Aphidius ervi
Aphid parasitoid wasp- Rate
- 0.25–2 /m² per release, weekly
- Temp
- 20–25 °C best; not effective above 30 °C
- Best for
- Preventive; weekly releases
Pest
Potato aphid
Macrosiphum euphorbiae
The short answer
The potato aphid is a large aphid, 2–4 mm long, in green and pink forms, found on tomato, potato, lettuce, roses and many other plants. Heavy colonies distort leaves and stems, stunt plants and leave honeydew and sooty mould, and it carries plant viruses. Outdoors, natural enemies are common and can provide control. Under glass, release the parasitoid Aphidius ervi, not A. colemani, which cannot develop in this aphid, and add Aphelinus abdominalis for hot weather.
hero macro · adult, wingless
Potato aphid (Macrosiphum euphorbiae), wingless adult. Photo: pending.
Identification
Wingless adults are 2–4 mm long and elongate, either green, often with a darker stripe down the back, or pink to red. They are often rather shiny, with red eyes, long legs, and long pale cornicles (the two tubes at the tail), sometimes darker at the tips.
The usual confusion is with green peach aphid, which is smaller. UC's reliable test needs a lens: the bumps between the bases of the antennae slope outward on potato aphid and converge on green peach aphid. On lettuce, potato aphid colonies usually start on the youngest leaves, while green peach aphid starts on the lower leaves and moves up.
Easily confused with
- Green peach aphidAlso a pestPotato aphid is much bigger and more elongate than green peach aphid, with longer cornicles and legs. Adults and young cluster tightly on the youngest leaves.
- Rose aphidAlso a pestLook at the cornicles. Potato aphid's are pale, at most with darker tips; rose aphid's are entirely black.
- 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.
Damage symptoms
On tomato, UC rates potato aphid more damaging than the other aphids. High populations distort leaves and stems, stunt plants and can cause necrotic spots on the leaves, and they produce copious honeydew on which sooty mould grows. On potato, the main damage is virus spread, although green peach aphid is a far more efficient vector of leafroll virus. On lettuce, aphids stunt seedlings and contaminate heads.
- Colonies of large green or pink aphids on shoot tips, stems and trusses
- Curled, distorted leaves and stems
- Necrotic spots on tomato leaves
- Honeydew and black sooty mould
- Stunted plants; virus symptoms in potato
Lifecycle & degree days
Potato aphid reproduces without mating, and the females give birth to live young, so colonies build quickly. In its native north-eastern USA it produces sexual forms and overwinters as eggs on rose. Elsewhere it usually overwinters as live-bearing females, and it is an especial problem in unheated greenhouses. It has been recorded on plants in at least 90 families.
- Adult length
- 2–4 mm (wingless)
- Host range
- At least 90 plant families
- Viruses carried
- Nearly 70 to about 100, by source
- Winter host
- Rose, in its native north-eastern USA
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Host crops
A highly polyphagous aphid: potato, lettuce, beets and many ornamentals, and plants in at least 90 families. It matters most on solanaceous crops, especially potato, and it also attacks many plants in the rose family. UC IPM lists it on strawberry, and it feeds on sweet pepper, which researchers use as a host plant for it.
Monitoring & action thresholds
Action threshold
50–60% of leaves infested (processing tomato)
UC's figure for processing tomatoes: sample the leaf below the highest open flower on 30 plants, and treat if 50–60% or more are infested. For potato in northern California the figure is 5% of leaves, and for lettuce, 20 aphids per plant before heading. UC gives no home-garden threshold. If mummies are increasing or predators appear to be gaining control, UC advises avoiding disruptive sprays.
On tomato, check the leaf below the highest open flower on a sample of plants, and count parasitised mummies and predators (lady beetles, lacewing larvae, hoverfly larvae) as well as aphids. On lettuce, check the field edges twice a week. Under glass, check shoot tips and trusses, and release parasitoids weekly through the period potato aphid is expected.
Beneficial
Biological control
Match the parasitoid to the aphid. Aphidius colemani, sold for small aphids, stings potato aphid but cannot develop in it; the larger Aphidius ervi is sold for this species. Aphelinus abdominalis is the heat-tolerant partner, working up to 35 °C, and Biobest advises combining A. ervi with the gall midge Aphidoletes, which it calls a complement to parasitoids. Outdoors, UC finds parasites and predators common enough to provide control.
Aphelinus abdominalis
Aphid parasitoid wasp- Rate
- 0.25–4 /m² per release, repeated
- Temp
- 15–35 °C (59–95 °F); outperforms Aphidius above 28 °C
- Best for
- Hot weather; release near colonies
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
- Alongside A. ervi, on colonies
Cultural controls
Outdoors, the most useful thing is not to disrupt the natural enemies that usually bring potato aphid down.
- Avoid broad-spectrum sprays while mummies and predators are increasing
- Control weeds in and around the crop
- Do not rely on Mi-gene tomato varieties against the pink form
- Where you do spray, get thorough coverage through the canopy
Chemical, last resort
Soap gives under 50% control; broad-spectrum sprays kill the parasitoids. Dimethoate is highly toxic to bees (UC class I) and is a commercial productCheck any product before it goes on. Open the compatibility matrix →
- Insecticidal soapREI 12 h
- FlonicamidREI 12 h
- PymetrozineREI 12 h
- SpirotetramatREI 24 h
- Dimethoate (commercial only)REI 48 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 Tomato Pest Management Guidelines — Potato aphid (Natwick et al., 2013)
UC IPM, Relative Toxicities of Insecticides Used in Tomatoes to Natural Enemies (2016)
UC IPM Potato Pest Management Guidelines — Aphids (updated 2019)
UC IPM Lettuce Guidelines — Green peach and potato aphids (updated 2017)
InfluentialPoints — Macrosiphum euphorbiae, potato aphid
AphidNet — Macrosiphum euphorbiae fact sheet
Prado et al., Insects 6:538 (2015) — Aphidius host range
Koppert — Aphidius ervi and Aphelinus abdominalis species pages
UC IPM Strawberry Pest Management Guidelines — Aphids (updated 2024)
UConn IPM — Biological control of aphids (Aphidius ervi, A. colemani, Aphelinus)
Biobest — Ervi-System and Aphidoletes-System product pages
Mölck & Wyss, Commun Agric Appl Biol Sci 68:167 (2003) — potato aphid on sweet pepper
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
Suggest a correction →Potato aphid by crop
The same pest behaves differently on different hosts. Each page below gives the host-specific control, rate and threshold.