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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

Signs of leaf septoria weed

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.

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. If for any reason this is not properly cared for it will lessen the marijuana plants 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.

Not sure if your marijuana plants suffer from a yellow leaf spot infection? Check the article Marijuana diseases for a list with pictures of all possible marijuana diseases

How to avoid and cure leaf septoria

Cure yellow leaf spot cannabis

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.

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.

Download my free marijuana grow guide at this link for more growing tips

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.

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.

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

Remember to water your plants early mornings 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 gets 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.

Remember that plants with strong genetics have less change of getting sick and are less vulnerable for pests and diseases. So make sure to buy cannabis seeds from a trusted seed bank.

Thanks for reading. Please leave comments or questions below and don’t forget to download my free grow bible

Robert

31 Comments

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  1. By Flintz

    ,26 Feb 2015
    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?
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    1. By sean

      ,04 Jun 2017
      You can use a little cinnamon, it will stop the spores and fungus knats won’t stick around either!
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      1. By BlueDuck

        ,08 Jul 2017
        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!
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  2. By Kyle Sacker

    ,24 Jun 2015
    ive used grow clean for this too!!! worked great!!
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  3. By Symptom Checker – Identify Marijuana Plant Problems

    ,24 Jul 2015
    […] Leaf septoria […]
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  4. By Diseases on Marijuana Plants, and How to Treat Them | Daily Dank Deals

    ,29 Aug 2015
    […] 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 […]Read More
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  5. By Rinnie

    ,21 Sep 2015
    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 […]Read More
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    1. By latewood

      ,23 Sep 2015
      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 […]Read More
      Was this comment helpful to you?
  6. By Stop Diseases On Marijuana Plants Now!

    ,10 Nov 2015
    […] 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 […]Read More
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  7. By Marijuana Light Leaves Yellow « HempNEWS TV

    ,17 Feb 2016
    […] Stop Leaf Septoria On Marijuana Plants Now! – Leaf Septoria or Yellow Leaf Spot on your cannabis plants? Yellow leaf spot damages the leaves of your marijuana plants but will not kill your crop. Make […]
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  8. By Jeff arnold

    ,29 Mar 2016
    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 […]Read More
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  9. By latewood.ILGM

    ,30 Mar 2016
    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 […]Read More
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  10. By Tim

    ,07 Jun 2016
    Heavy buds making my branches lean down any suggestions
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    1. By tommy

      ,07 Sep 2016
      Stake cage or trellis
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    2. By Jamie1234

      ,05 Apr 2018
      In the future, use a straw cut straight down and cut the lent you need, heard it works. I haven’t tried it yet
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    3. By ballsnall

      ,08 Jul 2018
      Tie them up, use a net or hooks in the ceiling
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  11. By Corey

    ,03 Jul 2016
    Will dr. Earth final stop natural and organic Disease Control fungicide Work for spores know as brown spots on my marijuana plants
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    1. By Sharon

      ,11 Aug 2018
      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.
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  12. By Half Moon Green Trees

    ,09 Nov 2016
    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 […]Read More
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  13. By Anahid

    ,20 Mar 2017
    Thanks Robert for all the good tips you provide; every one of the seeds I got from you have germinated so far.
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      1. By sean

        ,04 Jun 2017
        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% 😀😀.
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  14. By Kyle

    ,30 May 2017
    My leaf on my weed plant are getting yellow spot on the how can i stop it fast please let me know very soon.
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    1. By Roy ILGM

      ,01 Jun 2017
      Hi Kyle, best check our symptom checker guides or post a picture onto the support forum where our experts can help you out. – I❤️GM
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  15. By Cannubis

    ,10 Jun 2017
    If you said anything about curing the problem (on an infected plant – not for the next planting) I coudn’t find it.
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  16. By harvey hutter

    ,03 Sep 2017
    I have a severe case of yellow leaf. I am using copper fungicide to help any other suggfestions?
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    1. By Roy ILGM

      ,04 Sep 2017
      Hi Harvey, your best bet is to put up some pics on the support forum. Our experts will be with you shortly.
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  17. By Cannubis

    ,03 Sep 2017
    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 […]Read More
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  18. By KENNETH SYLVESTER

    ,04 Jul 2018
    Robert What Is The CURE for LEAF SEPTORIA??? My outdoor plants have it NOW!!!
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  19. By sheshe

    ,08 Jul 2018
    mine have round white spots, about as big around as a pencil eraser..any ideas as to why? (indoor grow)
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  20. By Sharon Riggan

    ,11 Aug 2018
    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 […]Read More
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