Why do my leaves look dull, silvery and finely speckled?

Stippling, silvering and bronzing are the signature of sap-suckers feeding cell by cell — how to tell red spider mite, thrips and leafhopper apart, and what each needs.

Difficulty: intermediate
Time: 20 min
Read: 5 min

Short answer

Turn the leaf over — all three culprits are underneath. Fine webbing at the shoot tips and hot dry conditions means red spider mite. Silvering with tiny black varnish-like specks means thrips. Coarse pale mottling with white cast skins stuck to the underside means leafhopper. All three respond to raising humidity and removing the worst leaves.

This is a different kind of damage from a bite. These insects push a stylet into individual cells and empty them, so each feeding point leaves one pale dot. Thousands of them turn a leaf dusty, then silvery, then dull bronze, and by the time it is obvious across a plant the population has been building for weeks.

Stippling, silvering and bronzing — reading sap-sucker damage

Step by step

Look at the leaf against the light, tilted.Early stippling is very hard to see straight on and obvious at an angle. It looks sand-blasted — a scatter of pale pinpoints, each one an emptied cell — and it is the first stage of all three problems.
Turn the leaf over and use a lens.Red spider mites are barely visible moving dots, often reddish or yellowish, with very fine webbing at the shoot tips and leaf junctions in a bad infestation. Thrips are slim, elongated, fast, and drop when disturbed. Leafhopper nymphs are pale, wedge-shaped, and scuttle sideways.
Look for the black specks that identify thrips.Thrips leave tiny black varnish-like drops of excrement on the silvered areas. Nothing else does. Combined with silvering and distorted, flecked flower petals, that is a confident identification.
Look for the white cast skins that identify leafhopper.Empty white skins stuck firmly to the underside of the leaf, and adults that jump or fly off when the plant is touched. Common on roses, rhododendron, primula and in greenhouses.
Check the conditions, which tell you as much as the insect.Red spider mite explodes in hot, dry, still air — a conservatory, a greenhouse in July, a houseplant next to a radiator. Thrips also prefer hot dry conditions. Both are far less of a problem in a humid, well-ventilated position.
Tap the plant over white paper.A sheet of white paper held under a shoot, tapped sharply, catches thrips and mites that are otherwise invisible. Watch for a few seconds; movement is what gives them away.
Raise the humidity and wash the plant.For mite and thrips indoors and under glass this is genuinely effective. Shower the plant thoroughly including every leaf underside, group plants together, stand pots on damp gravel, and damp down a greenhouse floor in hot weather.
Remove the worst leaves and improve airflow.Take off leaves that are already bronzed — they will not recover and they hold the largest populations. Space plants so air moves between them, and ventilate glass in warm weather.
Use biological control under glass.Predatory mites for red spider mite, and predatory mites or nematodes for thrips, work well in the enclosed warm conditions of a greenhouse or conservatory. They need to be introduced early, before the population is large, and they cannot be combined with a broad-spectrum spray.
Rule out the look-alikes if nothing is there.Silvering with no insects at all can be sun scorch, hard-water spotting on hairy leaves, or, on plums and cherries, silver leaf disease — which affects whole branches, shows a purple-brown stain in cut wood, and is a serious tree disease rather than a pest.

Tips

Red spider mite thrives on plants that are dry at the roots, so proper watering is part of the control rather than a separate issue.
A leaf that has bronzed is finished — judge whether treatment is working by whether new leaves come out clean.
Thrips damage on flowers often shows before the leaves: pale flecks and streaks on petals, and buds that open distorted.
Do not treat conifer needles browning from the inside as mite damage automatically; conifers shed inner needles naturally every autumn.

Common mistakes

Treating stippling as a nutrient problem and feeding — Feeding does nothing to the insects and the extra soft growth is exactly what they prefer.
Only spraying the top of the leaf — Every one of these lives underneath. A contact treatment that misses the underside misses the entire population.
Introducing biological controls after spraying — Residues kill the predators. Once you have sprayed, wait as long as the label states before releasing anything.

If it doesn't work

Fine pale stippling, very fine webbing at shoot tips, hot dry position

Cause: Red spider mite — Fix: Shower the plant, raise humidity, ventilate, remove bronzed leaves, and use predatory mites under glass.

Silvery patches with tiny black varnish specks, flecked petals

Cause: Thrips — Fix: Blue sticky traps to monitor, remove badly affected leaves and flowers, raise humidity, biological control under glass.

Coarse pale mottle, white cast skins underneath, insects that jump

Cause: Leafhopper — Fix: Largely cosmetic outdoors. Wash the undersides, tolerate it on established shrubs, and check roses and rhododendron in warm summers.

Silvery sheen on whole branches of a plum or cherry, purple stain in the cut wood

Cause: Silver leaf disease, not a pest — Fix: Cut affected branches back well into clean wood in summer, in dry weather, and never prune stone fruit in winter.

Questions people ask

Are these mites the same as the red spiders I see on walls?

No. The bright red mites running over paving and walls in summer are harmless predatory or algae-feeding mites. Red spider mite on plants is much smaller, lives on leaf undersides and is usually not red at all in summer.

Will the silvered leaves go green again?

No. The cells are empty. New growth after the pest is controlled comes out normal, and that is the only measure of success.

Does washing really work?

On mites, yes — a thorough shower removes a large proportion mechanically and raises humidity, which suppresses breeding. It has to be repeated every few days to break the cycle.