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PM will not go away. Harvesting early

After having issues with PM on my last couple grows, I really tried to make sure that it was in check this time. Even though I have done the below, at week 7 in flower I have noticed a small stripe of PM going the backside of each cola. I am about ready to clip early and send them into a peroxide bath. The PM is starting to creep into the buds. This is insanely frustrating. Below is all the info and what I have done.

  • 5 strains in 4x8x9 tent (4 blueberry cookies,1 durban poison, 1 amnesia lemon, 1 gmo cookies and 1 zero dark (cbd) all DWC and triple scrog’d and all lollipped to about 4 nodes from the top
  • Nutes AN Sensi Bloom @ 75% strength, Great White, Hydroguard, Big bud, Bud Candy, Silica, Beastie Bloomz, B-52
  • ppm at around 900 max, PH at 5.8-6.1, 3 gallons in each 5 gallon bucket, 8 inch disc airstone, 2 - 950GPH 8 outlet air pump, recirculating DWC
  • Cobb LED lighting using 640W off the wall pushing 2522.8 umol/m²s at 18 inches. 2 of them.
  • 2 12 inch oscillating fans blowing across the mids and tops
  • 2 15 inch vortex fans on bottom blowing upwards
  • 1 60L dehumidifier set to 40-45% RH
  • 2 AC INFINITY 6 inch inline fans, serial controlled, one as a push into tent from A/C’d room at around 68 degrees, the other is pull through a 351 CFM Australian Carbon air filter and out the top into ceiling that leads to duct outside. Temp sits around 75-80 degrees F while using C02. Tent has negative pressure
  • used greencure as a preventive in veg. Did not see PM at all till about week 4 of flower. Used Banish after that and PM was controlled for maybe 3 days. Since it keeps coming back I have been using Banish to keep it in control. I do not want to keep using it when nearing harvest.

After all this I am thinking about scrapping or seeing what I can salvage. The rooms and tents have been sterilized with sulfur. I do not want to use it while flowering. Any help would be appreciated. I don’t mind scrapping the grow, but I am afraid this is never going to end, so I am hesitant about my next and what I should do. It is possible that the plants could not fight off the PM naturally as I was only using root bennies and nothing like silica previously. Maybe I need to do some foliar feeding or something… Maybe a tea…

Thanks,

Matthew Earl - CannabisFTW

4 Likes

How long is your veg?

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Hey Joe!

My veg was about 4 weeks . Plant is now over 6ft. Attached is a picture of one cola out of maybe 15 colas. Also the base right before I finished defoliating the second tier of the scrog. I am not going to scrog like this again unless i have more space. This had constricted me very much.

Matthew Earl - CannabisFTW

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Those are some crazy trees for 4 weeks veg + 7 - Nice work!

Since PM is humidity related, I can only suggest to do what you can to reduce liquids in the room and maybe see how the plants do with less humidity.

If the PM is appearing close to the center of the plant, you might try making the cutout for the stalk as airtight as you can.

I say this because I learned that mold and PM problems go away when you have the least moisture in the room. I don’t mean RH, I mean liquids in the form of nutrients in media, on a table or in a tank - get it out of the room. For moisture to evaporate it has to go were? Through the canopy?

How big are your roots? Do you need 5 gallon pots?

Of course you’ve got a challenge doing that with DWC and you don’t have the infrared spectrum of HPS lighting, but I’ve seen this proven in tents that struggled in the summer to keep temps below 90F while many others just took a break.

2 Likes

Thanks Joe!

Actually the LED’s also have IR and UV in them (supplemental) I think you are spot on about the moisture in the room. I have some holes on the sides of the buckets that water may be evaporating out of. Also letting the bottom leaves fall off and let them shrivel up is a problem as I had a hard time reaching through all of it to get rid of em. My roots take the entire space of those buckets. They drink about 1 - 2 gallons of water a day. Sigh, I am going to do the next one coco. I like to switch back and forth. I am making a whole new 8 bucket under current dwc with a waterfall DO system to remove the airstones and air pumps. I need time to do it so I will do coco for this perpetual run.

Just FYI I have videos and such that I am posting up with DIY stuff and reviews. I don’t want to link it yet unless I am allowed. If people are interested in contributing and such I would love to discuss it more.

Here is half of the colas removed. All popcorn is in the front. Going to make edibles and oil with it. This is not a typical high yielding strain.

Thanks,

Matthew Earl - CannabisFTW

2 Likes

It will be interesting to see if the PM goes away with coco.
How do you feed with coco? What size pots do you use?

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Sensi Coco grow A/B. RO water. Voodoo Juice and B-52 early and late. I use 5 gallon smart pots. I used to use 2 gallon but root mass gets too big. Before, I grew many smaller plants. Now I do less with a little bigger plants. I get a bigger overall yield (when scrog’ing) with less nutrient use. I also use a silica and a bennie tea. I really like Voodoo Juice but you have to keep it refrigerated and use it before it expires. At least my experience or it will mold up. I also have the H&G line as well as GH. I have used them all and I really like the convenience of AN’s ph perfect stuff. Makes it easier as I am already dealing with a ton of other stuff. My bluelabs ph controller is now sitting in my lab’s closet. lol.

About my feeding, I would use the calculator, watering to 20% run off initially once a week, then using a 15% nute solution every 2 to 3 days. It is even ok to just use plain water between feedings.

Matthew Earl - CannabisFTW

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I have one GMO that has PM on it right now. Its because my stupid exhaust fan got disconnected in the night and humidity spiked to about 80%. PM or powdery mildew is not a systemic mold (it does not live inside the plant) it only survives on the surface of the leaves. Im using Dr.Zymes on it (foliar) and spray affected leaves. This stuff is so safe you can cure your athletes foot, you can drink it too, you can put it in your dogs ear and cure infections in there (look at Soil Kings review on it on Youtube Im not lying!). It can be used up to the day of harvest too.
Anyway, Ive been foliar spraying affected leaves and PM still pops up because if you leave one nook or cranny untreated then chances are PM will come back. You can use DR.Zymes to clean walls too. The thing is since its been coming back for you, youll need to clean lights, fans, everything. Now im probably going to have to do that too.
Another thing is make sure to defoliate leaves that overlap each other. When you dont, moisture gets trapped in that closed spot creating micro climates and humidity in that small bubble is 100%. Go find leaves that are “glued” together and pry them open. Youll probably see water underneath and or PM there. A good way to avoid this is to also have alot of air movement in the tent because PM hates airmovent and prefers stale air.

4 Likes

Hey sponge!

Thanks for the advice. Can Dr.Zymes be used with light on? Or even lights off for less than an hour? Most that I have seen need lights out for at least 2 or more hours after use, or it will cause light burn and brown pistils.

Thanks,

Matthew Earl - CannabisFTW

3 Likes

Yeah light off for 2 hours. Any foliar, in flower, will probably turn pistils brown but pistils dont have any thc or what we grow the plant for anyways. If you use that as an indicator of when to harvest then use a microscope to look at trichome heads.

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Yeah I have a loupe and a digital microscope. I guess I just want to be “picture” perfect. I want a yield with the exact representation of it growing correctly. I am OCD like that. It causes me headaches than not, that is for sure. I will check it out. Thanks sponge.

Matthew Earl - CannabisFTW

3 Likes