Plant Problem Diagnostic
Aphids in the Garden
The short answer
Aphids are small soft-bodied insects that cluster on tender new growth and leaf undersides, sucking sap and leaving sticky honeydew. Most aphid damage is superficial, and control is often unnecessary because natural enemies keep populations in check, so the first step is to tolerate and monitor.
For mild populations, knock aphids off with a strong spray of water from the hose or squish them. For heavier infestations, insecticidal soap, which contacts and dehydrates the insects and loses toxicity once dry, is among the least-toxic options. Reserve stronger measures for plants that are truly failing.
How to identify it
Aphids are usually light green but may be black, gray, red, or fuzzy, and gather in dense groups on the undersides of leaves and on new shoots. Signs include curled or distorted leaves, sticky honeydew, and sometimes black sooty mold growing on the honeydew. Ants tending aphids are another clue.
- Small soft-bodied insects in clusters on new growth and leaf undersides
- Sticky honeydew and possible black sooty mold
- Curled or distorted leaves
- Attended by ants in many cases
IPM least-toxic management
- 1Monitor and tolerate — Check leaf undersides regularly; since damage is often superficial and natural enemies help, treatment may not be needed unless plants are failing.
- 2Wash them off — Dislodge mild populations with a strong spray of water from the hose, or squish colonies by hand.
- 3Protect beneficials — Encourage lady beetles, lacewings, and other natural enemies; avoid broad sprays that kill them along with aphids.
- 4Use insecticidal soap if needed — For moderate infestations, apply insecticidal soap so it directly contacts the aphids; it works by contact and loses toxicity once dry.
When to escalate
If aphids persist on a valuable plant despite washing and soap, or if a virus or heavy honeydew is causing decline, seek guidance. For product options beyond least-toxic categories, consult your county Extension and always follow the label.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- University of Minnesota Extension — Aphids in home yards and gardens — Aphids cluster on leaf undersides and produce honeydew; monitoring, washing off with water, and insecticidal soap are recommended, and control is often unnecessary.
- Oregon State University Extension — Keep aphids under control with low-risk strategies — Most aphid damage is superficial, natural enemies keep populations down, and unless plants are failing or honeydew is a problem, control is not necessary.