I have been dealing with pm in my garden since November 2017. I have a 3K bloom room with 48 plants on perpetual, and a 1k veg room with also around 48 plants and moms in various stages. The internet and this community has been my only source for information and support and I am grateful for it, but many of the suggestions, opinions, experiences of others I have found to be simply not true. Believing in the community I have followed the advice, spending much time, money, and loss of crops. This thread is a complete report of all the steps I have taken in the past, and continue to take in the future, until the powdery mildew is not existing in my grow, or I stop growing by the end of this year. It is a place for me to vent, but also if someone else finds this, hopefully they don't go through what I have in the last 8 months and counting. I think for something that is so devastaing and severe there seems to be not a lot of post and threads about peoples experience. Sure you find people asking for advice, and then people giving it, but there is not summary to the event. How are we supposed to learn anything!
The reason why some solutions don't work for everyone else is the environment and growing style is different. There are different species of PM that behave differently. Not everyone understands the full life cycle of PM (I don't either fully, but more than most I would safely say), so based on your growing style/environement you where lucky enough to possible break the cycle of spore reproduction.
It showed up after growing for 1 year already, I had never taken in clones and started everything from seed. I had 4 strains I was working with at this point and had run 4 other strains previously when I didn't have pm yet. Throughout this time I had many many unhealthy plants as I was a newbie making all the major mistakes.
When I noticed it on one plant my environment RH was in the 60s at night as it is winter here and -30C outside some days, and I don't have any exterior venting so I recirculate all exhaust air throughout my house. The plant that got it first was not very healthy was in the corner possibly not getting a lot of direct airflow and the lights off temp was in the 60's RH and 55-65F.
For suggested solutions It can be broken down into several areas:
Various Sprays for Control only
Environmental - Airflow, RH, Temperatures of lights on/off cycle Light
Healthy plants with good immune systems
Regular Sulfur burns
Killing PM within the plant with Eagle20 or MELTATOX
Heres a timeline of what I have gone through
***Sprays of Bakin soda,Vinegar,Milk
This made the flowers look very ugly and smell really bad and it didn't stop it for very long
Removed up to 2/3 of lower part of plants in some cases. Removed all fan leaves leaving only 3-4 colas. This stunted the plant and it ended up not doing anything for the last 5 weeks of flowering. Still got pm
I got 2 Hurricane wall mount oscillating fans on each end turned on max setting.I have PM on areas that are right in front of the fan getting hit with literally a hurricane of wind nonstop, I actually think this amount of wind is causing stress
*** Greencure Spray
This was the best performing spray and I was able to dilute it at 10 ml per gallon without burning the pistils anymore I would notice it come back 4-5 days later. This is not a long term solution for 48 plants for someone that has a disability. It is hard for me to walk, I can't spray plants in the bloom room as its finished hard wood flooring, so I need to take each plant into the bathroom bathub, spray down top to bottom, let it dry and bring it back in. Even when I sprayed plants every week on a regular basis, or as it showed up, I found that plants will have PM on the inside of the buds on all the little sugar leaves that are tucked away. So even if it looks like things are going will and you notice no pm on big fan leaves or outside leaves once you harvest and break open the colas you will find pm tucked away.
***Increase plant space & Light per plant
Reduced amount of plants from 4 by 4 per 1K light to 3 by 3 to increase airflow around plants, not have them touching so much and give maximum light. I still have PM on areas that are 20" from a 1000W HPS
This is what was most commonly suggested as an environmental solution. After having had 35-45% RH over the last 2 months I can say that this has not stopped the PM strain that I have) It is spreading just as fierce as when RH was 50-70!
***Eliminated Lights on/off Temp drop.
This summer I was hoping I would remove pm because of the RH and temp, as I have my lights on at 10 PM, so it is around 80F during the day when the lights are off, and then 80F at night, pulling in cool air from the open window. So there is literally no RH or Temp drop between light on off cycles. Unfortunately the PM is as strong as ever
***Grown different Strains
one strain has been 100% immune to pm - Critcal Cheese - very sativa, ofcourse those cuttings had to die on me! Others are fairly resiliant, where it can show up on a few lower leaves but once they are removed it doesn't continue to spread to the top parts.
Agent orange - all 4 phenos are prone
Headbanger - 1/4 phenos is almost immune, 1/4 is somewhat resilient, 2/4 are magnets - I had to toss the whole plant
Scotts og 3/3 are magnets
SSDD 2/3 is a magnet, 1/3 is somewhat resilient
So this is a highly debated product due to the unknown side effects of myclobutanil. But it was touted as the final and ultimate destruction of PM. It is stated that if used 9 weeks prior to harvest, it has not shown up in tested samples. The halflife is also stated as 4 or so weeks, so that would make sense. But again, Im not saying anything, other than that people said it cured their PM once and for all.
I diluted at 2.5ml per gallon, and dunked plants 100% underwater in a bucket for 30 seconds on DAY 1 of bloom. I have seen pm on these exact plants in as little as 3 weeks later. Since then I have continued to do side by side tests with single plants treated with Eagle20, and they all had pm in the end. I do think the pm was removed, but after 3 weeks the eagle20 was not in plant anymore in high enough concentration and it got re infected. Also for anyone that has negative comments and wants to ridicule me, remember, that by people being able to openly have a discussion about these products we can get to the truth, so that someone else might not resort to these products if he sees that it is not effective in all cases, I only followed the advice of the community that got me to eagle 20.
Have read this a lot, that healthy plants with a good immune system can fight it off. So I switched from pro mix, pure blend pro, to a organic living soil, with weekly compost teas and really tried to grow healthy plants. I just completed this step and had 4 plants on day 21, that were very healthy, and they all have pm. Silicate is also a recommended product for strengthening the plant cell walls and that has been in my resevoir for all plants still receiving pure blend pro nutrients. Healthy plants may make a difference if they havent been infected yet possibly, but if the mom had pm and its already inside the clones, then it is my experience that the health or state of a plant will not make a difference.
A lot of you will read what Ive been through and say, the only way to get rid of it is to kill all your plants, shut down your grow, sulfur burn, take all equipment apart bleach everything in the room, fans, filters,walls floors, ballasts,bulbs,pots,watering containers, throw out all your soil. Then start fresh with seeds.
Several reasons I have not done that yet:
1. I was following all the other advice first to see if I can manage the PM and even live with it to some degree and keep it in check.
2. These PM spores are everywhere in the trillions, they go 1/4 inch into all surface pores like drywall, carpets, wood. Even if I was able to clean and disinfect 95% of all surfaces in the room. Whats 5% of a trillion spores? exactly. Because the exhaust air from the veg and bloom room also circulate throughout the house my whole house has pm spores.
3. I started from seed originally, so this wasn't brought in through clone stock. It was simply in my home. I don't have AC so my windows and doors are open to let a breeze through the house in summer. Thats not something that I can change so even if I removed every trace and was succesful there is no guarantee for how long until this happened again.
4. I have spent the last year building up my organic living soil with my own compost and EWC, and $1000 of amendments, to only throw it out and get PRo mix and pure blend pro?
5. I have spent a year just to grow out these 4 strains, get females, flower them out, and keep moms of my favourite phenotypes. Im not a big shot grower who has access to hundreds of breeder packs or buddies who can give him the top 10 cuts circulating. I spent all my savings on these packs with the intention of finding a keeper and running it for years until I was bored with it. I haven't had 1 solid run with any of them yet really.
6. Ive had quite the challenge trying to grow for the last 2 years almost, and with my disabily and no income this hobby is becoming very hard to continue. If I was going to kill everything and start over I would probably just completely stop for the time being.
Sulfur burning is not a permanent solution from what I have read. It has to be done every week or two, and if you do it past week 4 in bloom the flower will taste like it.
I will continue to try these methods of healthy plants and see if the summer RH / temperature changes anything, I also have new genetics in the pipeline so I will flower just 1 phenotype to see how it holds up to the PM. No more putting 16 plants of 1 pheno into flower just to have it all covered in pm.
Once I have flowered all the seedlings I currently have I will stop bloom room until its empty.
Then I will:
Raise temps to 100F+ for 3 hours(supposedly kills spore)
Bleach whole bloom & veg room and equipment
sulfur burn once per week in veg and bloom room
Every Week dunk all moms in Meltatox & Eagle 20 (seperately 4 days apart)
Basically do this for a whole month, The idea is that the meltatox/eagle 20 will cure the plants from pm, and that the cleaning/heat/sulfur will kill all spores on contact for that whole month. By the end of the month the life cycle of the pm and the spores will be broken and I can start vegging and taking clones again.
And to add to this strategy of breaking this cycle - I would focus for half a year or more only on growing the strains that I found were immune/very resistant to pm in the past. I would have 6 months where even if there were some spores still flying around, these resistant strains would not get infected and give a chance for all the spores to die.
A lot of advice given is for prevention, and completely useless to deal with pm outbreak.
My thought is that yes there are always some spores floating around naturally from outside and plants can defend against these attacks every so often. That's why I had no issues for a whole year. But once the spores are reproduced in the grow room and are in the trillions, plants can't defend against those repeated attacks.
If you have something meaningful to contribute please do. I would like to read more successful and unsuccessful experiences from people so that we can learn from them. If you have any podcasts or academic trials/ studies, or pm specialist articles in the mater that material will help me and everyone else learn more about the life cycle of pm.
3 Scotts OG that are the latest victims to pm. Never had to spray greencure and saw no pm, a few spots on lower bud leaves, harvested the 1st plant and pm is all inside the flowers.
2nd Row all 4 are I would call healthy. nice green, strong stem, they are small so the 4 are not crowded in that row. Close to the 1000W Bulb, getting a tonne of air directly on the entire plant. ALL are getting hit hard with PM