Natural high
Member
I think it is more prevalent in cool moist climates. Most of Oz is too hot and dry for it to be a big problem.
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Tales of the great battle of powdery mildew
- Thread starter PaulieWaulie
- Start date
i'm dealing with the same sort of issue. a cold wet snap led to an infection. the environment was corrected but once it established itself, it did not mind the low humidity and on some strains PM took off. i have battled it back with potassim bicarb (greencure), same experience as you. 4-5 days... better if i hit it 3-4.. everywhere said use it til harvest. im paranoid so i switch to h202 half way through flower, which knocks it off for 2 days... way too much work spraying that often... but i have managed to harvest clean buds. had a simmilar outbreak 7 years ago... shut down for the summer and cleaned up well... corrected environmental issues. and was good for 7 years until i was silly and let it happen again.... so.. shut down, clean up.. start again with something resistant... (for me ace's tikal has been pm free throughout this mess)
Lost in a SOG
GrassSnakeGenetics
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
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
Last edited:
Build a proper negative pressure room with a intake filter ,AND Exhaust your air outdoors some how not through out the house spreading spores every where probly breathing it by now .Once plants have it it may hide till proper conditions them boom 4 weeks in everything is covered its systemic don't recycle infected medium and if you use eagle 20 take a few clones off favourite plants treat and put them in clean room destroy all mothers and any old things laying around. i bet its everywhere outdoors around your place in summer thats probly why it keeps coming back. a Lung room with ac is better than OD air cleaner than you can recycle exhaust safely .As been said before start over with seeds drop the chems keep grow area spotless even od clothes can carry spores in to grow space i had it and beat it .I aint no sceintist just a grobro so take it with a grain o salt.
Great post! I hadn't fully considered transpiration's relation to calcium uptake.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
https://www.icmag.com/ic/showthread.php?t=252843
Here is another view on plant resistance through balanced sap ph of 6.4 which relies mainly on balancing calcium and potassium.
insomniac_AU
Active member
Thanks mate that makes sense. It's not something that has ever bothered me fortunately.
Here is another great AEA podcast that discusses mineral nutrition influence on auxin to cytokinin ratios and their role in root to shoot development for allowing balanced nutrient uptake.
https://www.youtube.com/watch?v=dAPhmxCOqqQ
I want to thank you all for your comments. I hope that this conversation will lead to me ridding PM, if not it will also be an entertaining farewell thread of a grower getting done in by mother nature. Maybe people can learn something and have a slightly less frustrating time than me.
Ive got a quick update for you, and after I will respond to a couple specific comments. Thanks again for everyone that is checking in.
NEW GAME PLAN
Ive started harvested 2/6 groups of 8 plants each. I am not replacing them with any new plants. I have turned off one 1000 watt hps light and am down to 2 from 3k. I am only keeping moms in my veg room and am killing all others that I have vegged for this current new run. In 3 weeks the bloom room will be empty. I will sulfur burn every week in veg and bloom room. I will alternate every 3-4 days with a meltatox/ eagle 20 dunk. My goal will be to not have any plants produce any spores for a month, and cure the mother plants. I need do get more information on how long spores live, but from what I have gathered so far it sounds like its just under a month. I can sulfur burn the first month of bloom as well as use other sprays as a preventative. I will clean for a whole day both rooms and the hallway that connects the rooms. As for my soil, I don't think any spores would survive in soil as it is 100% moisture/ fully wet, so they die on contact, as well other bacteria and fungi would destroy them or break them down. My soil will sit in bins, mixed with EWC and amendments and have a whole month to break everything down.
The way my perpetual cycle is set up is I harvest and put 8 new plants into the bloom room every week for 6 consecutive weeks. then 3 weeks break and then cycle repeats. I started harvest 2 weeks ago, so far all have been scrapped, and not trimmed, I will make cannabutter and BHO extracts with it. the 4 groups of 8 plants each that are to be harvested all have pm, and will all receive the same treatment. At least Ive reached a stage where I am ok with just scrapping them and doing extracts etc. I used to trim around it and salvage what I could. Can't be bothered with that anymore, it hurts to much to spent hours and hours on such a sad waste.
A little more info on my Airflow, it is a 10" 232W 1080CFM Vortex S line fan. I have had it turned down to 142W so a 40% reduction. I use a 10" by 40" Mountain Air filter that is under a year old. The ducting is 10" and is 10 Feet long with only two 45 Degree corners. So I figure I have about 500CFM actually moving. The size of the growing area inside the room is 5' by 12' and 8' ceiling.
Vents
The ducting goes through an opening in the closet to the other side which is the bathroom. for the last few months before I started this run I was on, I have the bathroom window open and bathroom door closed, so the air is being pushed out. It does not recirculate throughout the house ever since the spring before this current run (the one that I thought would finally be PM FREE. So I only did that in the winter because I didn't think that in a -30C deepfreeze I had to worry about pests or pathogens (everything is dead frozen outside), venting all that hot air out is very costly and I wanted to be efficient and recirculate this clean(in terms of low C02, more oxygen/ plant filtered The humidity was in the 60% range overall so I thought that it was in the perfect VPD range as well 50% is best for humans too.
Strains
So I was working with 4 strains up until 1 month ago, and over the last month I went all out and germinated all of them. I really had thought that with high temps, low humidity, high airflow, healthy organic soil plants, eagle 20 at flip, and then greencure for spot treatment here and there if I needed to, would be the trick. I was confident that things would work out and I didn't need to shut down.
So here are my current strains. If I kill these I literally wasted all my time and money invested so far, and some of these strains my bodhi cant be bought anymore like the sunshine daydream. I spent a year resarching and buying these strains.
Bodhi
More Cowbell (GSC Forum Cut x 88HP/G13)
Goji OG (Nepali OG x Snow Lotus)
Dream Lotus (Blue Dream x Snow Lotus)
Sunshine Daydream (Bubbashine x Appalachia)
TGA
Agent Orange (Orange Velvet X Jack The Ripper)
Rare Dankness
Scott’s OG (Triangle Kush x Rare Dankness#1)
Karma Genetics
Headbanger (Sour Diesel IBL x Biker Kush 2.0)
Mandarin Kush (Mandarin x Biker Kush)
Tony Greens Tortured Beans
Gorilla Bubble (GG#4 x Sour Bubble)
Lime Gorrilla Bubble (GG#4 x Sour Bubble *Lime Pheno)
Gorilla Haze (SuperSilverSourDiesel Haze x Gorilla Bubble)
DoubleTriple
Strawberry Gum (Strawberry Cough x Pink Bazooka Bubblegum)
Cookies n Gum (GSC Forum Cut x Pink Bazooka Bubblegum)
BadDawg
Brown Sugar Leaf (Brown Sugar x Long Bottom Leaf)
Deadheaded Dragon (Deadhead x 3 Headed Dragon)
Atonic Dragon (Atonic x 3 Headed Dragon)
Female Seeds
Blueberry Cheesecake (Blueberry x Cheese)
the PM i get isn't on fan leaves noticebily visible. I have been thinking I am PM free for all of the last 9 weeks, and on the day of harvest as you open them up you see its all inside the buds even the top top cola. So no matter the airflow or low humidity or max light, inside the buds all that changes. - low light, no direct air movement , high humdity. And sprays cant get to these areas either, so spraying is pointless, esp for many you stop halfway through bloom, and thats when pm usually just gets into gear
As you can see I really Lollipopped pretty hard.
My fan/ filter, placed high up
my thermostat showing high low records. I can take a pic everyday for anyone that doesn't belive my reported RH temps or ability to keep them in check!
Ive got a quick update for you, and after I will respond to a couple specific comments. Thanks again for everyone that is checking in.
NEW GAME PLAN
Ive started harvested 2/6 groups of 8 plants each. I am not replacing them with any new plants. I have turned off one 1000 watt hps light and am down to 2 from 3k. I am only keeping moms in my veg room and am killing all others that I have vegged for this current new run. In 3 weeks the bloom room will be empty. I will sulfur burn every week in veg and bloom room. I will alternate every 3-4 days with a meltatox/ eagle 20 dunk. My goal will be to not have any plants produce any spores for a month, and cure the mother plants. I need do get more information on how long spores live, but from what I have gathered so far it sounds like its just under a month. I can sulfur burn the first month of bloom as well as use other sprays as a preventative. I will clean for a whole day both rooms and the hallway that connects the rooms. As for my soil, I don't think any spores would survive in soil as it is 100% moisture/ fully wet, so they die on contact, as well other bacteria and fungi would destroy them or break them down. My soil will sit in bins, mixed with EWC and amendments and have a whole month to break everything down.
The way my perpetual cycle is set up is I harvest and put 8 new plants into the bloom room every week for 6 consecutive weeks. then 3 weeks break and then cycle repeats. I started harvest 2 weeks ago, so far all have been scrapped, and not trimmed, I will make cannabutter and BHO extracts with it. the 4 groups of 8 plants each that are to be harvested all have pm, and will all receive the same treatment. At least Ive reached a stage where I am ok with just scrapping them and doing extracts etc. I used to trim around it and salvage what I could. Can't be bothered with that anymore, it hurts to much to spent hours and hours on such a sad waste.
A little more info on my Airflow, it is a 10" 232W 1080CFM Vortex S line fan. I have had it turned down to 142W so a 40% reduction. I use a 10" by 40" Mountain Air filter that is under a year old. The ducting is 10" and is 10 Feet long with only two 45 Degree corners. So I figure I have about 500CFM actually moving. The size of the growing area inside the room is 5' by 12' and 8' ceiling.
Vents
The ducting goes through an opening in the closet to the other side which is the bathroom. for the last few months before I started this run I was on, I have the bathroom window open and bathroom door closed, so the air is being pushed out. It does not recirculate throughout the house ever since the spring before this current run (the one that I thought would finally be PM FREE. So I only did that in the winter because I didn't think that in a -30C deepfreeze I had to worry about pests or pathogens (everything is dead frozen outside), venting all that hot air out is very costly and I wanted to be efficient and recirculate this clean(in terms of low C02, more oxygen/ plant filtered The humidity was in the 60% range overall so I thought that it was in the perfect VPD range as well 50% is best for humans too.
Strains
So I was working with 4 strains up until 1 month ago, and over the last month I went all out and germinated all of them. I really had thought that with high temps, low humidity, high airflow, healthy organic soil plants, eagle 20 at flip, and then greencure for spot treatment here and there if I needed to, would be the trick. I was confident that things would work out and I didn't need to shut down.
So here are my current strains. If I kill these I literally wasted all my time and money invested so far, and some of these strains my bodhi cant be bought anymore like the sunshine daydream. I spent a year resarching and buying these strains.
Bodhi
More Cowbell (GSC Forum Cut x 88HP/G13)
Goji OG (Nepali OG x Snow Lotus)
Dream Lotus (Blue Dream x Snow Lotus)
Sunshine Daydream (Bubbashine x Appalachia)
TGA
Agent Orange (Orange Velvet X Jack The Ripper)
Rare Dankness
Scott’s OG (Triangle Kush x Rare Dankness#1)
Karma Genetics
Headbanger (Sour Diesel IBL x Biker Kush 2.0)
Mandarin Kush (Mandarin x Biker Kush)
Tony Greens Tortured Beans
Gorilla Bubble (GG#4 x Sour Bubble)
Lime Gorrilla Bubble (GG#4 x Sour Bubble *Lime Pheno)
Gorilla Haze (SuperSilverSourDiesel Haze x Gorilla Bubble)
DoubleTriple
Strawberry Gum (Strawberry Cough x Pink Bazooka Bubblegum)
Cookies n Gum (GSC Forum Cut x Pink Bazooka Bubblegum)
BadDawg
Brown Sugar Leaf (Brown Sugar x Long Bottom Leaf)
Deadheaded Dragon (Deadhead x 3 Headed Dragon)
Atonic Dragon (Atonic x 3 Headed Dragon)
Female Seeds
Blueberry Cheesecake (Blueberry x Cheese)
the PM i get isn't on fan leaves noticebily visible. I have been thinking I am PM free for all of the last 9 weeks, and on the day of harvest as you open them up you see its all inside the buds even the top top cola. So no matter the airflow or low humidity or max light, inside the buds all that changes. - low light, no direct air movement , high humdity. And sprays cant get to these areas either, so spraying is pointless, esp for many you stop halfway through bloom, and thats when pm usually just gets into gear
As you can see I really Lollipopped pretty hard.
My fan/ filter, placed high up
my thermostat showing high low records. I can take a pic everyday for anyone that doesn't belive my reported RH temps or ability to keep them in check!
'Boogieman'
Well-known member
My well water is a high ph 8+ I have always used this plus green cure. I only have had it show up on the bottom leaves, i spray then remove the leaf but I never had it in buds yet.
Thanks all for the support. It makes this whole thing better even just talking with people about it.
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 appreciate your knowledge on this, it actually sounds like you know what your talking about, and it seems to be in line with my experience. I think what is so difficult about pm, is that there two stages of life, both with different optimum ranges for temp and rh. There is the germination stage, and then once established there is sporulation of that established fungi sytem. So when it has already germinated in high humdity and you lower it, that almost signals it to sporulate. Combined with the VPD stress if its really hot as well I think thats what really set it off, as temps are in the 80s and humidity 30-40%. Altough I would say I don't think they suffered dehydratin as I still needed to water all plants every 1-3 days. I notice when the temperature is 5F lower even I can go 3-4 days between water
Yeah I have read that article,
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.
glad to see im not the only one, well have to stay in touch as you go through your process. I think thats why a purpose built room that you can 100% clean and start a new is the way to go. And not doing perpetual cycles as well, as you can clean between runs. So whats going to be your exact shutting down, cleaning, starting over process going to be this time? what was it last time?
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.
I appreciate your knowledge on this, it actually sounds like you know what your talking about, and it seems to be in line with my experience. I think what is so difficult about pm, is that there two stages of life, both with different optimum ranges for temp and rh. There is the germination stage, and then once established there is sporulation of that established fungi sytem. So when it has already germinated in high humdity and you lower it, that almost signals it to sporulate. Combined with the VPD stress if its really hot as well I think thats what really set it off, as temps are in the 80s and humidity 30-40%. Altough I would say I don't think they suffered dehydratin as I still needed to water all plants every 1-3 days. I notice when the temperature is 5F lower even I can go 3-4 days between water
Glad to hear you beat it, I think I will make a thread in the future for people to simply share there experiences and steps they took and outcome. Theres not enough documented about the actual success that people had. I know you gave a rough outline of what I should do, but can you also share what steps you took yourself last time? Thanks!Build a proper negative pressure room with a intake filter ,AND Exhaust your air outdoors some how not through out the house spreading spores every where probly breathing it by now .Once plants have it it may hide till proper conditions them boom 4 weeks in everything is covered its systemic don't recycle infected medium and if you use eagle 20 take a few clones off favourite plants treat and put them in clean room destroy all mothers and any old things laying around. i bet its everywhere outdoors around your place in summer thats probly why it keeps coming back. a Lung room with ac is better than OD air cleaner than you can recycle exhaust safely .As been said before start over with seeds drop the chems keep grow area spotless even od clothes can carry spores in to grow space i had it and beat it .I aint no sceintist just a grobro so take it with a grain o salt.
I wonder if I can juice a bunch of plants and measure the ph of that juice? I don't want to spend hundreds of $$$ at a time when Im on my wits end and might shut her down for good.
No, but I will sulfur burn as part of my strategy to clean my rooms soon enough. Again, if I stop in week 4, then a week a week later I would have spores landed/germinated/sporulating.
My tap PH is 7.8, I use 10ml per gallon, at that rate it doesn't burn pistils. I had pretty good success with it before, I would dunk plants into a bucket of it once per week. And then I would dunk in plain water day before harvest to remove any buildup from doing this during all of flowering. But with my poor health, and 48 plants in the bloom room I can not spray every week and I think it does affect the apearance,smell,quality, so I fixed my environment and tried to grow healthy plants and basically didn't use greencure just to see how it would make out on its own, well I got the answer LOL.
Check out or google UC Davis IPM for powdery mildew. It’s about grapes but is pretty comprehensive in explaining life cycle of pm. More than than I can type into a phone.
It has a risk index to identify times for outbreak, based on temps and humidity for x number of hours. Best explanation I’ve run across yet.
70-85 degrees is optimal for pm reproduction, 95 and 65 degrees inhibits growth.
It has a risk index to identify times for outbreak, based on temps and humidity for x number of hours. Best explanation I’ve run across yet.
70-85 degrees is optimal for pm reproduction, 95 and 65 degrees inhibits growth.
Sweet Il check it out, Im a PM info spunge, maybe when this is done Il become a pm specialist and go around the country cleaning up grows.
PM basically adapted perfectly to the indoor cannabis growing environment 70-85F, 50-70RH !
the quality is not the greatest since icmag lowers it. But there is some on every bud somewhere, I know that it won't kill anyone, but I don't want someone to smoke this and find some pm and say this has mold on it. I pride myself as a grower to not accept that. Also the vigor is reduced, I find that plants with pm often aren't very healthy. I don't have it under control LOL
I hear ya, just saying to think twice before scrapping so many great genetics when you are this close to beating it! Edit: I forgot you mentioned a disability, in which case it would be understandable to call it quits.
BTW, the decreased plant vigor is the underlying issue which allows PM to sporulate. I suspect your soil mix isn't draining well enough. 50% perlite should be plenty, but you also need to account for particle size of your medium.
BTW, the decreased plant vigor is the underlying issue which allows PM to sporulate. I suspect your soil mix isn't draining well enough. 50% perlite should be plenty, but you also need to account for particle size of your medium.
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Green Squall
Well-known member
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
https://www.amazon.com/Zero-Toleran...968798&sr=8-1&keywords=ed+rosenthal+fungicide
