Pests

Aphids

Also called: greenfly, blackfly

Soft pear-shaped insects clustered on tender new growth and flower buds, multiplying by the day.

What you'd see

Clusters of green, black, pink or white insects on new shoots and under young leaves
Curling, puckered new leaves
Sticky honeydew; white cast skins that look like dandruff
Ants farming them on plants that summer outdoors

Where to look

Soft new growth, flower stalks, and the undersides of the youngest leaves.

How it spreads

Females give live birth to clones without mating; winged forms appear when crowded and fly to new plants.

Is it really this? Look-alikes

Mealybugs — Mealybugs are waxy and slow in leaf joints; aphids are smooth-bodied and cluster on tips.
Thrips larvae — Thrips larvae are slender and solitary; aphids are plump and crowded.

What's going on

Aphids drink sugary sap from phloem and excrete the excess as honeydew. Soft, nitrogen-rich new growth is the easiest to pierce, which is why they concentrate on tips.

Their clone-by-live-birth reproduction means a lone aphid becomes hundreds in two weeks.

Why?

Because aphids are soft and slow, they are the easiest pest to remove physically. The lesson is speed: act the day you see them and you rarely need anything stronger than water and your fingers.

Grandmother's remedies

What people have always done — with an honest note on each.

Finger squash and rinse
Run thumb and finger along the shoot, then rinse under the tap.
Verdict: Completely effective for small numbers. Grandmothers were right.
Soapy water spray
A teaspoon of soap per litre, sprayed on the colony.
Verdict: Works on contact; repeat every few days for a week.
Garlic or chilli water
Steeped garlic or chilli strained and sprayed.
Verdict: Mild repellent effect; unreliable as a treatment.

Modern remedies

What growers and extension services reach for today.

Insecticidal soap
Spray to run-off on tips and undersides.
Verdict: Effective, quick, safe indoors.
Lacewing larvae or ladybirds
Released on outdoor or conservatory plants.
Verdict: Effective and satisfying; indoors they wander off.

Honest verdict

Aphids are the easiest win in this atlas. If a plant keeps getting them, look at whether you are feeding too much nitrogen or growing it too warm and soft.

Prevention

Check tips weekly during active growth
Feed at half strength
Rinse plants that summer outdoors before bringing them in

Plants this commonly troubles

Fiddle-leaf fig Philodendron