Aphids
Insect or pest Aphididae · also called plant lice, greenfly, blackfly
Yellow, curled, or mottled leavesSticky leaves or black filmBugs I can see
How to spot it
Tiny soft-bodied insects, green, black, gray, or pink, packed together under leaves and on new shoots. Some have wings. Ants running up and down the stems often mean aphids.
What it does
They suck sap, so leaves curl, pucker, and yellow and new growth is stunted. The sticky honeydew they leave grows black sooty mold. Aphids also spread plant viruses.
What to do now
- Knock them off with a strong spray of water every few days.
- Squash small groups, or snip off the worst leaves.
- Spray insecticidal soap or neem oil on both sides of the leaves, following the label.
- Leave ladybugs, lacewing larvae, and hoverfly larvae alone: they eat aphids by the hundreds.
Keep it away next time
- Go easy on nitrogen fertilizer: soft, fast growth draws aphids.
- Grow alyssum, dill, and yarrow nearby to feed the insects that eat aphids.
- Keep ants off the plants; they guard aphids from their enemies.
- Check the undersides of leaves once a week.
Helpful supplies
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Plants it affects
Every plant in the cabbage family (brassicas), the tomato family (nightshades), the squash family (cucurbits), and the bean and pea family (legumes).
See also
Not sure? Your county extension office can identify it from a photo or sample, often for free.