Tales of the great battle of powdery mildew

Whammy Bar · Jun 26, 2018

I am currently having experiences quite similar to yours. I have a 4000w room, 12 Stardawgs in 10 gallons of coco each. I also have grown in my backyard for the last 3 years. I always had a little PM outdoors by the end of flower. Last summer I didn't give neem oil foliars every 5 days up to flower like normal and I had a full outbreak, and ended up dfragging it inside to my indoor garden. I shut down this winter for 2 weeks, cleaned everything, and started up again(with plants that were systemically still infected) and got through a harvest with no PM. I kept all plants as thinned out as possible and made sure airflow was as perfect as possible. Next run it came back with a vengeance. I tried spraying the plants down with ozonated water every few days...that would wash the PM off of fan leaves, but once it reaches anything sticky it isn't going anywhere.
I harvested those plants about 7 weeks ago...I ran an ozone generator in the room overnight, then cleaned the room as well as I could and threw my 12 Stardawg plants in to flower. My room is about 12'x12', it has 3 wall mounted fans blowing over the canopy and an oscillating fan on the ground blowing underneath them. The room is sealed and supplemented with co2. I have a minisplit and a quest dehumidifier...temp is 80 lights on, 74 lights off, always between 49-53 percent RH. I used neem foliars until about flower day 10 and add silica to every watering. Today is day 45 of flower and I just found 2 little dots of PM. I will kill everything this time if I have another full outbreak.

Thanks for sharing your story with us. I just sat down to read all the PM info I could find on Icmag for the 12th time and was surprised to find that someone is going through the exact same thing. I hate the thought of losing the handfull of straind that I consider keepers, but I cant keep living like this LOL. Best of luck to you my friend.

Whammy Bar · Jun 26, 2018

Green Squall said:
Has anyone used this product? I like that it's plant based and you can use it up until a week before harvest. I've never had PM indoors (knock on wood), but always get it on my outdoor plants.

https://www.amazon.com/Zero-Toleran...968798&sr=8-1&keywords=ed+rosenthal+fungicide

About 7 years ago I had a friend that sprayed his crop with this stuff at the recommended doses up until a few days before harvest...the dried product smelled and tasted like potpourri. It was completely ruined.

PaulieWaulie · Jun 26, 2018

Whammy Bar said:
I am currently having experiences quite similar to yours. I have a 4000w room, 12 Stardawgs in 10 gallons of coco each. I also have grown in my backyard for the last 3 years. I always had a little PM outdoors by the end of flower. Last summer I didn't give neem oil foliars every 5 days up to flower like normal and I had a full outbreak, and ended up dfragging it inside to my indoor garden. I shut down this winter for 2 weeks, cleaned everything, and started up again(with plants that were systemically still infected) and got through a harvest with no PM. I kept all plants as thinned out as possible and made sure airflow was as perfect as possible. Next run it came back with a vengeance. I tried spraying the plants down with ozonated water every few days...that would wash the PM off of fan leaves, but once it reaches anything sticky it isn't going anywhere.
I harvested those plants about 7 weeks ago...I ran an ozone generator in the room overnight, then cleaned the room as well as I could and threw my 12 Stardawg plants in to flower. My room is about 12'x12', it has 3 wall mounted fans blowing over the canopy and an oscillating fan on the ground blowing underneath them. The room is sealed and supplemented with co2. I have a minisplit and a quest dehumidifier...temp is 80 lights on, 74 lights off, always between 49-53 percent RH. I used neem foliars until about flower day 10 and add silica to every watering. Today is day 45 of flower and I just found 2 little dots of PM. I will kill everything this time if I have another full outbreak.

Thanks for sharing your story with us. I just sat down to read all the PM info I could find on Icmag for the 12th time and was surprised to find that someone is going through the exact same thing. I hate the thought of losing the handfull of straind that I consider keepers, but I cant keep living like this LOL. Best of luck to you my friend.

You have a sealed room which gives you more than me an opportunity to dial it into that range where "common knowledge" says pm spores can't germinate/sporualte. Which is 30-40% RH. I pull exterior air in 24/7 directly in the room, and I am lucky that it is usually 30-50% RH, but if it rains it jumps to 70% RH for even just one lights off cycle, and from what I have read that is all it takes (2 hours for spore germination).Im thinking that's what kickstarted this last spore cycle, plus my refusal to spray greencure and let the environment control the pm.

I wonder why your first run after shutting down for 2 weeks had no pm, and then the next cycle it went beserk?

So I would say out of curiosity sake have RH at 30-40% and see what happens. Test the common knowledge once and for all.

Since you have just 1 genetics it is not a major loss if you had to kill them and start over. This epxerience has also shown me the value of having a purpose built room, not necessarily sealed but flush walls, no nooks and crannies, something you can completely fumigate/clean/wipe down/ in between runs and start fresh. I have 2 bedrooms im growing in on my main floor with exhaust running through part of the house before it goes out, so the task of cleaning succesfully is daunting.

You could try eagle20 to cure the moms, then take clones, veg for a month, and then put in bloom. There is a thread on eagle 20 thats 140 pages, that I also need to revisit myself to see if people really did cure their moms. I made it maybe 3-40 pages in and all it was people asking over and over again the simple instructions. But few people came back with details of their situation and the final outcome.

PaulieWaulie · Jun 26, 2018

UPDATE

I have started killing off plants that I had pre vegged and ready to go into bloom. Of course, this current veg cycle is one of the best yet, with all the strains I have been dying to grow for over a year now. The leaves are all praying, with my organic soil and teas every week. Lush vigorous growth with soft tender tips everywhere and leaves just unfolding as they grown - this is what Ive always wanted, and now that I have it I need to kill extras and put everything on hold and break my prepetual cycle! I even had 3 Gorilla Bubbles BX2 that were 3 days in bloom, and I actually pulled them back out and into veg when I decided I needed to shut down for a month. So I am killing all mutliples and only keeping 1 plant of each pheno. Once my current seedlings sex I figure with a 50% female/male ratio I will end up with 64 total plants. An average of 3 phenos of each of my 20 strains. after the 1 month shut down, I will take clones of each plant and then put it into flower.

Even If my worst nightmare happens and PM comes back after the shut down, I am thinking with these 64 phenos I will find a couple that are resistant to the pm. Then I will simple grow those out for the next 6 months.

I have learned a lot from this, and can appreciate the value of a purpose built room with dedicated direct intakes and exhaust, that can be easily shut down and cleaned between cycles, so if you do get some pest, which will happen sooner or later, I can just shut down and start over. Another lesson is to focus on maybe 2-3 strains, so if you need to kill everything its not that bad.

These genetics cost me $900 CAD, but I have 10 strains left with an average of 5 seeds each. so when I start up in a few years again, I do have something left to get a few good females.

It is a harsh lesson, for such a new grower that has never had much success and hit his stride, but you learn the most from these I suppose. After dealing with PM, no other pest/pathogen will scare me.

jackspratt61 · Jun 26, 2018

PM

PM

Try Regalia from Marrone Industries...just approved for cannabis. It works.

Somatek · Jul 1, 2018

I'm a big fan of potassium bicarbonate for PM control, relatively cheap & added to neem oil makes an effective weekly fungicide/pesticide.

Guy Brush · Jul 1, 2018

PaulieWaulie said:
Yes I let the pot dry out almost compeltey until the top 1 inch is bone dry. then I give it a good soak to run off. I never foliar feed, or get water on the plants, or water before liights off. I water first thing on lights on everyday. I have a garden outside, I grow zuchinnis as well. Its difficult to say if the pm strain on them likes cannabis as well and is not species specific like most. Also spores travel in wind and could fly for miles and miles so really it could come from anywhere. Im pretty sure that the main source of spores after inital outbreak has been from my own pm plants and spores in the rooms.

I'd say skip the zucchinis if they got it.

growingcrazy · Jul 16, 2018

Regalia does work and is OMRI. Water it in and foliar.

My first thought after reading through here... What is on the other side of the panda film? If you have the ability to get everything out of that room but lights, fans and a dehumidifier, that is what you need to do. Bare walls and white paint, no bare wood 2x's in the room...anything that isn't a clean slick surface that can be wiped down. If your carbon filter was in the room with PM, it has to go too.

Most everything else can/should be sanitized, including your intake ducting from the house to the room. I also heat my house from oct-april with exhaust and have zero problems. You have the fan CFM to use high quality furnace filters on the intake too.

Take care.

WizardofWind · Jul 25, 2018

I was at a cannabis expo and Wizards-Wand had a booth and were selling a wand that had 2 6" UV-C bulbs about 3" apart. You put the branch between the bulbs and run the wand along the branch. The top bulb gets everything on top of the branch and the bottom bulb does the same on the underneath of the branch. I knew UV-C was germicidal and it made sense so I got one and not only does it kill mold, mildew, bacteria and viruses (it's germicidal) but it kill soft bodied bugs like spider mites, thrips, mealy bugs etc. It was amazing. Best of all, the plant produces resin to protect itself from the sun's UV rays and by passing the wand over the branch the plant gets a signal to produce excess resin and higher THC. Loaned it to a friend and he wiped out the worst infestation of spider mites I'd seen in two applications. it gets into their DNA and they can't function.
Works great for me.

Kushron · Dec 22, 2018

Wow best most useful statement

Wow best most useful statement

Lost in a SOG said:
Okay a bit of basic botany here for your consideration and to add some perspective.

Calcium, an immobile nutrient, requires consistent transpiration to keep it being pulled up the plant at the desired rate, depending on the rate of new growth.

With prolonged exposure, plants will actually close their stomata in response to very high VPD or Vapour Pressure Deficit, which is relatively low humidity and high temperature, they have to protect themselves from being drunk alive after all.

PM actually most often follows high VPD stress because plants have to maintain the correct % of water in them relative to the outside world otherwise they become turgid (too full of water) or flaccid (lacking water).

So very low RH and a bit of heat > makes them close their stomata > Calcium deficiency kicks in as transpiration stops > (as mentioned before by rjrom90) then the plants natural physical defence against PM colonising and fruiting is somewhat retarded in this lack of Calcium, and probably a few other immobile and mobile nutrients as well.

PM is usually patchy and this is often because negative stomatal conductance (closing) in response to very high VPD is also distributed in a patchy manner throughout the plant, often leaves nearest to air currents suffer worse due to the extra drying effect of the air movement but it is often the same with the signs of Ca deficiency as well, patchy. when then mother nature, or a guy with a watering can, forces a slight raise in RH (or sudden change in internal and external pressures the other way) boom the PM fruits which is what you see on the leaves, the spores might have been sat there for weeks just waiting to bloom themselves, but it wasn't any rise in RH causing a sudden explosion it was the stress that came before that that helped so many spores colonise your plants.

When you lower the Humidity to fight PM you are actually helping it by not paying attention to a healthy VPD as outlined in VPD charts, especially growing under a 1000w which gives off so much IR and far IR that the humidity around your leaves could be getting down to extreme dryness and the temps well above 30C.

Part of the reason that sometimes you don't detect that your plant is experiencing heat/water stress is that various Cannabis genetics make use of the C3 and C4 sugar pathways slightly differently when photosynthesising in different conditions hence she/they may be experiencing very high stress and low calcium levels but the genetics aren't so hungry for the calcium except that they all still need it as a protective measure to some extent.

IMO It's cause correlation confusion that people think that high RH causes PM or that lowering RH will help, which only stresses the plants more and as so so many have noticed actually can help the PM colonise further and faster more plants as you stress them all out to try and save the more sensitive or exposed genetics that were afflicted first.. What will help is if you respect the fact that the ideal transpiration rate for stress free growth is what you see on a VPD chart for a specific temperature and RH. Paranoia and over complication is a big problem for us persecuted growers. imo provide the plant with a stress free environment and you won't have to spray them with pointless retroactive shite.

I think possibly it is the genetics thing that makes it harder for people to see clearly what is going on with this form of stress, with indicas and sativas responding differently to VPD changes and now we have such a mish mash of naively selected slightly sensitive polyhybrids muddying the waters.

But in short by water stressing them with high heat and low RH you are leaving the door wide open for the PM. Once it's there it's there.

https://www.bing.com/th?id=OIP.zDJW-ObCisUUaaRxn0YK7QHaHA&pid=Api

Thank you so much for this valuable information this really puts things into perspective

SuperBadGrower · Jan 10, 2019

Very informative thread! And hey at least you guys are allowed to get in the ring and fight. Here in Europe it's impossible to get any products that actually work. Eagle 20, Greencure, Hydroguard, anything, just name it and you can't get it. My method against PM is to pray to Brussels and dunk my plants in H2O2 after I am forced to harvest early. :biglaugh:

chronic82 · Jan 15, 2019

One dose of actinovate at 2 ounces per quart during veg and you’ll never see it again

Dankwolf · Jan 15, 2019

SuperBadGrower said:
Very informative thread! And hey at least you guys are allowed to get in the ring and fight. Here in Europe it's impossible to get any products that actually work. Eagle 20, Greencure, Hydroguard, anything, just name it and you can't get it. My method against PM is to pray to Brussels and dunk my plants in H2O2 after I am forced to harvest early.

I had pm bad once (hole garden ) and fully got rid of it in 3-6 month with a schedule of 1% milk, neem and h202 foiler sprays . hard part is getting it out of mother plants . they say its systemic but between spray schedule and nagitive pressure in grow room . I have had not seen a single spot or out break in 2 years.

If there is enough interest I will find my post / thread that has the schedule . let me know ? :tiphat:

It is possible to rid the pm with out chemicals .

chronic82 · Jan 15, 2019

Y’all are going at this wrong. Research actinovate. It’s active ingredient is an old antibiotic that humans used to take before amoxicillin came out. It will live in the surface of the leaf and eat any bacteria that lands on it. I’ve never seen it not work. Use double recommended dose with some coco wet. Spray weekly or just once

ion · Mar 15, 2019

2 plants in veg, both clones from plants that had PM, not heavily. one is johnny blazeXc99 the other is satori.

ive been on the PM path for 4month, i understand most say to kill these plants but aint gonna.

plant health is good and on the up, environment is not optimal but being addressed and is priority uno.

16lb of literature to digest pronto.

my question is, if i take cuts from these girls and dip them in.....? h202, milk, Gcure, isopropyl, etc. fully dipped, let them scuba for a minute or so do you think they're free from PM right then and there?

p0opstlnksal0t · Mar 15, 2019

I keep hearing it posted multiple times on grow boards that pm is systemic. Can someone please link some studies or biology reports showing that the pm that everyone is dealing with on these boards is systemic and different than all other species of pm that grows on all other fruiting and flowering plants that is NOT SYSTEMIC.

I wood · Mar 15, 2019

Pm is not systemic, it is opportunistic, tenacious, and the spores are omnipresent.
This makes it appear systemic to ignorant people who don’t educate themselves enough to understand the difference.

xxPeacePipexx · Mar 15, 2019

Current research has not revealed any of the Powdery Mildew strains that attack Cannabis as being systemic. How could those decades old cuts circulating harbor this disease? They would have been disposed of eventually regardless of how much poison was applied. Imho Cannabis is a host, nothing more, nothing less. But like the protozoan parasites, it's a nightmare once the plant becomes the host and environment and health either welcomes the fungus, or it's denied access at the door, so to say.

When I read about others fighting PM for months on end, I have no other thoughts about this other than it being environments that are the bane, verses it being strain or type (Indica) related. Ask any avid gardener about PM and the subtle signs and conditions that trigger the spores to grow and you will have a better understanding of how this disease is prolific only if the environmental conditions are ideal..

I know that you will find more people using synthetic and other harsh methods to control the different strains of PM that attack Cannabis, but it is not really necessary unless you just want to put bandages on the wound while never fixing the environment. In the natural world, the only thing needed to snuff out fungus and pests is horticultural oils derived from plants. I have been on both sides of the fight more than once and I don't like to spray anything unnatural on my plants, let alone in my own home..

ion · Mar 15, 2019

not systemic. as peacepipe says, how could it be?...opportunistic is succinct and clear. understanding/knowledge of life cycle of PM + healthy plants + ideal enviro = PMless.

i see it and understand the broad strokes but am not there yet. i had it semi-bad on just about everyone in house, 6-10 strains, sog. chopped like a sushi chef and gave lots of attention to the survivors, now its new seed germ time.

and the war is still on as my environment is damn-near impossible to get out of the PMorgy temps/humiture range. moisture stays level around 45 as spring approaches and the outside is rising bigly. temps fluctuate tween 65 and 72 roughly. the enviro is the problem and its next on the list to addfress, but ive got to stop the bloodflow first to fix the wound. the pm i'm seeing today is very spotty, leaf only, spots are smaller than a standard watch battery and there's not a lot......the plants want to win i just have to stop obstructing them with my friggin enviro

as for my ^question^ with my enviro getting more dialed in over the next couple weeks would a serious h202 bath of clones from a slightly infected plant free it of the pm?

ion · Mar 15, 2019

secondary programmable heat source and dehumidifier will get the room optimal i think. its a blown-air furnace and the room is farthest in duct from it, corner of house that gets slammed with wind.

Tales of the great battle of powdery mildew

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