Leaf Septoria on marijuana plants

Reading time: 6 minutes

Yellow leaf spot, also known as leaf septoria, are caused by Septoria cannabis and S. neocannabina.

These are fungal pathogens aimed specifically at marijuana plants.

It is brought about by warm weather and rain and effect marijuana grown outdoors.

It may also show up in nitrogen- deficient plants. Read this article and learn how to identify and treat yellow leaf spot.

Signs of leaf septoria

Yellow leaf spot initially shows up on the lower leaves of your plant.

These spots may vary in shade from white to a grayish brown to yellow, initially displaying little circular lesions.

Once it starts to grow it starts looking like a bump and its size continues to increase.

Signs of leaf septoria marijuana plant
Signs of leaf septoria cannabis plant

Yellow leaf spot will harm the leaves and often times the stems of the plant, although it won’t cause the crop to die off.

Want to make sure that you give your plants the best protection? I have created three various bottles to counter most diseases or pest in order to fight back!

Marijuana plant protector

Bergman’s Plant Protector

  • Protect your plants from diseases and harmful pests.
  • Consists of three 20 ml bottles
  • Enough plant protection system supplies for up to 20 plants
  • Suitable for soil, hydroponic and all other grow mediums

If for any reason this is not properly cared for it will lessen the marijuana plant’s yield.

The affected leaves will become dry where the spot is and overtime break and produce a hole at the point where the spot started off.

How to avoid and cure leaf septoria

The most affected leaves will become totally yellow, dry out and fall off.

You will want to get rid of the leaves that fell off or else you will end up with a landing turf for spores to overwinter.

Basically, they will hide out until the weather warms up and then that’s when they will wreak havoc.

Yellow leaf spot spores do their dirty work through traveling by water, wind and clinging on to things that pass by.

How to avoid and cure leaf septoria on marijuana plant
How to avoid and cure leaf septoria

You can avoid the damage yellow leaf spot causes your plants through crop rotation.

Basically, after every harvest you will pick a new location to plant.

If you are not able to do this, then after harvest, completely get rid of all leftovers from the last vegetation and till the soil really good to make sure all remains are gone.

Get the location ready using sterilized compost and mix it well into the soil.

Doing this will give the new crop plenty of nitrogen to provide a good, strong start.

If you don’t have any ready compost, you can mix in blood meal, fish meal or soybean meal to the dirt that is already there.

Therefore, you will be certain to have all the necessary nitrogen for your plant.

Make sure you proper disinfect any tools you used with rubbing alcohol or peroxide prior to putting them away.

Not sure if your plants suffer leaf septoria? Also read Symptom checker – Identify marijuana plant problems

Correct Nutrients

If you want to make sure that you give you plants the highest chance on getting the proper nutrients, or to prevent nutrient issues in in the first place, I have created a perfectly balanced fertilizer kit, ready to use for all marijuana plants!

Bergman’s fertilizer kit

  • Enough nutrients for at least 5 plants
  • All the nutrients from seedling to harvest
  • Usable for all marijuana plants
  • Suitable for soil, hydroponic and other growing mediums

One more thing you can try when beginning a new marijuana bed is adding a fungicide to the planting location prior to putting the seedlings and seeds there.

You have the option to buy one of the many natural solutions pre-made (at this link here) or you can make your own.

Applying helpful bacteria, like Bacillus Pumilis or a good fungi like Trichoderma will help the soil if you don’t have any compost to use.

Also, you may try spraying the site with essential oil combinations with cinnamon, coriander, neem, sesame or clove.

Fine misting the soil with compost tea or even baking soda will aid in avoiding yellow leaf spot spores from making a home at your site.

Download my free Grow Bible to learn how to grow strong and healthy plants!

Marijuana plant symptoms

  • White/grayish brown/yellow spots on leaves
  • Circular lesions on lower leaves
  • A small pimple-looking bump
  • Leaves dry and fall off
Leaf septoria symptoms marijuana plant
Leaf septoria symptoms cannabis plant

Remember to water your plants early morning or early evening time. Never water the leaves, only the soil.

By doing this, the sunlight will not burn the leaves.

Again, if your plants get infected by yellow leaf spot, it is important to always remove and completely destroy all affected leaves.

If you don’t do this, you will most likely regret it.

Affected leaves still contain the problem and can come back to haunt you because yellow leaf spot easily clings on to things and travels from one destination to the next.

Using the correct nutrients and plant protector will get you a long way and your plants will have less chance of getting sick, in addition of being less vulnerable for pests and diseases. I have created multiple grow sets which features all you need in order to grow healthy plants from seed to harvest!

Buy your grow set

FAQ about leaf septoria

How do you treat septoria leaves on Cannabis plants?

You can avoid the damage yellow leaf spot causes your plants through crop rotation.

What causes septoria leaf spot?

Septoria leaf spot is caused by a fungus, Septoria lycopersici.

How does Septoria leaf spot spread?

Septoria Leaf Spot is a fungus and spreads by spores. As with other fungal disease, it establishes and spreads most rapidly in wet or humid weather

Have you ever grown marijuana plants that developed leaf septoria? Do you have other tips on treating or preventing it?

Please share your experience with us in the comments!

Happy growing!


Avatar for Robert Bergman

Robert Bergman

Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations. His passion for growing led him to develop his own Gold Leaf strain. Now, Robert is dedicated to sharing his knowledge with the world.... [Read full bio]

  • Pinterest

44 comments on “Leaf Septoria on marijuana plants”

  1. Keep clipping the leaves off that have the fungus on them and spray plant with water and peroxide mix, the buds are usually not effected by septoria

  2. First i carefully cut all affected leaves off my plants and bagged them up. Be sure to wear gloves. I used 1 cup of peroxide to 1 gallon od distilled water and 1 tablespoon of castile soap and Sprayed all of my plants. I will be Repeating in 3-5 days. So far the spread has slowed down. At least im not loosing 10-20 a day.
    If you suspect that you may have a fungus, be Sure to Wear gloves and don’t touch other plants.

  3. This is the first year I’ve ever experienced this stuff I have five or six plants I’ve trimmed off leaves as it shows and I’m still getting more and more I’m afraid if I take off too many leaves it’s going to screw up my plant, is this so, or should I keep clipping them off as they show up

  4. next time try to employ light stress training to your plants by twisting the steam as it grows during the vegetative stage. This will cause the plan to build stronger roots. Keep doing this until you have the thickness you want, then flip to flower.

  5. Id also like information on how to apply the cinnamon to keep the few leaves I have showing spots from spreading

  6. Jen, This would be the best for you since we are not set up for Q and A here in the blog. I Suggest You Go Here: Support.Ilovegrowingmarijuana.Com Our Members And Staff Can Take A Look At Your Pictures And Give You Informed Advice.

  7. Did you use the Final Stop, and did it work? We are thinking about using it, along with Root Drench and Green Cure (sodium bicarbonate). Our plants are fine, but grow next to a garden with this problem.

  8. Our local sources say peroxide and root drench on the soil to kill the spores, neem oil on the plant; we are looking at using Dr. Earth Final Stop — it got rid of our leaf miners and a few other things. We hear it’s an epic year for this out west this year.

  9. mine have round white spots, about as big around as a pencil eraser..any ideas as to why? (indoor grow)

  10. Robert What Is The CURE for LEAF SEPTORIA??? My outdoor plants have it NOW!!!

  11. In the future, use a straw cut straight down and cut the lent you need, heard it works. I haven’t tried it yet

  12. a number of points:
    * Don’t use baking soda; use /Potassium/ bicarbonate (Green Cure).(to treat an infection). Use it every few weeks as nes lesions show up.
    * Cinnamon? References?
    * different weed? no
    * “leaf septoria can actually be caused through root uptake of bacteria or mold spores” NO

  13. I have a severe case of yellow leaf. I am using copper fungicide to help any other suggfestions?

  14. Can you give me more info on how to treat with cinnamon? Would that be to sprinkle cinnamon on the plants, or to mix with water. Thanks!

  15. If you said anything about curing the problem (on an infected plant – not for the next planting) I coudn’t find it.

  16. Mine to , I’ve had a 99% germination rate with fifty wwa seeds and five crystals every one accept for one Didn’t crack. 99.9% .

  17. You can use a little cinnamon, it will stop the spores and fungus knats won’t stick around either!

  18. My leaf on my weed plant are getting yellow spot on the how can i stop it fast please let me know very soon.

  19. Thanks Robert for all the good tips you provide; every one of the seeds I got from you have germinated so far.

  20. Hey Jeff,

    The leaf septoria can actually be caused through root uptake of bacteria or mold spores, this can happen when using water or nutrient that is not properly sanitized, or algae, after enough exposure to the roots the leafs will show signs of “Yellow Leaf Spot”, even in an indoor environment.

  21. Will dr. Earth final stop natural and organic Disease Control fungicide Work for spores know as brown spots on my marijuana plants

  22. Jeff,

    The most common reason for yellowing of leaves on young plants is over watering them. Maintaining a proper PH is also very important in order to allow the plant to uptake the full scale of minerals it needs to thrive. 🙂

  23. Have 13 plants and 2 only showing yellowing on some leafs not sure what kind of weed it is all from seed from female med weed I have smoked over the last year they are very good looking plants THat have been in fox farm dirt and feed fox farm since feeding started could this be because of the different weed I’m growing.

  24. […] Despite the fact that it isn’t usually lethal, yellow leaf spot can heavily inhibit the growth of the plant and its eventual yield. You can prevent yellow leaf spot by keeping the soil well-aerated and applying a fungicidal  compound to your compost. If you still have trouble with yellow leaf spot, you can apply baking soda as a reactive measure. Read more about Leaf septoria on marijuana plants […]

  25. Sorry to hear about your issue. At this point, there is not much that you can do. My advice to you, would be to join our support forum, and post there. This will be a great help to you for future grows.

  26. The article on leaf septoria is very good. However, there is little info on how to get rid of septoria once I have it. I’m now well prepared for next years crop with the soil preparation info.
    I have sprayed baking powder solutions as well as neem oil as directed in the articl but to no avail. I have several “quarter” sized buds that look healthy and green. I’m afraid my leaves are going to die off and leave my buds lacking in growth potential.
    Any advice?!?!

  27. […] Despite the fact that it isn’t usually lethal, yellow leaf spot can heavily inhibit the growth of the plant and its eventual yield. You can prevent yellow leaf spot by keeping the soil well-aerated and applying a fungicidal compound to your compost. If you still have trouble with yellow leaf spot, you can apply baking soda as a reactive measure. Read more about Leaf septoria on marijuana plants […]

  28. I’m having these yellow leaf issues now, I have some blood
    meal and I’m wondering if I add it to my organic soil, will it help with ridding my plants of the yellow leaf problems?