Aphids reproduce rapidly and gather in colonies on tender shoots, stems and the undersides of leaves. Adults and nymphs pierce plant tissue and suck sap, causing leaves to curl, yellow or become distorted when populations are high. They excrete sticky honeydew that can encourage black sooty mold. Some aphid species also transmit plant viruses as they move between plants. Lady beetles, lacewings, hoverfly larvae and parasitic wasps often keep populations under control naturally.

How to Fix It
Water spray: Knock aphids from plants with a firm stream of water, concentrating on leaf undersides and tender new growth.
Remove heavily infested growth: Pinch off badly colonized leaves or shoots when practical.
Control weeds: Remove nearby weeds that can harbour aphids and provide alternative hosts.
Encourage beneficial insects: Protect lady beetles, lacewings, hoverflies and parasitic wasps by avoiding broad-spectrum insecticides.
Insecticidal soap: Spray aphids directly, including those hiding beneath leaves. Soap works by contact, so complete coverage matters.
Neem: Neem-based products containing azadirachtin can suppress aphids and interfere with feeding and development.
Horticultural oil: Horticultural oils can control exposed aphids by contact. Thorough coverage is essential.