Septoria Cannabis

Aloha, I’m a medical grower on the Big Island of Hawaii. I live on the wet side of the island and grow in a 2-greenhouse system, veg and bloom. I have had a severe septoria cannabis issue for the past 1.5 years. I keep my growing area as clean as possible and do a deep clean with soap and bleach in between each round. I keep my pots off the ground using a pallet and plywood floor in my veg house and a full linoleum floor in my bloom house. My bloom greenhouse is especially well ventilated with exhaust fans and oscillating fans. I also use a propane CO2 generator. I always use fresh grow media, promptly remove damaged leaves and prune my plants. I have tried many types of fungicides, both foliar and as a soil drench. My current regimen begins in early veg with soil drenches of Regalia bio-fungicide, which I apply in rotation with feeding, 1 soil drench to full saturation, leave until soil is dry, then 1 feeding with Advanced Nutrients Connoisseur Master Grower nutrient system. I continue this into early flower. I also use foliar sprays in 2 to 3 day intervals alternating my insecticide mix consisting of 70% neem extract, Monterey spinosad and a Yucca-based wetting agent, followed by Monterey LiquiCop fungicide, followed by Organocide Plant Doctor. This system was designed based on the best information I could get from local grow shops. This has not been effective. I am concerned that, in cloning my plants, I am perpetuating the problem as the cuttings are already infected. I am also concerned that my plant-training system also plays a role. I super crop and lollipop to create a flat top and the greatest number of flowering nodes, but this also damages and stresses the plant, which may invite infection. At this point, the only thing I can think of to do is to destroy all of my strains that I have worked for years to find and cultivate, scrub everything carefully with bleach and start again from seed. Unfortunately, this will cause me to have to skip a crop, which is expensive, and then go through all the work to find strains that will grow well in this environment and then find the best phenotype of each strain, which, in my experience, will take at least a year. Do you know of any way to completely eliminate the infection during the cloning or early veg stages? Or, if I have to shut down and restart from seed, how I can prevent the new strains from becoming infected? Honestly, I don’t know if starting over from seed will solve the problem either as the fungus is widespread in the environment here and I have no way to tell how much the problem is caused by cloning infected cuttings and how much is due to environmental exposure. Any help or insight you can provide would be greatly appreciated. Mahalo nui loa.


Welcome to this forum, you’ll discover plenty of great people here. I can’t help with your problems, being new to this, but I’ll invite a few people I think could help…
What do you think @devjyarn, @MK3_Pharms, @hoppiefrog?


Try sulpher or copper based fungicides. Also make sure you are clean.
Check your Soil pH
Everything els seems right


Also try adding azomite to your soil blend your macro might be out of line

I already use Monterey LiquiCop, which is a copper-based fungicide. Advanced Nutrients are advertised as automatically ph adjusting to 6.2, but I also check the ph at every feeding and adjust to between 6.0 and 6.2. I use a mix of Promix BX and perlite at a 3:2 ratio and add Advanced Nutrients Voodoo Juice, Tarantula and Pirhanna benificial microbe and fungus supplements. I have not tried a sulfur-based fungicide as I have not found one that is in liquid form and is easy to apply. However, I have also used Green Cure potassium bicarbonate fungicide and Plant Doctor phosphorus acid systemic fungicide without success.


Is this happening no matter what strain?

Yes, all strains. I currently grow Blue Dream, Cali Trainwreck, OG Kush, Mandarin Kush, Gorilla Glue #4, Royal Queen Critical and Jawa Pie. All strains show the same level of infection. And these are the most resistant of the 25-30 strains I have tried.

Try fungonil or daconil
By chance do you have a vegetable garden or anyone relatively close to.your home. This stuff can travel like very long distances

Thanks for the advice. I’ll look into fungonil and daconil. As far as the local environment, which, of course, I can’t control, I am on a 4 acre parcel that has been cleared. The nearest neighbor is about 250 yards away. I don’t have a vegetable garden, but I don’t know about the neighbors. Neighbors near me also have issues with septoria but not as severe as I have here. As far as I know, this fungus is very widespread here as we are in a tropical rain-forest that has typical humidity above 80% and we get about 200 inches of rain per year.

Welcome @ericm and greetings from the mainland! Do you have an option to put a dehumidifier in your grow? Do you know what your RH% is measuring out at? It definitely sounds like it’s a humidity issue that’s causing it. The other thing that crossed my mine is that you’re using a CO2 generator. How often and for how long does that run and how many burners does it have on it? I hope we can find a solution for you because it sounds like you’re doing everything else pretty kick ass and I’m sure the flowers look good despite this little mishap so It’d be nice if we can help you cure this.

One more question, does the septoria set in while in veg or does it wait until you put them in flower?

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Are you overhead watering?

Aloha, Unfortunately, using a dehumidifier in the greenhouse is not practical. I would have to fully close it in and further upgrade my ventilation system to make it like a “sun-powered” indoor grow. Right now, it is closed in with greenhouse film from the top about 3/4 of the way down with the bottom open except for the shade cloth outer wall. I use dual 800 cfm exhaust fans mounted at the top of the frame to vent the 1600 cf bloom house plus 2 20" oscillating fans and an 18" high-velocity floor fan. As far as the CO2 generator is concerned, I use a 4-burner propane generator. I added a vented cupola to the roof that the generator hangs in. The bottom of it is about 2 ft. above the plants below. I use a timer system that turns on the generator and turns off the exhaust fans but leaves the oscillating fans going. It is set to repeat the cycle 7 times per day, 4 in the morning before it gets too hot and 3 in the afternoon. In each cycle, the generator is on for 15 minutes, but I leave the exhaust fans off for 30 minutes so the plants have time to absorb the CO2. There is no related temperature or humidity increase that I am aware of. The relative humidity in the greenhouse is the same as ambient humidity at night, which is very high, 80% to 100%. During the day, if it is sunny, the humidity drops well below ambient to between 50% and 65%. Being in a rain-forest, this is the best humidity control I have been able to come up with. Regarding the onset of septoria, I can see it in new clones and begin treating it as soon as the plants are strong enough. It is generally a mild to moderate problem during veg. Where it becomes a real issue is during bloom as that’s when the fungus matures and blooms. From week 3 onward, it works its way up to the top of the plant. My overall flower quality is still good, but the yield goes down by 40% to 50%.

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No, I do not use overhead watering. I mix in a 55-gallon barrel and use a submersible pump, hose and watering wand to water in the soil directly. The only moisture on the leaves is from humidity, pesticide and fungicide spray and I also use an electric fogger to wash the plants every 10 days with an alkalized water mix made with Protekt silica.

Very strange. Get a pack of my genes. I have some very resistant strains andnlets see if it happens again

Can you provide me with a link so I can review your strains, please?

I’m rebuilding it currently. Since I figure nothing going to move till after the new year. I will pm you some of my current stock. It isn’t finished yet

Good afternoon,
I would suggest looking at a better cleaning process as well as possibly a water treatment program.
We at Key Solutions group along with our great partners at Midwest Greenhouse Supply / LL Klink can offer you our surface disinfectant and water treatment product Oxine®WT.
Oxine®WT has been proven time and time again as the “go-to” pathogen control product.
It is OMRI certified organic, EPA approved and registered with the FDA and USDA.
Please follow the link as well as our website
Click on APPLICATIONS and then CANNABIS and you will find all the info on Oxine®WT.

Thank you ,

Tom Johnston, Thank you for your advice. I have downloaded the OxineWT product bulletin and am reviewing it now. I have a rainwater catchment system that goes through a 1 micron sediment filter, a 5 micron carbon filter and a large UVC light treatment to kill microbes. The water that I use for my plants thus has no chemical residue and should be free of microbes. Out of the tap, it has an average TDS of 10 ppm. Would OxineWT be recommended in my case?

Sounds to me like U can set a timer to turn your intake n exhaust off at night n invest in some dehumidifiers to run at night to get that humidity down to 65. Then burn sulfur weekly up to week two of bloom and then spray tru bloom weekly till week 5 bloom. In that environment I’d consider a living soil n let go of the bottle fertilizer.

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It sounds like you definitely know what you’re doing, @ericm. You’ve got all the right answers and have a well thought out grow plan.

Unfortunately fungus spores can stay dormant and viable for weeks at a time, and working in an open environment you’ll have difficulty controlling them. If your neighbors 250 yards away also have the issue it’s unlikely that you’ll be able to avoid it if you’re growing in a partially enclosed greenhouse. The products mentioned earlier are all great ideas and worth trying. The spores can also stay dormant on your mothers and clones and can infect other plants just by rubbing leaves with them. Using something like Regalia from Morrone as a plant dip may give the plants a fighting chance right from the start. After that it’s all about management and cultural practices, minimizing the chance of a healthy plant coming in contact with an unhealthy one, and making sure everywhere the plants go is as clean as possible. Foliar sprays that are slightly acidic or basic can also help in keeping mold spores away - I would have to do some more research to know what would be best for Septoria.

Hopefully you’re able to sort this out! Septoria is such a nasty problem to have to deal with.