Plant Problem Diagnosis Key / Pests
Pest
Aphids
Aphididae
Soft, pear-shaped insects that cluster on new growth and leaf undersides and suck sap. They reproduce without mating, so numbers can explode in days, and some species spread viruses.
Signs
- Clusters of green, black, gray, yellow or pink insects with two tubes (cornicles) at the rear.
- Curled, puckered new leaves; sticky honeydew and white shed skins below.
- Ants running up and down the stems, tending the colony.
What favors it
Soft, fast new growth, heavy nitrogen, ants that guard them, and sprays that kill their natural enemies.
Prevention
- Feed nitrogen to need, not to excess.
- Plant flowers (alyssum, dill, yarrow) that feed hoverflies and parasitic wasps.
- Check new growth and leaf undersides weekly.
Often confused with
Sources
- Aphids in home yards and gardensUniversity of Minnesota Extension
- AphidsMontana State University Extension
- Aphids in Home GardensUniversity of Maryland Extension
Treatment by crop
Cultural, biological and chemical options in the order to use them, and notes written for each crop.
Identification is free. Treatment is on the Home and Pro plans.
Questions in the key that lead here
- Look the plant over, leaf undersides included. Are insects, mites, slugs, eggs, webbing or droppings on it?
Yes, something living or its traces - What is on the plant?
Small insects, clustered or flying - Do they fly up when the plant or the soil is disturbed?
No, they stay put or crawl - What kind of insect?
Soft, pear-shaped, slow
Not a match? Start the key or describe what you see.
More photos
More from university Extension: search Extension pages on aphids, or find a plant diagnostic lab through your state's Extension.
Other pests
- Bagworms
- Bark beetles of pine and spruce
- Broad mites and cyclamen mites
- Caterpillars
- Cicada and twig-cutting damage
- Colorado potato beetle
- Cucumber beetles
- Cutworms
- Elm leaf beetle
- Emerald ash borer
- Flea beetles
- Fungus gnats
- Galls on leaves and twigs
- Hemlock woolly adelgid
- Japanese beetles
- Lace bugs
- Leafminers
- Mealybugs
- Pine sawflies
- Root aphids
- Root-knot nematodes
- Russet mites
- Sapsucker damage
- Scale insects
- Shore flies
- Slugs and snails
- Spider mites
- Spongy moth (gypsy moth)
- Spotted lanternfly
- Squash bugs and stink bugs
- Squash vine borer
- Tent caterpillars and fall webworm
- Thrips
- Whiteflies
- Wood borers