach Aphid (Whalon & Smilowitz 1979; Weed 1927; El Din 1976)
UF/IFAS EDIS EENY-222: Green Peach Aphid (J.L. Capinera; 2001, revised 2004)
RHS Advice: Aphids (accessed Sept 2026)
Koppert: Aphipar, Aphidend and Chrysopa product pages (accessed Sept 2026)
UMass Extension: Aphids on Greenhouse Crops (2022); Rincon-Vitova Aphidoletes bulletin
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
Suggest a correction →Green peach aphid by crop
The same pest behaves differently on different hosts. Each page below gives the host-specific control, rate and threshold.