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Leaf Septoria On Marijuana Plants

Leaf Septoria On Marijuana Plants

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


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Comment Section

31 thoughts on “Leaf Septoria On Marijuana Plants

By Flintz on 26 February 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?

By sean on 4 June 2017

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

By BlueDuck on 8 July 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!

By Kyle Sacker on 24 June 2015

ive used grow clean for this too!!! worked great!!

By Rinnie on 21 September 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 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?!?!

By latewood on 23 September 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 future grows.

By Jeff arnold on 29 March 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 have been in fox farm dirt and feed fox farm since feeding started could this be because of the different weed I'm growing.

By latewood.ILGM on 30 March 2016


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. 🙂

By Tim on 7 June 2016

Heavy buds making my branches lean down any suggestions

By tommy on 7 September 2016

Stake cage or trellis

By Jamie1234 on 5 April 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

By ballsnall on 8 July 2018

Tie them up, use a net or hooks in the ceiling

By Corey on 3 July 2016

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

By Sharon on 11 August 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.

By Half Moon Green Trees on 9 November 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 will show signs of "Yellow Leaf Spot", even in an indoor environment.

By Anahid on 20 March 2017

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

By sean on 4 June 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% 😀😀.

By Kyle on 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.

By Cannubis on 10 June 2017

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

By harvey hutter on 3 September 2017

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

By Roy ILGM on 4 September 2017

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

By Cannubis on 3 September 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 caused through root uptake of bacteria or mold spores" NO


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

By sheshe on 8 July 2018

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

By Sharon Riggan on 11 August 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 other things. We hear it's an epic year for this out west this year.

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