QUICK ANSWER
A sticky film on leaves — especially new growth that’s curling — is the classic sign of aphids. They’re small, soft-bodied insects that cluster on stems and the undersides of leaves, and that stickiness is honeydew, a sugary residue they leave behind while feeding.
Why this Happens
Aphids feed by piercing plant tissue and drawing out sap, concentrating on tender new growth where it’s easiest to access. As they feed, they excrete honeydew — the sticky residue you’re noticing — which can also attract ants and, given enough time, develop into black sooty mold on the leaf surface below. Curling new leaves are a direct result of the feeding damage itself, not a separate problem.
Aphids reproduce fast, so a few missed for a week or two can turn into a real infestation. Catching it early makes the whole process much easier.
How to Fix It This Week
• Blast them off with a strong stream of water — this alone removes a large percentage of an aphid colony and is often enough for a light infestation.
• Follow up with insecticidal soap every 3-5 days until they’re gone, focusing on the undersides of leaves and stem joints where they cluster.
• Check nearby plants too — aphids move easily between plants growing close together.
• Don’t over-fertilize with nitrogen going forward — lush, soft new growth (which heavy nitrogen encourages) is exactly what aphids prefer.
Related Questions
Do I need to worry about the black coating (sooty mold) too?
It usually clears on its own once the aphids feeding above it are gone — sooty mold grows on the honeydew, not the plant itself, so removing the source stops it from spreading further.
Are ants on my plant related to this?
Very likely, yes — ants are drawn to aphid honeydew and will sometimes even protect aphid colonies from predators in exchange for it. Seeing ants is often a clue to check for aphids nearby.
Will insecticidal soap harm beneficial insects like ladybugs?
It can, if sprayed directly on them — apply it directly to the aphids themselves rather than broadly, and avoid spraying open flowers where pollinators are active.
Related: Whiteflies or fungus gnats · Spider mites · Plant Problems & Troubleshooting guide
