# Round brown spots with yellow halos on lower leaves: likely causes and fixes

> Round brown spots with yellow halos on lower leaves on cannabis is most often Septoria leaf spot. How to tell them apart, the fix for each and what recovery looks like.

Also called: leaf spot, brown spots yellow ring, target spots, septoria, yellow leaf spot.

Run the checker with this sign: https://genetixbay.com/knowledge/diagnose/?at=old&s=spots-yellow-halo

## Likely causes, most likely first

### Septoria leaf spot (Possible)

- Kind: Disease; urgency: Deal with it this week
- Fix: Mainly outdoor and greenhouse. Strip infected lower leaves into a bag, keep foliage dry (water at the base), mulch to stop splash, open the lower canopy, clear debris; protectants only where registered.
- Recovery: Spots stop climbing within 1-2 weeks.
- Confirm: Send a sample to a plant diagnostic lab: For rots, wilts, leaf spots and viruses you can't separate by eye, send a fresh sample (whole plant with roots or a wilting branch with healthy and diseased tissue) in a sealed bag to a university or commercial plant diagnostic clinic. Results in days to 2 weeks.
- Confirm: Magnifier check of leaf undersides and new growth: Use a 10-20x loupe for spider mites, thrips, aphids and whiteflies, and a 30-60x lens or clip-on phone macro for broad and russet mites. Check the undersides of 10 affected leaves across several plants and the newest shoot tips, in white light. Look for moving dots, eggs, shed skins, webbing, slender insects with black specks, and glassy specks on new growth.
- Article: [Septoria leaf spot (yellow leaf spot) in cannabis](https://genetixbay.com/knowledge/diseases/septoria-leaf-spot.md)

## Note

Guidance, not a guarantee. The checker weighs common causes against what you tell it; confirm with the tests before you treat, change one thing at a time and watch the new growth.