My first dealing with the infamous white powdery mildew

[The Brown Cow]

Hello every one I'm the Brown Cow and I have been growing for 2 years now lol a little AA humor but ironically my first grow went rather well , I didn't get spider mites, I didn't get white powdery mildew and this was in a 4x4 tent with King LED lights purchased on Amazon . I only yielded like 4 ounces out of 6 plants under 1500 watt equivalent light but it went good . I grew in fox farms soil and used the trio pack and it worked , at the begging of this year I got two tents going and I had my first encounter with spider mites and used mitey wash and had to keep using it for almost the entire grow 12 plants but I got through it and yielded 10 ounces all together using 2 1500 watt King LED lights with some super cropping done . So I upgraded again and now have built a dedicated grow shed with a 4x8 flower room with a 6 inch inline fan bringing constant fresh air in and a 6 inch inline fan with a carbon filter blowing air out , 4 fans to circulate air in the room . I use a variety of nutrients now like big grow, big bloom , tiger bloom, pk booster, Koolbloom , monster bloom and am about to start adding overdrive. I dont use all the nutes together just so you guys have an idea of what I have used and Im growing in soil ,watering from a reservoir using drip lines and 3 600 watt hps light . So I have been upgrading each grow and to me I feel like it was all going good and I'm half way through the flowering stage when I notice some leaves with some white spots . I know from reading threads and watching youtube that its white powdery mildew and I have tried the milk solution , I have tried the peroxide solution and it didnt work so I bought some greencure hopefully it helps but I have two questions if anyone can answer please, question one all my Granddaddy purples have the white powdery mildew and the only two Girl scout cookies I have in the room right next the Granddaddy purples touching each other do not have the mildew on the plants why is that . question two I live in the high desert in California and I have a hard time getting my humidity levels up currently they are 25 percent and have never gone over 30 percent how did I get white powdery mildew the air is super dry up here . Any ways I hope it wasnt too much for my first post and any answer or even criticism will be greatly appreciated . Brown Cow out !

 

[Gond00s]

Well few problems not enough airflow in the tent in a 4x8 I have two 18 inch box fans shooting to the middle and that's just enough and whats is your rh at lights out mine loves to spike at lights out when the temp goes down and that spike will really destroy yields I have grown a gdp from seedsman super dense and I mean dense. at the point I had to just cull the whole room and bleached ozoned wiped everything down in the room once I see pm I can almost say you should just cull them that's imo

 

[The Brown Cow]

Well few problems not enough airflow in the tent in a 4x8 I have two 18 inch box fans shooting to the middle and that's just enough and whats is your rh at lights out mine loves to spike at lights out when the temp goes down and that spike will really destroy yields I have grown a gdp from seedsman super dense and I mean dense. at the point I had to just cull the whole room and bleached ozoned wiped everything down in the room once I see pm I can almost say you should just cull them that's imo

For air flow I believe Im good its like 300 cfms bringing air in and i have 4 full size oscillating fans but i will give it a recheck. As for my rh when the lights go out Im at 28/29 percent . like I said its very very dry up here . my only guess is my buddy had an extra granddaddy purple clone that i took from him and he has super high rh like in the 80's maybe his clone the the trojan horse. Any ways what about the girl scout cookies not getting the white powdery mildew any pointers on that .

 

[Gond00s]

For air flow I believe Im good its like 300 cfms bringing air in and i have 4 full size oscillating fans but i will give it a recheck. As for my rh when the lights go out Im at 28/29 percent . like I said its very very dry up here . my only guess is my buddy had an extra granddaddy purple clone that i took from him and he has super high rh like in the 80's maybe his clone the the trojan horse. Any ways what about the girl scout cookies not getting the white powdery mildew any pointers on that .

im not really sure but if your in flower and got pm I would toss if the gsc has nothing just keep a very close eye on her it depends on how bad the pm is

 

[Renfro]

PM likes to have hot dry days and cool moist nights. When air cools the RH% rises. Does your temperature drop when the lights are out? Do you monitor the RH% when the lights are off?

The most common cause of PM is allowing the lights off temps to drop.

Defoliation helps a little with the transpiration and air circulation (to prevent areas of higher humidity). Lollipopping the bottoms helps.

You want to keep the RH% between 40 and 50% all the time. So you need to raise it when the lights are on and probably drop it when the lights are off.

Growing strains that are mold and mildew resistant is always an option but very limiting.

The large paragraph lost me but are you in flower? If not then you can use Eagle 20.

Actinovate and serenade are products that can be used in flower.

The green cure basically tried raising the pH of the plants surfaces. PM likes an acidic environment. Make sure any and all foliar applications alkaline in pH. Using potassium bicarbonate, like all non systemics, requires 100% coverage and thats difficult.

 

[westcoast420]

Hard to believe at that low of rh you'd have pm, post some pics.

 

[Gond00s]

Night time temps it’s the same temp during the day and at 30-35rh during the day I think I got a good control on pm now

 

[The Brown Cow]

Ok these pictures are right now at 9:08 in the morning my lights have been off for two hours . I run lights from 7pm to 7 am . I have a total of 80 gallons of water in that room and my humidity is only at 42

 

[The Brown Cow]

Sorry I forgot a had a couple of other strains in there but still the GSC don’t have the pm

 

[An1m0ssity]

PM likes to have hot dry days and cool moist nights. When air cools the RH% rises. Does your temperature drop when the lights are out? Do you monitor the RH% when the lights are off?

The most common cause of PM is allowing the lights off temps to drop.

Defoliation helps a little with the transpiration and air circulation (to prevent areas of higher humidity). Lollipopping the bottoms helps.

You want to keep the RH% between 40 and 50% all the time. So you need to raise it when the lights are on and probably drop it when the lights are off.

Growing strains that are mold and mildew resistant is always an option but very limiting.

The large paragraph lost me but are you in flower? If not then you can use Eagle 20.

Actinovate and serenade are products that can be used in flower.

The green cure basically tried raising the pH of the plants surfaces. PM likes an acidic environment. Make sure any and all foliar applications alkaline in pH. Using potassium bicarbonate, like all non systemics, requires 100% coverage and thats difficult.

So, just so I get a better understanding of this as I'm in early flower atm... if the humidity drops that's fine, as long as I maintain lights on temp? Less chance of pm to grow? Also obviously having good airflow. What if I use an ionizer during lights out? Would that help keep that shit away?

 

[Renfro]

So, just so I get a better understanding of this as I'm in early flower atm... if the humidity drops that's fine, as long as I maintain lights on temp? Less chance of pm to grow? Also obviously having good airflow. What if I use an ionizer during lights out? Would that help keep that shit away?

If the humidity gets below 40%, 35% for sure then the powdery mildew spores propagate easily so we want to avoid the RH% getting too low as well as too high. PM really thrives when it has the cool humid times and the warm dry times. So regardless of lights on or off we want to keep the rh% between 40 and 50 percent, ideally 40 and 45% but it's nearly impossible for most to keep the window that precise so I say 40 - 50% being realistic. Maybe 38 to 48 is more ideal. Accurate hygrometers that respond quickly are very much required.

Now, when lights go off the humidity generally spikes and we want to avoid this pushing us outside the target range. So when the lights are about to go off it would be ideal if we are on the low side of the RH% range (40% and not 50%). This gives us a little head room to fight that initial RH spike.

Here is a graph showing one of my flowering rooms when the lights go off at 3:45 AM in this case.



You can see the temps drop and the RH% spike. In my rooms the dehumidification creates heat and when the room hits 80 my intake (cold dry air) runs it down to 75F to push some humidity out but not get it so cool that the dehumidifiers don't work. As you can see it's a balancing act. When my plants are at peak drink the dehumidifiers require some help from my ventilation, good thing I live in a fucking desert with low RH% lol.

I hope that helps make sense of the situation.

 

[An1m0ssity]

If the humidity gets below 40%, 35% for sure then the powdery mildew spores propagate easily so we want to avoid the RH% getting too low as well as too high. PM really thrives when it has the cool humid times and the warm dry times. So regardless of lights on or off we want to keep the rh% between 40 and 50 percent, ideally 40 and 45% but it's nearly impossible for most to keep the window that precise so I say 40 - 50% being realistic. Maybe 38 to 48 is more ideal. Accurate hygrometers that respond quickly are very much required.

Now, when lights go off the humidity generally spikes and we want to avoid this pushing us outside the target range. So when the lights are about to go off it would be ideal if we are on the low side of the RH% range (40% and not 50%). This gives us a little head room to fight that initial RH spike.

Here is a graph showing one of my flowering rooms when the lights go off at 3:45 AM in this case.

View attachment 4431167

You can see the temps drop and the RH% spike. In my rooms the dehumidification creates heat and when the room hits 80 my intake (cold dry air) runs it down to 75F to push some humidity out but not get it so cool that the dehumidifiers don't work. As you can see it's a balancing act. When my plants are at peak drink the dehumidifiers require some help from my ventilation, good thing I live in a fucking desert with low RH% lol.

I hope that helps make sense of the situation.

Absolutely man, I appreciate it.

 

[The Brown Cow]

Hard to believe at that low of rh you'd have pm, post some pics.

posted them

 

[Powertech]

My key to keep PM away is massive amounts of air flow, not directly on the plant though like a fan. I’m in a slightly smaller than 5’x5’x7’, and have 450scfm intake and 450scfm exhaust. Just 3 6” fans in the tent. Keeps plants breathing nicely too

That’s 175 cubic feet of space with 450ish cubic feet of air being exchanged every minute

 

[Bourbon 2]

If the humidity gets below 40%, 35% for sure then the powdery mildew spores propagate easily so we want to avoid the RH% getting too low as well as too high. PM really thrives when it has the cool humid times and the warm dry times. So regardless of lights on or off we want to keep the rh% between 40 and 50 percent, ideally 40 and 45% but it's nearly impossible for most to keep the window that precise so I say 40 - 50% being realistic. Maybe 38 to 48 is more ideal. Accurate hygrometers that respond quickly are very much required.

Now, when lights go off the humidity generally spikes and we want to avoid this pushing us outside the target range. So when the lights are about to go off it would be ideal if we are on the low side of the RH% range (40% and not 50%). This gives us a little head room to fight that initial RH spike.

Here is a graph showing one of my flowering rooms when the lights go off at 3:45 AM in this case.

View attachment 4431167

You can see the temps drop and the RH% spike. In my rooms the dehumidification creates heat and when the room hits 80 my intake (cold dry air) runs it down to 75F to push some humidity out but not get it so cool that the dehumidifiers don't work. As you can see it's a balancing act. When my plants are at peak drink the dehumidifiers require some help from my ventilation, good thing I live in a fucking desert with low RH% lol.

I hope that helps make sense of the situation.

If the humidity gets below 40%, 35% for sure then the powdery mildew spores propagate easily so we want to avoid the RH% getting too low as well as too high. PM really thrives when it has the cool humid times and the warm dry times. So regardless of lights on or off we want to keep the rh% between 40 and 50 percent, ideally 40 and 45% but it's nearly impossible for most to keep the window that precise so I say 40 - 50% being realistic. Maybe 38 to 48 is more ideal. Accurate hygrometers that respond quickly are very much required.

Now, when lights go off the humidity generally spikes and we want to avoid this pushing us outside the target range. So when the lights are about to go off it would be ideal if we are on the low side of the RH% range (40% and not 50%). This gives us a little head room to fight that initial RH spike.

Here is a graph showing one of my flowering rooms when the lights go off at 3:45 AM in this case.

View attachment 4431167

You can see the temps drop and the RH% spike. In my rooms the dehumidification creates heat and when the room hits 80 my intake (cold dry air) runs it down to 75F to push some humidity out but not get it so cool that the dehumidifiers don't work. As you can see it's a balancing act. When my plants are at peak drink the dehumidifiers require some help from my ventilation, good thing I live in a fucking desert with low RH% lol.

I hope that helps make sense of the situation.

Perhaps you can help. I previously had a outbreak of PM and lost my entire harvest. I bleached the entire room, heated at 110 degrees for 2hrs, wrapped panda film on the ceiling, walls and floor. I have one 20" fan for fresh air intake pulling air through a allergen filter, a 16" oscillating fan in the room and a 6" exhaust fan. I use a mist humidifier and the PM is back, on my auto's.
I failed to mention that on my previous grow that I tossed out I fought it through veg into flower. I used hydrogen peroxide foliage application, green Cure, baking soda and it only kept it at bay. But 6wks into flower the Green Cure destroyed the pistols, the cola's no longer produced trichs so outta frustration I tossed it.
Back to my current grow I'm at a loss. This time I just pinch the leaves and remove from the grow. I began turning off the humidifier last night but still noticed PM but not as bad. Heres a view of the RH and temps. Ive been leaving my fans on regardless of lights on or off. Tonight I increased my electric heater to 78f so that the temperature stays about the same as when lights are on. Would it help if I turn off the air circulation to keep the PM from spreading during lights off? Any help would be great and extremely appreciated. Thanks

 

[trambles]

The dreaded PM. I've lived with it for several years. I've bleached, burned sulfur etc but it always comes back.
The only thing I have had success with is Eagle 20. I douse the plants a week before I flip to flower. It keeps the PM away for about 6 weeks. In my last couple weeks of flower I always start seeing the PM. I then spot treat with neem oil.
Dilute the Eagle 20 to 5ml/gallon. I always suit up in a painters suit, boot protectors, canister respirator, gloves and goggles. This shit STINKS terribly so if u are growing in the house I recommend taking the plants outside to spray. I'm in my garage so that's not an issue for me but the odor lingers for a couple days.
Nothing else, neem, sm90, milk, peroxide, sulfur, nothing, will eliminate PM. All it's doing is getting rid of the PM on the surface it will ALWAYS come back.

 

[Grandpapy]

The dreaded PM. I've lived with it for several years. I've bleached, burned sulfur etc but it always comes back.
The only thing I have had success with is Eagle 20. I douse the plants a week before I flip to flower. It keeps the PM away for about 6 weeks. In my last couple weeks of flower I always start seeing the PM. I then spot treat with neem oil.
Dilute the Eagle 20 to 5ml/gallon. I always suit up in a painters suit, boot protectors, canister respirator, gloves and goggles. This shit STINKS terribly so if u are growing in the house I recommend taking the plants outside to spray. I'm in my garage so that's not an issue for me but the odor lingers for a couple days.
Nothing else, neem, sm90, milk, peroxide, sulfur, nothing, will eliminate PM. All it's doing is getting rid of the PM on the surface it will ALWAYS come back.

Was this a recent purchase? I cant find sm90 anywhere.

 

[etruthfx]

Well I can offer you some insight as I've helped family members get rid of it before. Like everyone else said you want to keep room humidity low and have plenty of airflow, spread your plants out so all the leaves are not touching. After you have the environment under control you still need to eliminate the problem. I see other users mention Eagle 20. I have to admit I have used it and it works wonders. It has its pros and cons and here they are:

Eagle 20 when burned is a cancer causing carcinogen and will show up in lab tests. All chemicals have a half life, they don't stay in the plant forever sometimes you have to do what you got to to take care of a problem. It's not super expensive in the fact that you use VERY small dosage, I mean 2-3ml. per gallon literally only a few drops and It will wipe it out the first time. I suggest to only use it on fresh plants so it has time to flush. Never use in flowering whatsoever. You can use other organic remedies but they are not going to work the same. Lost Coast Plant Therapy is what I currently use for mite protection and it says it also takes care of PM aswell, worth using.

 

[Couch_Lock]

The first problem I saw, before PM was brought up, is the EXHAUST you use is 6" and the INTAKE is also 6". You won't get negative pressure in the tent, this will affect RH. Twice as much, or more, exhaust CFM you want. Tent front door should look at least slightly sucked in.

NEVER had PM but I just googled the cure:

"Combine one tablespoon baking soda and one-half teaspoon of liquid, non-detergent soap with one gallon of water, and spray the mixture liberally on the plants. Mouthwash. The mouthwash you may use on a daily basis for killing the germs in your mouth can also be effective at killing powdery mildew spores."

 

[Bourbon 2]

The first problem I saw, before PM was brought up, is the EXHAUST you use is 6" and the INTAKE is also 6". You won't get negative pressure in the tent, this will affect RH. Twice as much, or more, exhaust CFM you want. Tent front door should look at least slightly sucked in.

NEVER had PM but I just googled the cure:

"Combine one tablespoon baking soda and one-half teaspoon of liquid, non-detergent soap with one gallon of water, and spray the mixture liberally on the plants. Mouthwash. The mouthwash you may use on a daily basis for killing the germs in your mouth can also be effective at killing powdery mildew spores."

I've tried this spray application before and had 0 results. I had negative pressure when I started in the room after I lined it with panda film, it was pulling the panda film inwards so I knew that I was at negative pressure but lo and behold PM began to develop. Heck I even took precautionary measures by spraying them with neem oil twice a week. So at that point I cut in a return grill assembly with a allergen filter and began using it as a fresh air intake. This pm seems to be producing at lights off.
I noticed a reduction in growth when I began turning off the humidifier during lights off. Last night I tried turning up the electric heater thinking that would help but it seemed worse. So I'm truly at a loss. These 5 plants that have PM are auto's that are 5wks in flower. One additional thing I tried last night 4 hrs before lights out was I sprayed only the affected leaves with neem oil and it didn't work. The balance of plants in the room shows no signs of PM.
The pm is showing up on random fan leaves and on sugar leaves near the buds but hasn't gotten on the buds "yet". I'm concerned about spraying anything near the bud sites because of my experience I had on my previous grow. I've spent lots of money and time I hate to forfeit it