What it is
A mite (related to spiders, not an insect) half a millimeter long, almost invisible to the naked eye. It lives under the leaves, sucks their juices and multiplies at a tremendous rate: in the heat, a new generation every week. It is one of the most feared pests in growing.
How to tell
At first, tiny yellow or white dots on top of the leaves (these are the bites). Turn the leaf over, with a loupe, and you see the bugs and their eggs. Later, fine webs appear between the leaves and the tips: that is already an infestation.
What favors it
Heat and dry air. That is why it shows up a lot in summer and in indoor grows with low humidity.
How to fight it
Potassium soap or neem oil, sprayed especially under the leaves, with the light off, repeating every 3 or 4 days, three times (the eggs don't die with the first one). Raising the humidity a little slows it down. Predatory mites (like phytoseiulus) that eat them are also used. In late flowering it is hard: you can't spray the buds.
How to prevent it
Don't let the air get too dry (the humidifier at 55 % humidity helps) or too hot, and check often with the lens.
▲ Pros
- Caught early it heals almost without damage
▼ Cons
- Untreated it can kill the plant, and in a batch it spreads to the next batches
🎮 Practice it in UnderGrow
Treat it with potassium soap (treat). It is favored by over 27 °C and under 45 % humidity, and a stressed plant gets sick more. At first you only see it with the lens: caught early it barely does any damage; untreated, it grows, spreads and can kill the plant.
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