Pests Spider mites
Fine webbing, yellow speckling
Very fine webbing appears under the leaves, which take on a yellow stippling.
Also called: webbingmitesred spidertiny bugs
Severity
Urgent
Act fast: this can get worse within days.
Parts affected
- Leaves
- Stems
- Flowers
- Fruit
- Roots
- Soil
Family
Pests
From insects to larvae: spot them early to get rid of them fast.
Understand
What is happening inside the plant
Spider mites are arachnids under half a millimetre across that pierce the cells on the underside of leaves and suck out the contents.
Each puncture empties one cell and leaves a pale dot: it is the build-up of those dots that gives the characteristic greyed or bronzed look. They thrive in dry warm air, where a generation completes in a week, which explains how brutal winter outbreaks near a radiator can be. Untreated, the plant becomes webbed over, stops photosynthesising and defoliates within weeks.
Check
How to be sure
Tick what you can see on your plant.
Tick the signs you can see and the gauge will add them up.
Some signs match. If the rest does not fit, look at the related problems further down.
Most of the signs match: this is very likely it. What to do
Signs and causes
What you see, and why
Symptoms
- Very fine yellow speckling on the upper leaf surface
- Fine webbing between stems and under the leaves
- Tiny moving dots visible against the light
- Foliage turning grey, then drying out
Causes
- Dry, warm air, which is ideal for them
- A new plant brought in without quarantine
- Foliage that is never rinsed
What to do
The action plan
In order. Tick each step once it is done.
0/5 done
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Isolate the plant today: they spread fast.
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Shower the whole plant, paying attention to leaf undersides.
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Wipe every leaf with a damp cloth.
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Repeat every three days for two weeks, one full life cycle.
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Cut off the worst-affected parts rather than trying to save them.
Prevent
Stopping it coming back
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Raise the humidity: they avoid damp air.
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Quarantine every new plant for two weeks.
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Inspect leaf undersides once a month.
Questions
Common questions
Why are they called spider mites?
For their webbing and their eight legs: they are arachnids, not insects. That is why most products sold as insecticides do not touch them.
Is a shower enough?
It knocks off a large part of the population, but it has to be repeated every three days for two weeks, while the eggs hatch. One shower on its own settles nothing.
How do I stop them coming back?
By raising the humidity around the plant and checking leaf undersides once a week. Spider mites hate damp.
Keep an eye on it Clusters on new growth
Small pear-shaped insects, usually clustered on new growth.
Causes and fixes
Keep an eye on it Silvery streaking
Tiny insects leaving silvery streaks and black specks on the leaves.
Causes and fixes
Keep an eye on it Cloud of white insects
A cloud of white insects takes off when you shake the plant.
Causes and fixes