Soybean aphid

Aphis glycines Aphis glycines Matsumura, 1917

大豆蚜 (dàdòu yá) · Chinese, East Asia
ダイズアブラムシ (daizu aburamushi) · Japanese, Japan
soyabean aphid · English, United Kingdom and Commonwealth

The soybean aphid is a small yellow aphid from East Asia that colonises the undersides of soybean leaves and stems. Large colonies reduce pod numbers and seed size and cover plants with honeydew and sooty mould. After it was found in North America in 2000, it spread across the Midwest within a few years and became the main insect pest of soybean there, leading to one of the best-studied economic thresholds of any field-crop pest.

Colony of pale yellow-green soybean aphids (Aphis glycines) on a soybean leaflet. Photo: Christina DiFonzo, Michigan State University, CC BY 3.0 US, via Wikimedia Commons.

Type: Insect · Insect (aphid)
Classification: Animalia › Insecta › Hemiptera › Aphididae
Main crops: Soybean
Found in: East Asia, South-East Asia, North America
Chemical groups: IRAC 4C, IRAC 4D, IRAC 3A (mode-of-action groups, not products)
Last reviewed: 2026-10-20

Soybean aphid scientific name, order and family

The scientific name of soybean aphid is Aphis glycines Aphis glycines Matsumura, 1917, in the order Hemiptera, family Aphididae.

Where it occurs

Native to China, Japan, Korea and other parts of East and South-East Asia; found in North America since 2000 (first in Wisconsin) and now across the soybean-growing areas of the United States and Canada.

Region	Status
East Asia	Native; widespread
South-East Asia	Present
North America	Widespread since 2000

Symptoms and identification of soybean aphid

Winged soybean aphid on a soybean leaf. Photo: NY State IPM Program at Cornell University from New York, USA, CC BY 2.0, via Wikimedia Commons.

The organism

Wingless adults are small (about 1.5 mm), pale yellow to lime-green, with black tips on the cornicles and a pale tail. Winged adults have a dark head and thorax. Colonies are found on the undersides of upper leaves and on stems and pods.

Signs in the crop, stage by stage

Crop stage	What you see
Early colonisation	Small colonies on new leaves at the top of the plant, often tended by ants.
Heavy infestation	Dense colonies on leaves, stems and pods; sticky honeydew and black sooty mould; leaves puckered or yellowing.
Yield effects	Stunted plants, fewer pods and smaller seeds, especially when large populations occur during flowering and early pod set.

Life cycle of soybean aphid

Life cycle of Soybean aphid — diagram drawn by Laisha from the stages below. Durations depend on temperature.

In North America, eggs on buckthorn hatch in spring; after two or three generations, winged aphids fly to soybean. On soybean, females give birth to live young without mating, and colonies can double in a few days in mild weather. Winged forms spread between fields during summer. In autumn, sexual forms return to buckthorn and lay overwintering eggs.

Stage	Duration	Notes
Egg on buckthorn	Winter	Overwintering stage.
Spring generations on buckthorn	Spring	Produce winged migrants.
Summer generations on soybean	About 1 week each	Rapid population growth.
Autumn return to buckthorn	Autumn	Mating and egg laying.

Temperature

Populations grow fastest at about 22-25 °C and slow above about 30 °C.

Generations

About 15 or more generations per year, most of them on soybean.

Conditions that favour it

Mild summer temperatures, buckthorn near soybean fields, few natural enemies early in the season, and potassium-deficient soybean.

Economic threshold level (ETL)

Multi-state research in the north-central United States calculated an average economic threshold of about 273 aphids per plant (range 111-567), giving about seven days of lead time before the economic injury level of about 674 aphids per plant; extension services round this to 250 aphids per plant with populations increasing, through growth stage R5. Values for other regions may differ.

Crop	Threshold	Unit	Crop stage	Region	Source
Soybean	About 250 aphids per plant on average (calculated mean 273), with populations increasing	aphids per plant	Flowering to beginning seed (through R5)	North-central United States	Ragsdale et al. 2007, Economic threshold for soybean aphid, Journal of Economic Entomology

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 soybean aphid

Uncontrolled outbreaks have reduced yields by up to about 40% in North America; the aphid also transmits viruses such as soybean mosaic virus and alfalfa mosaic virus.

Monitoring

From early vegetative stages, count aphids on whole plants in several parts of the field weekly, using speed-scouting methods where available.
Note whether populations are increasing over consecutive visits and whether natural enemies are abundant.
Scout more often during flowering and early pod set, when the threshold applies.

How to control soybean 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

Maintain good potassium fertility, since deficient plants support larger aphid populations.
Removing buckthorn near fields is sometimes suggested, but its effect on field populations is uncertain.

Biological control

Lady beetles (especially the multicoloured Asian lady beetle), minute pirate bugs, lacewings, hoverflies, parasitic wasps (such as Aphelinus certus) and fungal diseases often keep populations below the threshold; avoid unnecessary sprays to conserve them.

Host resistance

Varieties with Rag resistance genes reduce aphid growth; virulent biotypes that overcome some genes are known, so stacked genes are more durable.

Chemical control of soybean 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.

Spray only when the threshold is reached. Resistance to pyrethroids has been documented in parts of the north-central United States. 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	4C	Nicotinic acetylcholine receptor competitive modulators (sulfoximines)	Rotate.
IRAC	4D	Nicotinic acetylcholine receptor competitive modulators (butenolides)	Rotate.
IRAC	3A	Sodium channel modulators (pyrethroids)	Resistance reported; harmful to natural enemies.

Resistance management

Use thresholds to avoid unnecessary sprays, rotate groups, and check results a few days after spraying for signs of resistance.

Look-alikes and how to tell them apart

Cotton aphid — Variable green to dark aphids on cotton, cucurbits and okra; rarely colonises soybean heavily.
Potato leafhopper and other leafhoppers — Wedge-shaped, jumping insects that cause leaf edge yellowing, not colonies.
Spider mites — Fine stippling and webbing in hot, dry weather, with tiny mites instead of aphids.

Host range

Soybean is the summer host. In North America the aphid spends the winter as eggs on buckthorn (Rhamnus species); in Asia buckthorn species also serve as winter hosts.

What is still uncertain

Thresholds have not been validated in all regions where soybean is grown.
The role of buckthorn removal and of long-distance migration in field outbreaks is uncertain.

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 Soybean

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 glycines (soyabean aphid) datasheet — CABI Compendium. https://doi.org/10.1079/cabicompendium.6203
Aphis glycines (APHIGY) — EPPO Global Database. https://gd.eppo.int/taxon/APHIGY
Economic threshold for soybean aphid (Hemiptera: Aphididae) — Journal of Economic Entomology (Oxford University Press). https://doi.org/10.1093/jee/100.4.1258
Ecology and management of the soybean aphid in North America — Annual Review of Entomology. https://doi.org/10.1146/annurev-ento-120709-144755

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.