Spider Mites: How to Identify and Kill Them (14-Day Rescue Plan)

July 12, 2026

Found speckled leaves or — worse — webbing? Don't panic, but don't sleep on it either: in a warm grow tent spider mites double their numbers roughly every 4 days. Here's the identification check, then the 14-day plan that actually clears them (hint: one spray never works).

Identify The 14-day plan What to spray Prevention

First: confirm it's spider mites

The 10-second loupe test

Flip a speckled leaf and look at the underside with a loupe or phone macro lens. Moving dots with 8 legs = spider mites. Silvery smears and black specks = thrips (different treatment — see our thrip control range).

The 14-day rescue plan

When	Action	Detail
Day 0	Isolate & assess	Quarantine the plant (or treat the whole tent — if one plant has them, assume all do). Prune off heavily webbed growth into a sealed bag. Wipe down tent walls, pots and drip trays.
Day 0 (evening)	First spray — lights off	Coat every leaf, especially the UNDERSIDES, until run-off. Spray at lights-off or dim light to avoid leaf scorch. Get the tops of pots and the stem base too.
Day 3	Spray again	This is the one everyone skips — and it's why they fail. Eggs laid before spray 1 have now hatched; kill the new generation before it can lay.
Day 6 & 9	Sprays 3 and 4, rotate products	Rotate between two different sprays (e.g. SMC and SB Plant Invigorator) so nothing survives to breed resistance.
Day 12+	Monitor & protect	Loupe-check leaf undersides twice a week. Keep humidity up around 55–60% in veg (mites love hot and dry), and switch to a preventative like Skram.

Why 4 sprays, not 1

No spray on the market kills mite eggs reliably. Eggs hatch 3–5 days after laying — so sprays on days 0, 3, 6 and 9 catch every generation as it hatches, before it can lay. Miss the day-3 spray and you're back to square one by day 7.

What to spray

Rotate between two of these so resistance never gets a foothold. All available for next-day delivery — because with mites, tomorrow matters:

SMC Spidermite Control

from £19.95

Natural knockdown spray — safe through flower

SB Plant Invigorator

from £6.95

Physical-action spray + growth stimulant, zero resistance

Guard 'n' Aid For Spider Mite

£11.95

Fast contact killer — rotate it in

Spidermite Protection Spray

£10.95

Ready-to-use bottle for spot treatment

Prevention: never again

Mites arrive on clothes, pets, tools and cuttings — and they thrive when it's hot, dry and still. Make your tent hostile: keep veg humidity around 55–60%, keep air moving with a circulation fan, quarantine any new cuttings for a week, and never go garden → grow room without changing. Then run a preventative through veg:

Maven Skram

from £24.95

Preventative barrier — mites never settle

Athena IPM

from £39.95

Pro-grade integrated pest management

Yellow Sticky Traps x6

£5.95

Early warning for flying pests

C-Hellfire

£24.95

Heavy-infestation option

Shop All Spider Mite Control

Quick answers

How do I know it's spider mites and not something else?

Three signs together: pale speckling ('stippling') on the tops of leaves, tiny slow-moving dots on the undersides (use a loupe — 8 legs, reddish-brown or translucent), and in bad cases fine silk webbing over growing tips. Thrips leave silvery smears instead; fungus gnats are flies in the coco, not on leaves.

How fast do spider mites spread?

Terrifyingly fast in grow-tent conditions. At 27 °C+ a mite goes from egg to egg-laying adult in about a week, and each female lays over 100 eggs. That's why a couple of speckled leaves becomes a webbed-up plant within a fortnight — and why you treat the day you spot them.

Can I spray during flowering?

Early flower, yes — use gentle physical-action products like SMC or SB Plant Invigorator and spray at lights-off. Late flower, avoid soaking the flowers themselves: spot-treat, prune the worst, keep airflow high, and lean on climate control rather than sprays.

Why do the mites keep coming back after I spray?

Two reasons: sprays don't kill eggs (so a single spray always fails — you must repeat every 3 days, 3–4 times), and re-infection from the environment — unwashed tent walls, tools, clothes, or a pet wandering between the garden and the grow room.

How do I stop them coming back for good?

Hygiene plus hostile climate: don't enter the tent straight from the garden, wash hands and wear indoor-only clothes, wipe the tent down between grows, keep veg humidity 55–60%, and run a preventative like Maven Skram or Athena IPM through veg. Sticky traps by the intake give you early warning of anything flying in.