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, under glass
Pest
Melon aphid
Aphis gossypii
The short answer
A small aphid, 1–2 mm long, that comes in almost any colour — mottled green, yellow, whitish or nearly black — but always has short, entirely black cornicles. It colonises the undersides of leaves on cucumbers, melons, squash, hibiscus and hundreds of other plants, curling them and coating what is below in honeydew. Unlike most aphids it is not slowed by hot weather, it is resistant to several insecticide classes, and it transmits cucumber mosaic and other cucurbit viruses within seconds of probing.
hero macro · mixed colour forms on a cucumber leaf underside
Wingless adults of Aphis gossypii, green and dark forms, cucumber leaf underside. Photo: pending.
Identification
Wingless adults are 1–2 mm and very variable: light green mottled with dark green is commonest, but whitish, yellow, pale green and dark green forms occur, and small yellow ones appear when plants are stressed or crowded. The legs are pale with black tips, and the cornicles are short, stout and entirely black. Winged adults, 1.1–1.7 mm, have a black head and thorax.
Green peach aphid, its commonest look-alike under glass, has two converging bumps at the front of the head and gathers at growing points; melon aphid's head is flat and its colonies spread through the plant, mostly on leaf undersides (UC IPM). It also produces winged forms only at higher densities than green peach aphid does (UC IPM). Spirea aphid is the other common confusion, and is told apart by the cauda under magnification (UF/IFAS).
Easily confused with
- Green peach aphidAlso a pestGreen peach aphid has bumps at the antenna bases that point towards each other, and long cornicles. Melon aphid has a flat head front and short, stout, all-black cornicles.
- Spirea aphidAlso a pestLook at the tail (cauda) under a lens. Melon aphid's is pale to dusky; spirea aphid's is dark brown to 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
Feeding on the leaf undersides yellows, curls and puckers the leaves, and the curled leaves then shelter the colony from sprays. Honeydew builds up on leaves and fruit and turns black with sooty mould. In cucurbits the bigger loss can be virus: UC IPM names cucumber mosaic, zucchini yellow mosaic and watermelon mosaic viruses, and UF/IFAS notes they are transmitted within 15 seconds, probably why insecticide and oil sprays fail to stop them.
- Leaves curled and puckered, colonies on the undersides
- Yellowing and stunting of young plants
- Sticky honeydew and black sooty mould on leaves and fruit
- White cast skins stuck to leaves
- Mosaic, mottling and distorted fruit from viruses
- Ants tending the colonies
Lifecycle & degree days
In the north, eggs overwinter on catalpa and rose of Sharon; winged females move to crops in spring, and sexual forms return in autumn. In the south, and at least as far north as Arkansas, it breeds without mating all year. It sometimes overwinters in greenhouses and arrives in gardens on transplants. A generation can take as little as a week, and heat does not slow it the way it slows most aphids.
- Nymph to adult
- About 7 days; generation in as little as a week
- Offspring / female
- About 70–80, at 4.3 a day (UF/IFAS)
- Optimum
- 21–27 °C (70–81 °F) for reproduction; 28.6 °C overall on cotton
- Lower threshold
- About 5.9–6.7 °C by instar (cotton, lab)
- Winter
- Eggs on catalpa and rose of Sharon in the north; breeds all year in the south
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Host crops
One of the widest host ranges of any aphid: USDA's AphID records it from over 135 plant families, and UF/IFAS counts at least 60 hosts in Florida and perhaps 700 worldwide. It is a serious pest of watermelon, cucumber and cantaloupe, less so of squash and pumpkin, and regularly injures citrus, cotton and hibiscus; UC IPM names it, with rose and potato aphids, among the aphids on roses, and its strawberry guidelines call it often the first aphid into strawberry fields each season and the hardest to control with insecticides. Rose of Sharon, a hibiscus, is one of its winter egg hosts.
Monitoring & action thresholds
Action threshold
5–10 winged per card per week
UC IPM's figure for greenhouse ornamentals, on yellow sticky cards. For cucurbits UC IPM says no threshold has been established, and for cotton it uses aphids per leaf. There is no home-garden number; on virus-sensitive cucurbits, killing aphids does not prevent infection, so reflective mulch and row covers matter more than counts.
Turn leaves over: this aphid lives on the undersides and spreads through the whole plant, so checking tips alone misses it. In cucurbits UC IPM advises setting yellow sticky cards before planting and checking the crop when aphids start appearing on them. Count mummies too — golden-brown ones from Aphidius or Lysiphlebus mean parasitoids are already working.
Beneficial
Biological control
Under glass, Aphidius colemani is the wasp sold for this aphid: in a North Carolina chrysanthemum trial it held melon aphid as low as imidacloprid did, with 49–83% parasitism, though it cost 4.7 times as much. Add the gall midge Aphidoletes on established colonies. Outdoors, the wild braconid wasp Lysiphlebus testaceipes can parasitise up to 99% (UF/IFAS), and lady beetles, lacewings and hoverfly larvae join in — but UC IPM warns that biological control does not reduce virus spread. Aphelinus abdominalis is a poor choice: in a lab host-range test it rarely even stung melon aphid (Monticelli et al. 2019).
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
- Established colonies
Chrysoperla carnea
Green lacewing- Rate
- 2–20 /m² per release, weekly
- Temp
- 20–28 °C best; works above a 12 °C average
- Best for
- Hot spots
Cotesia congregata and other Braconidae
Braconid wasps- Kind
- Wild — attract it
- Best for
- Outdoors — wild Lysiphlebus
Syrphidae
Hoverflies- Kind
- Wild — attract it
- Best for
- Outdoors — attract, don't buy
Hippodamia convergens and others
Ladybugs- Kind
- Wild — attract it
- Best for
- Outdoors, early spring — conserve, don't buy
Cultural controls
In cucurbits the aim is to keep winged aphids off young plants, since that is when virus does most damage. These come from UC IPM and UF/IFAS.
- Lay silver or white reflective mulch to repel winged aphids and cut virus incidence
- Use row covers to keep aphids off young cucurbits
- Check transplants, since the aphid can overwinter in greenhouses
- Avoid excess nitrogen
- Remove and destroy heavily infested plants and finished crops promptly
- Hose sturdy garden plants with a strong spray of water
Chemical, last resort
Widespread resistance to organophosphates and pyrethroids; sprays aimed at other pests often trigger melon aphid outbreaks. Soap and oil must hit the aphids and often miss colonies under lower leaves; pyrethrins and bifenthrin are highly toxic to bees, so never spray open flowersCheck any product before it goes on. Open the compatibility matrix →
- Insecticidal soapREI 12 h
- Narrow-range oilREI 4 h
- PyrethrinsREI 12 h
- BifenthrinREI 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-173: Melon Aphid or Cotton Aphid (J.L. Capinera; 2000, revised 2018–2024)
UC IPM Guidelines: Cucurbits, Melon Aphid, UC ANR Pub. 3445 (Natwick et al.; updated 05/2016)
UC IPM Floriculture & Nurseries Guidelines, Pub. 3392: Aphids (updated 01/2022)
UC IPM Guidelines: Cotton, Cotton Aphid (accessed Sept 2026)
UC IPM Pest Notes: Roses: Insects and Mites, UC ANR Pub. 7466 (updated 10/2019)
UC IPM, Relative Toxicities of Pesticides Used in Floriculture to Natural Enemies (updated 01/2022)
USDA AphID: Aphis gossypii (accessed Sept 2026)
Parajulee 2007, Environ. Entomol. 36: 666–672 (temperature and cotton aphid)
Vásquez, Orr & Baker 2006, J. Econ. Entomol. 99: 1104–1111 (A. colemani on chrysanthemum)
Koppert: Aphipar product page (accessed Sept 2026)
UC IPM Pest Notes: Aphids, UC ANR Pub. 7404
UC IPM Guidelines: Strawberry, Aphids (accessed Sept 2026)
Monticelli et al. 2019, Evol. Appl. 12: 1626–1640 (parasitoid host range)
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
Suggest a correction →Melon aphid by crop
The same pest behaves differently on different hosts. Each page below gives the host-specific control, rate and threshold.