Cabbage aphid
The cabbage aphid (mealy cabbage aphid in the UK) is a small grey-green aphid covered in a powdery white wax. It lives only on brassicas. It forms dense colonies on the undersides of leaves and in growing points, buds, heads and Brussels sprouts, and its feeding curls, wrinkles and yellows the leaves and stunts young plants. The bigger problem at harvest is usually contamination: aphids and honeydew in broccoli heads, cabbage and sprouts reduce their marketability. It also spreads cauliflower mosaic and other viruses. It does best in cool weather, so autumn crops are hit hardest. Hoverflies, lady beetles and a parasitoid wasp all attack it, but they may not keep up in a cool autumn.
A dense colony of Brevicoryne brassicae with bronze parasitised mummies on a kale leaf underside. Photo: pending.
Identification
Adults are grey-green but look grey or white, because they are coated in a dusty, waxy secretion that Kentucky compares to cigarette ash. Young nymphs may lack the wax and look green. Both adults and nymphs have dark heads and short cornicles (the paired "tailpipes" at the rear). Winged adults have a black thorax and dark legs. The RHS gives a length of up to 2.5 mm (about 1/10 inch). The colonies are dense and cluster on leaf undersides and growing points.
Its host range is the quickest check: only brassicas. The green peach aphid, which also feeds on brassicas, varies in colour but has no waxy covering (UC IPM). The RHS warns that mealy cabbage aphid can be mistaken for cabbage whitefly, but whiteflies rise in a cloud when the plant is disturbed and aphids do not. Bronze aphids in a colony are mummies left by the parasitoid wasp Diaeretiella rapae.
Easily confused with
- Cabbage whiteflyAlso a pestDisturb the leaf. Cabbage whiteflies fly up in a cloud; cabbage aphids stay put in dense grey, waxy colonies.
- Green peach aphidAlso a pestGreen peach aphid varies in colour but has no waxy covering. Cabbage aphid is grey-green under a grey, powdery coating, like cigarette ash.
- Aphid mummiesBeneficial — leave itParasitised cabbage aphids turn into bronze mummies. Leave them on the plant: the wasp developing inside is Diaeretiella rapae.
Damage symptoms
Cabbage aphids feed on the youngest leaves, flower buds and seed stalks at the top of the plant, and inside developing Brussels sprouts. Leaves wrinkle, curl downwards and yellow, and growth slows. On young plants the RHS says the growing point may be killed. Cabbage, cauliflower, broccoli and Brussels sprouts are the most severely affected. The most serious loss, though, is contamination: aphids and their sticky honeydew in heads and sprouts make them unsaleable, and UC IPM notes that dense waxy colonies are hard for sprays to penetrate. The aphid also transmits cauliflower mosaic and cabbage ring spot viruses, among others.
- Dense grey, waxy colonies under leaves and in growing points
- Leaves wrinkled, cupped or curled downwards, with yellow patches
- Stunted young plants, sometimes with the growing point killed
- Aphids packed into broccoli heads, cabbage and Brussels sprouts
- Sticky honeydew on the plant
- One heavily infested plant surrounded by clean ones
Lifecycle & degree days
In New England the cabbage aphid overwinters as eggs on brassica leaves, which hatch around April, or as nymphs in tunnels and greenhouses. Winged females blow into fields in spring, so early infestations are patchy. Through spring and summer only females are produced, and they give birth to live young without mating. Males and egg-laying females appear in autumn. In much of California, and in mild UK winters, it breeds all year. UMass puts its fastest reproduction at 50–68 °F (10–20 °C), and nymphs stop developing at 95 °F (35 °C). That is why numbers explode in late summer and autumn, especially on long-season crops such as Brussels sprouts.
- Overwinters
- Eggs on brassica leaves and stems; nymphs in tunnels; active all year in mild climates
- Reproduction
- Fastest at 50–68 °F (10–20 °C)
- Upper limit
- Nymphs stop developing at 95 °F (35 °C)
- Generations / yr
- Many; only females spring through summer
- First winged arrivals
- By about June 1 in Massachusetts
Host crops
The cabbage aphid feeds only on the cabbage family, including weeds such as charlock and shepherd's purse. Cabbage, cauliflower, broccoli and Brussels sprouts are the most severely affected. On kale the RHS says it can make the leaves inedible. Glossy brassica varieties, which lack the normal waxy bloom, tend to carry fewer cabbage aphids, according to UF/IFAS, but they attract more flea beetles.
Monitoring & action thresholds
UMass treats when more than 10% of plants have at least one aphid, or when more than 20% of 100 sampled leaves have aphids, and uses lower thresholds once the harvested parts start to form. UC IPM is stricter for cabbage (1–2% of plants infested) and Brussels sprouts (15%), but tolerates up to 100 aphids per broccoli or cauliflower plant before heading. For garden plants the RHS view is that aphids on established brassicas can be tolerated and left to predators, while young plants and kale need earlier action.
Check brassicas weekly, starting before the harvested parts begin to form, looking under leaves and into growing points and sprouts on both old and new growth. Wingless cabbage aphids do not move much, so one heavily infested plant among clean ones is typical. Removing that plant early can stop a colony spreading. Look for bronze mummies too: they show the parasitoid is already present.
Biological control
The parasitoid wasp Diaeretiella rapae lays its eggs inside cabbage aphids and leaves bronze mummies in the colonies. Lady beetles and hoverfly larvae are the main predators, and entomopathogenic fungi and heavy rain also knock populations back, which may explain why numbers swing so much from year to year. UMass says these natural enemies can suppress cabbage aphid but may not prevent the high densities of a cool autumn. It also finds predators better than parasitoids at controlling large populations. In high tunnels, UMass adds three purchasable options. Lady beetles work under row cover on winter greens. Predatory midges (Aphidoletes aphidimyza) enter diapause once days are shorter than 15 hours. Green lacewings are better bought as larvae than as eggs.
Cultural controls
Hygiene breaks the overwintering cycle, and early action beats spraying late.
- Dig in or remove brassica crops as soon as they finish; for autumn crops left standing, dig them in by early spring, before eggs hatch in April
- Control brassica weeds such as charlock and shepherd's purse in and around the garden
- Inspect transplants before planting
- Squash colonies by hand, or pull out a badly infested plant early in the season
- Try reflective mulches to deter aphids
- Use Bt rather than broad-spectrum sprays against caterpillars on the same crop, to spare the aphid's natural enemies
Chemical, last resort
- FlonicamidREI 12 h
- Insecticidal soapREI 12 h
- AzadirachtinREI 4 h
Sources
UC IPM Pest Management Guidelines: Cole Crops — Cabbage Aphid (Natwick et al., 12/20)
UC IPM, Relative Toxicities of Insecticides Used in Cole Crops to Natural Enemies
UMass Extension Vegetable Program, Cabbage Aphid (Higgins, updated Oct 2025)
Univ. of Kentucky ENTFACT-300, Cabbage Pests (Bessin, rev. 1/26)
RHS Advice, Mealy cabbage aphid
UF/IFAS EDIS EENY-119/IN276, Diamondback Moth (Capinera) — glossy varieties
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
Suggest a correction →Cabbage aphid by crop
The same pest behaves differently on different hosts. Each page below gives the host-specific control, rate and threshold.