Field Identification
A dark, soft-bodied aphid complex that colonizes legumes, beets, spinach, and many broadleaf crops and weeds. Colonies extract phloem sap, curl leaves, stunt seedlings, and coat foliage with sticky honeydew that grows sooty mold. It vectors several plant viruses where those diseases occur. Populations surge in cool, lush growth and can appear anywhere legumes and alternate hosts overlap from temperate through subtropical parts of the Americas (zones 3–13), often riding wind currents between seasons.
Adults are shiny black to dark olive, about 1/16–1/8 inch (1.5–3 mm) long, with paired tailpipe-like cornicles. Winged forms have a darker thorax and disperse to new hosts. Nymphs resemble miniature adults and cluster on growing tips and undersides. Ants tending colonies are a visible clue to heavy honeydew production.
How to Deal With It
Organic Control Methods
Insecticidal soap or horticultural oil knocks down exposed colonies with complete coverage, especially leaf undersides; repeat every few days while migrations continue. Neem-based products can reduce feeding and reproduction. Avoid spraying open flowers visited by pollinators; apply in early morning or evening and spot-treat hotspots when possible.
Lady beetles (Coccinellidae), syrphid fly larvae (Syrphidae), lacewings (Chrysopidae), and parasitic wasps such as Aphidius spp. and Aphelinus spp. attack bean aphid. Preserve flowering strips and avoid tank-mixing soaps or oils on the same day as releasing purchased beneficials.
Avoid over-fertilizing with soluble nitrogen that produces soft, aphid-magnet growth. Intercrop with less favored species to slow colony spread; remove nearby weed reservoirs (lamb’s-quarters, dock, mustards) that host early flights. Harvest or clip heavily infested tips on leafy greens to set back colonies before seed staging.
A strong water rinse dislodges colonies from sturdy plants; repeat every 2–3 days on beans and beet greens. Sticky traps monitor winged arrivals in high tunnels and greenhouse starts without replacing biocontrol.
Scout undersides of terminal leaves twice weekly during cool, humid weather. Use reflective mulches early in season where labels allow to confuse incoming alates. Rotate legume blocks in market gardens so successive lush stands do not line up with peak migrations.
Let Nature Handle It
Natural Enemies
- Aphidius spp. (Braconidae)
- Lady Beetles (Coccinellidae)
- Syrphid Fly Larvae (Syrphidae)
- Lacewing larvae (Chrysopidae)
Threat Map