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medmanmike

Powdery Mildew?

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I got the results back from testing samples of my latest harvest.  Cannabinoid profile was great, but a digital microscopy analysis shows PM.  See attached.

 

I'm familiar with PM in the vegetable garden et al, but have not had it in the grow room.  I visually inspected the plants on a regular basis throughout the grow and did not see any evidence of PM.  Room temps fluctuated between 68-81 F and RH 45-55%.

 

I would appreciate it if you've had experience with PM to look this pics over and let me know what you think.  The areas of concern are inside the red box.  

 

I've got a call into the lab to see if they will quantify the severity of the infection.  The next question is, can it be consumed?  

 

My research shows PM is non-toxic to humans, but it can cause respiratory problems if inhaled.  Some eople have suggested making oil out of it.

 

Thanks in advance!

 

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Looks bad.

 

I see this a lot on outdoor grown cannabis. Late in the season when you are deciding whether or not to harvest yet. Then the pm starts and you have to hurry and take it all down as fast as you can to avoid total loss.

 

I saw it one time on my indoor grown cannabis. The one time I grew BigBud before I had better genetics. That strain would pm at the drop of a hat. It did it during drying too. One minute it looked perfect and the next it started to have pm. 

 

In my opinion it's trash now. Sorry for your loss. 

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Zap,  I've been vaping the N.Lights for about a week. Can't say I noticed anything different.  (I did get a new vape around this same time and I'm having difficulty getting use to it - gets to hot, burns the herb, etc.)  Could PM cause this?  I really don't think so, because the same thing happens with the vape when vaping previously harvested bud.  

 

Checking the cured/stored bud is next on my list. I sprayed the two standing SSH ladies with a milk spray this morning.  I can definitely see the PM on the leaves, but it's not widespread, nor overwhelming in quantity.

 

I am aware of "bud washing" techniques that use H2O2 in water to kill and remove the PM.  Normally, the wash is done prior to final trim, drying, etc.  I'm asking my mentor (who uses this method) if he thinks I could re-wash the dried bud in a H2O2 bath.  

 

I saw references on the web to making hash or oil if it's not to infected.

 

Rest, I have a call into the lab to ask them if they can quantify the severity of the PM. I will spend the time today checking the cured bud with a 60x loupe. Sure hope that I have some that is fine.  15 oz down the drain will be hard to take. I'm hoping I can salvage the SSH. Thxs to you both.

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 I can definitely see the PM on the leaves, but it's not widespread, nor overwhelming in quantity.

 

This stuff grows quickly. If it's on the leaves the plant is done for. It's a sign that nature is taking over the plant and it's time is done. When you see any PM anywhere on a plant it's time to hurry and salvage anything you can. If it's on one spot it's going to be everywhere soon. 

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Neem oil works great for controlling pm in veg.

So if you already have PM in veg you drag the whole moldy plant all the way through flower like that? To me this would be a waste of time. If the plant was in veg and already molding I would start over with a clean room, clean plants and adjust the conditions that caused the problem in the first place. Because adding more darkness, flower stage, would just make the chances of having more mold greater. 

Edited by Restorium2

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My strongest strain, Chem D. It doesn't put out much per plant but it's killer. I treasure it. One summer I had a full jar in a cabinet. My last jar of it. Plant count and all it's hard to justify growing very many because it takes a long time and it doesn't put out a lot. So I'm always right on the edge of running out of it. That last big jar of the most killer Chem D got a little moldy in the cabinet. It about killed me but it went down the garbage disposal. I still feel it, the loss. But I haven't made that mistake again since. 

Get rid of the moldy plants and buds. Figure out what went wrong. Adjust what you do. And never make that mistake again. Don't neem oil around it. Fix it for good. 

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I believe PM is systemic. So once you can see it, you know it's already present thoughout the plant.

 

I had the dreaded PM once. Luckily it was confined to the flower room and I caught it quickly. I harvested the affected plants that were ready for harvest and culled the others in the flower room. I kept the harvest for my own use because I'm not too worried about a little mold. I love moldy cheese. And in my normal line of work I'm exposed to much worse. I found no ill effects. I ended up giving a lot of it away for free to patients (with full disclosure) who also weren't worried about it. And I made some nice oil too.

 

As a precautionary measure to save some strains, I bought some Eagle 20 and sprayed some plants, waited a couple of weeks, took cuttings, and killed the sprayed plants. I also ended up culling those resulting clones because my other plants in veg never showed signs of PM.

 

The measures I implemented in the meantime (increased air circulation and dehumidifiers) did the trick.

 

If you look around your yard in the fall, odds are you'll see plants with PM. They are usually plants with big leaves. I see PM in my vegetable garden every year, always on the late finishing plants like pumpkins and squash. This emphasizes the need to change clothes before entering your controlled environment indoor garden. Myself, I usually do my indoor garden chores in the nude.

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I believe PM is systemic. So once you can see it, you know it's already present thoughout the plant.

 

I had the dreaded PM once. Luckily it was confined to the flower room and I caught it quickly. I harvested the affected plants that were ready for harvest and culled the others in the flower room. I kept the harvest for my own use because I'm not too worried about a little mold. I love moldy cheese. And in my normal line of work I'm exposed to much worse. I found no ill effects. I ended up giving a lot of it away for free to patients (with full disclosure) who also weren't worried about it. And I made some nice oil too.

 

As a precautionary measure to save some strains, I bought some Eagle 20 and sprayed some plants, waited a couple of weeks, took cuttings, and killed the sprayed plants. I also ended up culling those resulting clones because my other plants in veg never showed signs of PM.

 

The measures I implemented in the meantime (increased air circulation and dehumidifiers) did the trick.

 

If you look around your yard in the fall, odds are you'll see plants with PM. They are usually plants with big leaves. I see PM in my vegetable garden every year, always on the late finishing plants like pumpkins and squash. This emphasizes the need to change clothes before entering your controlled environment indoor garden. Myself, I usually do my indoor garden chores in the nude.

You be gittin' the curly hairs on da sticky buds man. Not a good ting.  :))

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So if you already have PM in veg you drag the whole moldy plant all the way through flower like that? To me this would be a waste of time. If the plant was in veg and already molding I would start over with a clean room, clean plants and adjust the conditions that caused the problem in the first place. Because adding more darkness, flower stage, would just make the chances of having more mold greater.

If its a strain worth keeping then yes I would try to contain it and change my room conditions to avoid a outbreak in the future. I have had pm once years ago and did save the plant effected and kept it for a couple years afterward.

Edited by Apollo

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If its a strain worth keeping then yes I would try to contain it and change my room conditions to avoid a outbreak in the future. I have had pm once years ago and did save the plant effected and kept it for a couple years afterward.

I can see that. Why I didn't go there was that I keep a dedicated mother grow room with one of each of my strains in it. If I had mold in my veg room then I would kill all the plants and take some more clones from the mother room and start over. The mother room is what helps me sleep at night, not as worried that I would lose a strain. I can't do as some here advise, take clones out of the veg room for the next crop. That seems like a recipe for losing a strain someday. I have some strains from the 80's. They are like the holy grail to me. Very important. 

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Bleach everything you can and run a sulfur burner. Treat every plant you have in veg with Eagle 20 fungicide. You typically don't want to run that product in flower. I believe it is like 60 days since last dose till crop. Systemic treatment that should serve you well. Also download and print out a VPD Chart and try to stay as close as you can with the proper zone. Powdery mildew will also thrive in low humidity daytime environments it isn't just all about it being too humid. I couldn't be more serious about having a VPD Chart on anyone's wall along with a couple of hygrometers. This also goes for when drying, mold will grow on your flowers if the humidity is too high in just that short period of time and show up on the lab analysis as well.

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It's strain related. You can grow two strains in the same room and one will mold and the other will not. You can dry two different strains in the same room and one will mold and one will not.

So there is no chart that works for everything. You have to know your strains, what they want, and what conditions will cause them to mold. 

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SB, thanks for your comments. I do have this chart, but I question its use as some of the RH numbers seem so high and so far outside of what one would consider the normal range(s) for cannabis. I'm assuming you use this? What do you run (temp / RH) mid/late flower? Anyone else out there who "adheres" to the VPd chart through out the grow cycle?

 

I've tried to reconcile using this chart but I just can't wrap my head around 70%RH at 77° F . Just seems like way to much humid. Just saying.

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That's what happens when you post things you read about and haven't even tried them.....  Fakeness. A real grower can see the fakeness. You can't fool an experienced grower with a chart full of fakeness. 

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Lots of fans. Temps at 80 f and below. No dense areas that are stagnated from the air flow. The air flow is the key. Buds can actually produce their own heat without air flow. The room can be 75 and the buds can be 90. The center of a dense bud can get very hot without air flow. 

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Put up a bunch of fans and ignore the humidity works for me and the strains I'm using now. It works year round. Lots of air movement. 

I just checked my humidity meters in my flower rooms. One says the range for the last 3 days was 21% - 24%, another reads a range of 21% to 31% (probably spilled some water to get it up to 31%). The air in the rooms are exchanged at the rate of 600 CFM. Plants are super healthy, humidity is low, and these rooms are in the basement. 

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I already typed all this on my ipad but of course since Steve Jobs is dead apple sucks now and I have to do it again.

So, this chart, if I am reading it right, indicates proper humidity between 65-85 percent if you are running 78 degrees in flower? How does the VPD relate to mold formation, and is it different for growing plants vs drying plants?

 

No, 78F max is 75%. All VPD is, is the difference between water in the air and max water at saturation in the air. Just a geek metric but vital for environmental conditions, ie: roots, leaves, stomata, xylem tubes. Too much water in the air you are susceptible to mold as well as too little. Growing plants we want to keep the water in the plant, drying plants we are removing water typically at 40% RH, you can do the Boveda packs after everything is stable and store for well over a year at 62% without fear of mold.

Is there a "safe" zone which will provide decent growing conditions for all strains, and avoid mold for all strains? I.e. when you are growing 10 strains in the same room, what setting should one use to ensure a decent harvest? Is it correlated with temperature like this, where the acceptable humidity increases with ambient temperature

Safe zones are 5-10% below Min RH. At 78F 60-65% is great, assuming 10 degree swing for night at 68F 50-55% is acceptable. That will easily work in multi variety rooms. Yes higher the temp the more water the air can hold. You don't necessarily want a "mountain" variety at max RH as say a "tropical". 

 

So relative humidity in the growroom, whether too high or too low, makes no difference to health of plants at all?

Nope, too high or too low will affect growth. Say too dry your plant will grow slooooooooow in veg or be stunted. Like when you are taking clones. You want high humidity so the plants can have the stomata open to take in moist air since there are no roots to uptake water. If you ran your room like that with condensation on the walls it would be a mold fest and the plants would not be drinking nutes they would be sucking moisture out of the air. I know you know this just typing this out for someone else's benefit that might not.

 

Right. That is what I have seen here in Michigan as well. A naturally-ventilated room will stay really low humidity in the winter. The possible problem comes when the plants are in a sealed room or tent, which can get the humidity up in the 60-70 percent range. Does this pose a risk of mold at normal flowering temps, 75-80 F?

No it doesnt, it is a problem when the lights go off and the plant is still transpiring and throwing off more water. That is where the A/C, dehumidifier comes into play 365 days a year. Also like you said the MI winters suck the moisture air out of the air. That is why people need to be running a HUMIDIFIER and arent.

 

FYI in a proper sealed room for every gallon of water you are throwing down you should be pulling 98% of a gallon of water out of the air via an A/C or Dehue. In the winter this is near impossible since it is so dry out and no ones room is really sealed 100% like that. That is why your A/C pulls little to no water out of the air in the winter which is why you need a dehue. Plus the plants know it is 20 degrees outside regardless of what we are doing inside.

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SB, thanks for your comments. I do have this chart, but I question its use as some of the RH numbers seem so high and so far outside of what one would consider the normal range(s) for cannabis. I'm assuming you use this? What do you run (temp / RH) mid/late flower? Anyone else out there who "adheres" to the VPd chart through out the grow cycle?

 

I've tried to reconcile using this chart but I just can't wrap my head around 70%RH at 77° F . Just seems like way to much humid. Just saying.

They might seem high because 90% of indoor growers really don't pay much mind to their enviro or learn how to manipulate the enviro till there is a problem. Err on the side of caution and run 5-10% below min RH according to the chart. The chart is a guide, it is variety dependent.

All through flower: Day 74F 63%, Night 64F 52%. That is for everything I would typically run, ie indica, sativa, hybrid, poly hybrid.

I'd make the chart part of your tools.

BTW that Eagle 20, mix it with the nutes I'd shy away from spraying plants with it.

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They might seem high because 90% of indoor growers really don't pay much mind to their enviro or learn how to manipulate the enviro till there is a problem. Err on the side of caution and run 5-10% below min RH according to the chart. The chart is a guide, it is variety dependent.

All through flower: Day 74F 63%, Night 64F 52%. That is for everything I would typically run, ie indica, sativa, hybrid, poly hybrid.

I'd make the chart part of your tools.

BTW that Eagle 20, mix it with the nutes I'd shy away from spraying plants with it.

That chart is total BS when it comes to marijuana. I don't know why you even posted it. If you actually grew marijuana then you would have just moved on after you looked at it once. Stick with Begonias. 

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