Spider Mites: The Pest That Doubles Every 3 Days
Why Spider Mites Explode in Summer
Spider mites thrive in hot, dry conditions — exactly the environment many indoor spaces become in summer. At 27°C (80°F) or above, they complete a full lifecycle in just 5–7 days. A population can double every 3 days under ideal conditions. Low humidity accelerates this further, which is why a plant that looked fine in spring can be heavily infested within weeks of summer heat setting in.
Identification
Spider mites are 0.4mm — barely visible to the naked eye. The first signs are usually their damage: pale stippling or bronze speckling on the upper leaf surface where they've punctured cells to feed. Fine webbing at leaf junctions or on buds confirms a significant infestation. The quickest test: hold a sheet of white paper under a branch and tap. Tiny moving dots are spider mites.
What Works
Wipe before you spray. Remove webbing and manually dislodge adults with a damp cloth before applying alcohol. Webbing protects mites from spray contact — break it down first.
70% isopropyl alcohol, undersides first. Spider mites live, feed, and lay eggs on the underside of leaves. Spraying only the top surface does almost nothing. Flip every leaf and coat the underside completely, then do the top.
Raise humidity. Mites hate humidity above 60%. A pebble tray, grouping plants, or a humidifier near the plant makes the environment actively hostile to mites. This doesn't replace treatment but significantly slows reinfestation.
Treat every 3–4 days for 5 weeks. The short lifecycle means you need sustained pressure. 5 weeks accounts for the full range of their reproductive cycle across multiple generations.
What People Miss
Neighbouring plants. Spider mites spread by crawling and on air currents. Check every plant within a metre of an infestation. Treat them all even if you can't see mites yet — they're likely there.
The top of the leaf. Damage shows on top, but mites live underneath. It's the most common reason treatments fail: people spray what they see and miss where the pest actually is.
How You Know It's Working
No new webbing. Stippling stops spreading. The newest leaves come in clean. Old stippled leaves don't recover — judge progress by new growth only.