To get rid of spider mites on cannabis, act fast: spray the undersides of leaves with insecticidal soap or neem in veg, repeat every 3 days to break the egg cycle, and drop the room to cooler temperatures with higher humidity, which mites hate. Fine webbing and tiny yellow stipple dots mean an active infestation.
How to know you have spider mites
Spider mites are tiny, often smaller than a pinhead, and they live on the undersides of leaves where you rarely look. The first sign most growers notice is stippling: fine yellow or white speckles across the leaf top, where mites have pierced cells and drained them. Flip a leaf and you may see the mites themselves, plus their eggs, as specks that move if you watch closely. As the infestation grows, you get fine silk webbing strung between leaves and along stems. By the webbing stage, populations are already large.
Mites explode in hot, dry rooms. High temperatures speed up their breeding cycle dramatically, so a warm, low-humidity tent is a mite paradise. That environmental angle is also one of your best weapons.
Move fast, they breed fast
The reason spider mites get out of control is speed. In warm conditions a female can lay eggs that hatch within days, and those offspring mature and lay their own eggs quickly. A handful of mites becomes thousands in a couple of weeks. That is why a single spray never finishes the job: it may kill adults but leave eggs that hatch two or three days later. You have to treat repeatedly on a tight schedule to catch each new hatch before it can breed.
Treatment schedule
- Isolate the affected plant if you can, and inspect every other plant, since mites spread by walking and on your hands and clothes.
- Spray thoroughly, hitting the undersides of leaves where mites and eggs live. In veg, insecticidal soap or neem oil are common choices; some growers rotate products so mites do not adapt.
- Repeat every 2 to 3 days for at least three to four cycles to catch newly hatched mites before they lay eggs.
- Lower the room temperature and raise humidity a bit, since mites favor hot and dry. Cooler, more humid conditions slow their breeding.
- Keep inspecting leaf undersides after you think they are gone; mites are famous for coming back from a few survivors.
Avoid spraying oils or soaps on flowering buds. Late-flower mite problems are hard, which is one more reason to catch them in veg.
Signs at a glance
| Sign | Stage of infestation |
|---|---|
| Fine yellow or white stippling on leaf tops | Early, act now |
| Tiny moving specks on leaf undersides | Active feeding |
| Clusters of eggs under leaves | Breeding, tighten spray schedule |
| Fine silk webbing on leaves and stems | Heavy infestation |
| Leaves bronzing and dropping | Severe, plant health at risk |
Keeping them out for good
Prevention beats eradication every time. Quarantine new plants before they join your garden, since mites often hitchhike in on infested clones. Keep the room cooler and reasonably humid rather than hot and bone dry, which discourages mites from the start; our temperature and humidity guide covers target ranges. Keep the space clean, avoid tracking mites in on clothing after visiting other gardens, and scout leaf undersides regularly with a loupe. Steady airflow and a healthy, unstressed canopy also make plants less inviting. Starting with clean, nursery-grown stock removes the most common way mites enter a room in the first place.
Frequently asked questions
Why do spider mites keep coming back after I spray?
Because most sprays kill adults but not eggs. Those eggs hatch two to three days later and the cycle restarts. You need to repeat treatment every 2 to 3 days for several cycles to catch each new hatch before it breeds. Skipping a treatment lets the survivors rebuild the population quickly.
What environment discourages spider mites?
Mites love hot, dry rooms because heat speeds their breeding. Cooler temperatures with moderately higher humidity slow them down significantly. Pairing an environmental shift with your spray schedule is far more effective than spraying alone, and it makes your grow less inviting to mites in the first place.
Can I spray for mites during flowering?
Avoid spraying oils and soaps onto buds, since residue and mold risk make it a bad idea. Late-flower mite control is limited mostly to environmental measures and careful removal of the worst leaves. This is exactly why catching mites in veg matters so much, when you can treat aggressively without touching flower.
How did spider mites get into my grow?
Most often they ride in on infested clones or on your clothing and hands after contact with another garden. Pets and open windows can bring them too. Quarantine every new plant, inspect leaf undersides before introducing it, and start with clean nursery stock to cut off the most common entry route.
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