Cowpea aphid (black legume aphid)

Aphis craccivora Aphis craccivora Koch, 1854 · formerly or also: Aphis leguminosae, Aphis medicaginis (misapplied)

groundnut aphid · English, Worldwide
pulgón negro de las leguminosas · Spanish, Spain and Latin America
豆蚜 (dòu yá) · Chinese, East Asia

The cowpea aphid is a small, shiny black aphid that forms dense colonies on the growing tips, flowers and pods of cowpea, groundnut, beans, lentil, faba bean, alfalfa and many other legumes. Heavy colonies stunt and distort plants and cover them with honeydew, but the aphid is even more important as a carrier of viruses, including groundnut rosette and cowpea aphid-borne mosaic virus. It thrives in warm, dry weather.

Colony of shiny black cowpea aphids (Aphis craccivora) with grey nymphs on a leaf. Photo: David Perez, CC BY 3.0, via Wikimedia Commons.

Type: Insect · Insect (aphid)
Classification: Animalia › Insecta › Hemiptera › Aphididae
Main crops: Cowpea, Groundnut, Common bean, Lentil, Faba bean, Alfalfa, Chickpea, Pigeon pea, Mung bean
Found in: Africa, Asia, Americas and Europe, Oceania
Chemical groups: IRAC 4A, IRAC 9B, IRAC 29 (mode-of-action groups, not products)
Last reviewed: 2026-10-20

Cowpea aphid scientific name, order and family

The scientific name of cowpea aphid is Aphis craccivora Aphis craccivora Koch, 1854, in the order Hemiptera, family Aphididae.

Older or alternative scientific names: Aphis leguminosae, Aphis medicaginis (misapplied).

Where it occurs

Found worldwide, especially in warm temperate, subtropical and tropical regions.

Region	Status
Africa	Widespread; key vector of groundnut rosette
Asia	Widespread
Americas and Europe	Widespread
Oceania	Widespread

Symptoms and identification of cowpea aphid

Cowpea aphids (Aphis craccivora) clustered on a plant stem. Photo: Luis Fernández García, CC BY-SA 4.0, via Wikimedia Commons.

The organism

Adult wingless females are about 1.5-2 mm long and shiny black, with black-and-white legs and black cornicles; nymphs are dull grey to black with a light waxy dusting. Winged adults have a black abdomen with dark patches. Colonies are almost entirely female and reproduce by live birth. Ants often tend colonies for their honeydew and protect them from predators.

Signs in the crop, stage by stage

Crop stage	What you see
Seedlings	Dense black colonies on growing points; stunted, twisted shoots; seedlings may wilt and die in dry weather.
Flowering and podding	Colonies on flower stalks and young pods; flower drop and malformed pods; honeydew, sooty mould and ants.
Virus symptoms	Mosaic, yellowing or rosetting in the crop, often spreading from aphid hotspots.

Life cycle of cowpea aphid

Life cycle of Cowpea aphid (black legume aphid) — diagram drawn by Laisha from the stages below. Durations depend on temperature.

In warm regions, females give birth to live young without mating all year round, and a nymph can become an adult in about a week. Winged forms develop when colonies are crowded or plants decline, and fly to new crops, spreading viruses. In cold regions the aphid may survive winter on perennial legumes. Because colonies can double in a few days in warm weather, early detection matters more than for most pests.

Stage	Duration	Notes
Nymph (4 instars)	About 5-8 days	Fast development in warm weather.
Wingless adult female	About 2-3 weeks	Gives birth to several young per day.
Winged adult	When crowded	Disperses and spreads viruses.

Temperature

Populations grow fastest in warm, dry weather (about 25-30 °C); heavy rain washes colonies off plants.

Generations

Many overlapping generations; continuous in warm regions.

Conditions that favour it

Warm, dry spells, drought-stressed crops, late planting, ant attendance, wild legume hosts and loss of natural enemies after broad-spectrum sprays.

Economic threshold level (ETL)

There is no single international threshold. Local action levels are based on the share of infested plants or colony size at seedling and flowering stages; where viruses such as groundnut rosette are important, management is preventive.

Thresholds are local. They depend on crop price, control cost, variety and natural-enemy activity, so use the figure your local extension service publishes where one exists.

Damage and yield loss from cowpea aphid

Direct feeding can kill seedlings and reduce flowering and pod set in dry seasons; virus transmission causes large losses, notably groundnut rosette in Africa, which can destroy entire groundnut crops in epidemic years. In seed crops of beans and cowpea, aphid-borne viruses can also be passed on through seed.

Monitoring

Check growing points and flowers of seedlings and young plants twice weekly in dry weather.
Look for ants on plants, a sign of aphid colonies, and for natural enemies such as ladybirds and parasitised (mummified) aphids.
Use yellow traps to detect winged aphid flights where virus risk is high.
After rain, recheck colonies; heavy rain often removes many aphids and may make treatment unnecessary.

How to control cowpea aphid (integrated management)

Control works best as a sequence: prevent, monitor, then act only when a threshold or a risk forecast says so, using the least disruptive option that works.

Cultural control

Plant early at recommended density; dense, uniform groundnut stands with early ground cover reduce aphid landing and rosette.
Remove volunteer legumes and virus-infected plants; avoid planting next to older infested crops.
Irrigate where possible during dry spells to reduce plant stress.
Avoid excessive nitrogen, which produces soft growth that favours aphid build-up.

Biological control

Ladybirds, hoverfly larvae, lacewings, parasitic wasps (such as Lysiphlebus and Aphidius species) and fungal diseases often control colonies when not disrupted by broad-spectrum sprays.

Host resistance

Aphid-resistant cowpea lines have been developed by breeding programmes in Africa, and some groundnut varieties resist rosette; resistance can vary with local aphid populations.

Chemical control of cowpea aphid — by mode-of-action group only

Laisha names chemical options only by their resistance-committee mode-of-action group (IRAC for insects, mites and nematodes, FRAC for fungi, oomycetes and bacteria, HRAC for weeds), never by active ingredient or product. What is registered differs by country and changes over time; the label and your local plant-protection authority decide what may be used, on which crop, at what rate and with what pre-harvest interval.

Seed treatments protect seedlings; foliar sprays are used when colonies are large, but they do not stop non-persistent virus transmission. What is registered differs by country and changes over time; follow the label and your local plant-protection authority.

Scheme	Group	Mode of action	Notes
IRAC	4A	Nicotinic acetylcholine receptor competitive modulators (neonicotinoids), seed treatment	Toxic to pollinators.
IRAC	9B	Chordotonal organ TRPV channel modulators	Feeding inhibitor.
IRAC	29	Chordotonal organ modulators, undefined target site	Selective.

Resistance management

Rotate groups, avoid unnecessary sprays and protect natural enemies.

Look-alikes and how to tell them apart

Cotton aphid — Dull green to dark aphids, not shiny black, and more common on cotton, cucurbits and okra.
Black bean aphid (Aphis fabae) — Dull, matt black aphids with white wax patches, mostly on faba bean and beet.
Green peach aphid — Pale green to pink aphids.

Host range

Mainly legumes, including cowpea, groundnut, beans, lentil, faba bean, pea, chickpea, alfalfa, clover and many wild legumes, and some plants of other families.

What is still uncertain

Biotypes may differ in host preference and virus transmission.
Thresholds are poorly defined for most crops.
The contribution of wild legumes to virus spread is poorly known in many regions.

Grow guides for its host crops

How to grow the crop well is the first line of defence. Laisha's free grow guides cover each crop from sowing to harvest:

How to grow Cowpea How to grow Groundnut How to grow Common bean How to grow Lentil How to grow Faba bean How to grow Alfalfa How to grow Chickpea How to grow Pigeon pea How to grow Mung bean

Not sure this is what you are seeing?Ask Laisha: describe the symptoms or send a photo, and get a reasoned first read with what to check next — for your crop, your stage and your region.Ask Laisha

Sources

Aphis craccivora (groundnut aphid) datasheet — CABI Compendium. https://doi.org/10.1079/cabicompendium.6192
Aphis craccivora (APHICR) — EPPO Global Database. https://gd.eppo.int/taxon/APHICR
Aphis craccivora settling behaviour and acquisition of cowpea aphid-borne mosaic virus in aphid-resistant cowpea — Entomologia Experimentalis et Applicata (Wiley). https://doi.org/10.1111/j.1570-7458.1985.tb00465.x
New sources of resistance in cowpea to the cowpea aphid (Aphis craccivora) — Journal of the Ghana Science Association. https://doi.org/10.4314/jgsa.v12i2.62811

Written by Laisha from the sources above, in its own words. This page is general reference, not a prescription: confirm identification locally and follow the label and your plant-protection authority.