Syrphidae
Hoverflies- Kind
- Wild — attract it
- Best for
- Attract with a mix of flowers
Pest
Oleander aphid
Aphis nerii
The short answer
A bright yellow aphid, 1.5–2.6 mm long, with black legs, antennae, cornicles and tail. It lives on milkweeds and oleander, where colonies build fast into dense yellow sleeves on stems, tips and pods. The damage is mostly honeydew and sooty mould. On milkweed grown for monarchs the real risk is the treatment: systemic insecticides used on milkweed have killed monarch caterpillars for up to four weeks after treatment. Squash, prune or hose the aphids instead, and let the predators come.
hero macro · yellow colony on a milkweed stem
Wingless adults and nymphs of Aphis nerii on Asclepias stem. Photo: pending.
Identification
Wingless adults are 1.5–2.6 mm, bright yellow with black cornicles, antennae, legs and cauda — the combination makes it the easiest aphid in the garden to name. Winged adults are yellow and black with dark wing veins. Nymphs look like small wingless adults. All adults are female: UF/IFAS says it is thought to reproduce without males, and a 2011 genetic study found each southern US population it sampled was a single clone.
Two other aphids specialise on common milkweed: Aphis asclepiadis and Myzocallis asclepiadis. In experiments by Cornell researchers the oleander aphid outcompeted both. The bright colour is a warning: the aphid stores the milkweed's heart poisons, which deters some birds and spiders, but UF/IFAS notes they do not appear to harm its insect predators and parasitoids.
Easily confused with
- Aphid midge larvaeBeneficial — leave itAphid midge larvae are orange and sit among the aphids, but they are legless maggots up to about 1/8 in (3 mm). Oleander aphids are yellow, with black legs, antennae and cornicles.
- Aphid mummiesBeneficial — leave itA parasitised aphid becomes a papery, light-brown, swollen mummy, later with an exit hole. Leave it on the plant: a wasp is developing inside.
- Hoverfly larvaeBeneficial — leave itHoverfly larvae are legless and maggot-like, tapering towards the head, and most are 1/5–4/5 in (5–20 mm) long when grown. Aphids have legs and a pair of cornicles.
Damage symptoms
UF/IFAS describes the damage as mainly aesthetic: large, unsightly colonies, sticky honeydew and the black sooty mould that grows on it, sometimes deformed shoot tips. Repeated heavy infestations can stunt plants in nurseries. For a monarch garden the indirect cost matters more: in University of Florida trials, monarchs laid three times more eggs on aphid-free tropical milkweed, and caterpillars on it ate and weighed about twice as much.
- Stems, tips and seed pods sleeved in bright yellow aphids
- Sticky honeydew and black sooty mould on leaves below
- Deformed shoot tips under heavy colonies
- Yellow-and-black winged adults once colonies crowd
- Papery tan mummies — parasitised aphids
- Fewer monarch eggs on heavily infested plants
Lifecycle & degree days
There is no egg and no male. Females give birth to live nymphs that are clones of themselves, the nymphs moult five times, and colonies build quickly on the tender growth. Winged adults appear when a colony is crowded or its plant is failing, and fly to new milkweeds. In a 2011 study of three southern US populations, which die out and are recolonised, each population sampled was a single clone.
- Reproduction
- Thought to be females only; live young, no eggs (UF/IFAS)
- Nymph stages
- Five instars; no pupa
- Winged forms
- When colonies crowd or the plant declines
- Southern US
- Each sampled population one clone — 'superclones' (2011)
- Origin
- Probably Mediterranean, with oleander
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Host crops
Mostly oleander and milkweeds, including butterfly weed (Asclepias tuberosa) and scarlet or tropical milkweed (A. curassavica); UF/IFAS also lists wax plant and vinca, occasional finds on other families, and records on citrus, and USDA's AphID records 16 other plant families. UF/IFAS does not recommend tropical milkweed in Florida, where it has been assessed as invasive.
Monitoring & action thresholds
Action threshold
None — tolerate, then remove by hand
UF/IFAS gives no garden threshold. It says other insecticides are not necessary in the home garden, given the level of natural control and the ease of killing aphids with soap and oil, and that they are incompatible with butterfly host plants — though in Florida nursery trials soap did not hold aphids below the growers' threshold. If you use oil, keep it off open milkweed flowers: UC IPM puts it in bee class II (spray only between sunset and midnight, if the label allows). Act when colonies are spreading and no mummies or predator larvae are in them — by pruning, squashing or hosing, not spraying.
Check milkweed weekly, turning pods and tips over, and look at the colony, not just the aphids. Papery tan mummies, hoverfly larvae, lacewing larvae, ladybird larvae and the tiny orange larvae of the aphid midge in a colony all mean it is already being eaten. Before any removal, check the same stems for monarch eggs and small caterpillars first.
Beneficial
Biological control
Natural control of this aphid can be very effective (UF/IFAS). The wasp Lysiphlebus testaceipes parasitises it, and hoverfly, lacewing, ladybird and aphid midge larvae all feed in the colonies; in a field study on milkweed, aphid populations fell faster where midges, lacewings and syrphids were more numerous. University of Florida researchers cite work showing that more kinds of flowers in a milkweed garden raised predator numbers. Bought-in parasitoids may not help: in lab tests the commercial wasps Aphelinus abdominalis and Aphidius ervi stung this aphid but could not develop in it.
Cotesia congregata and other Braconidae
Braconid wasps- Kind
- Wild — attract it
- Best for
- Wild Lysiphlebus — leave the mummies
Hippodamia convergens and others
Ladybugs- Kind
- Wild — attract it
- Best for
- Larvae feed in colonies — conserve
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
- Arrives on its own outdoors
Chrysoperla carnea
Green lacewing- Rate
- 2–20 /m² per release, weekly
- Temp
- 20–28 °C best; works above a 12 °C average
- Best for
- Larvae feed in colonies — conserve
Cultural controls
UF/IFAS recommends pruning and hosing on milkweed grown for butterflies, and less water, pruning and fertiliser on oleander. Check each stem for monarch eggs and caterpillars first.
- Prune out heavily infested shoots and pods and throw them away
- Dislodge colonies with a strong stream of water from the hose
- Squash colonies between finger and thumb
- Water, prune and fertilise less on oleander, since it all drives the tender shoots the aphid prefers
- Plant a mix of flowers near the milkweed to build predator numbers
- Buy milkweed from nurseries that can say it was grown without systemic insecticides
Chemical, last resort
Nothing but soap or oil on milkweed: UF/IFAS calls other insecticides incompatible with butterfly host plants, and in Florida trials systemics killed monarch caterpillars up to 4 weeks after treatmentCheck any product before it goes on. Open the compatibility matrix →
- Insecticidal soapREI 12 h
- Narrow-range oilREI 4 h
- PyrethrinsREI 12 h
- Imidacloprid (soil-applied)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
UF/IFAS EDIS EENY-247: Oleander Aphid (H.J. McAuslane; 2001, revised 2017)
UF/IFAS Gardening Solutions: Milkweed (accessed Sept 2026)
Mach et al. 2024, Environ. Entomol. 53: 648–658 (insecticides, monarchs and oleander aphid)
Mach et al. 2023, PLoS ONE 18: e0288407 (aphid-infested milkweed and monarchs)
Harrison & Mondor 2011, PLoS ONE 6: e17524 (oleander aphid superclones)
Smith, Mooney & Agrawal 2008, Ecology 89: 2187–2196 (three milkweed aphids)
Meier & Hunter 2021, J. Anim. Ecol. 90: 1341–1352 (aphid midges on milkweed)
Monticelli et al. 2019, Evol. Appl. 12: 1626–1640 (parasitoid host range)
USDA AphID: Aphis nerii (accessed Sept 2026)
UC IPM Floriculture & Nurseries Guidelines, Pub. 3392: Aphids treatment table (updated 01/2022)
UC IPM, Relative Toxicities of Pesticides Used in Floriculture to Natural Enemies (updated 01/2022)
Rincon-Vitova, Aphidoletes product bulletin (accessed Sept 2026)
UC IPM Natural Enemies Gallery: Syrphids (accessed Sept 2026)
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
Suggest a correction →Oleander aphid by crop
The same pest behaves differently on different hosts. Each page below gives the host-specific control, rate and threshold.