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Citric acid foliar spray for powdery mildew?

Tynehead Tom

Active member
This is utter nonsense. Sulfur to control pm is well established and something everyone knows about. It is used by every commercial tomato and cucumber greenhouse and has been for a long time.

This thread was supposed to be about citric acid for this purpose. Less well known or at least more recently adopted. Maybe not as effective but also has some benefits.
I've been waiting for the citric acid discussion to continue but it hasn't.
I agree with keeping that discussion open and rolling along as it would be excellent to prove out something growers can use during flower. Hypochlorous (spelling?) Acid is another one that many are diving into and I follow those discussions as well.
Many products can assist the plant in resisting PM but no product I have seen or tried actually eradicated it from the localized environment..... not a single one. Until I took the chance and tried the sulphur spray.

Yes, gardeners have been deploying sulphur in various methods to try and "control" PM.
Sulphur burners/foggers in grow rooms have been used for years n years but yet the PM would return. That is because those forms of using sulphur do not present it to the plant in a form that kills the parasite.
Neems and other oils only provide a barrier of protection , they do not kill the parasite.
Baking Soda sprays raise surface PH which is beneficial to apply to fusariums but Baking soda soes not kill PM though it does.... like neems and other oils, provide an unfavorable coating on the leaf that the spores will have a hard time infecting the tissue. These products have thier place but they do no eradicate the parasite, they only delay infection and delay fruiting.

We can run around in circles here for those that are seemingly in denial but there's no need for that.
I grow in a harsh climate here at 52N, 3000ft elevation , in western Canada where everything is trying to infest or kill my cannabis plants. Growing here is a challenge and I have to practice light dep to run the multi strain gardens I run. My greenhouse is basically a cold frame as it is just wood covered in plastic with lots of open spots. There is no exhaust system , just 2 cheap 16" oscillating fans. The plants get shoved into a 12x12 shed with no intake or exhaust, just those two fans. To say that I provide the optimal conditions for fusarium, boytris, and especially PM would be an understatement. I have struggled with these pathogens before in my grows posted online.
My grow threads these days are on overgrow and I don't have one here this year but if anyone followed last years grow and this years..... they would see what I am talking about.

I had a PM infestation last season in the grow room and at the tail end of my out greenhouse run. I nearly lost my marbles as I had not seen Powdery Mildew on my plants since the early 2000's when all we could do was cut and burn and bleach everything and then run commerical ozone generators to sanitize equipment and grow rooms. Anyways...... if I follow the arguments in this thread that PM is systemic and that all these other products mentioned are better than micronized sulpjur spray....... it only stands to reason that I would still have PM and that I am lying to you all for sport...... right?
Well, I have a 100% PM free garden inside and out after perfoming spray downs in the fall inside and out and repeating the same this spring. That is two applications of micronized sulphur spray used as directed by JoeCrowe ...... and that systemic PM is mysteriously no where to be found..... and I've looked hard for it. It ain't there..
and ounce of Cure is worth how many ounces of Prevention???? You guys tell me LOL
 

Tynehead Tom

Active member
My V1F3 of Karma Genetics original version of Biker Kush.
11 weeks of light dep in my shoddy set up and no PM to be found. She has not received a single foilar spray except for one application of sulphur spray back in June when she was a youngster.
She is one of the last 7 plants in my greenhouse to get the chop and even with perfect PM conditions.... it just ain't there.
2023-10-08 Biker Kush V1F3 #3 pic 1 - Copy.JPG


2023-10-08 Biker Kush V1F3 #3 pic 2 - Copy.JPG


2023-10-08 Biker Kush V1F3 #3 pic 3 - Copy.JPG


nobody around here grows 11 week strains outside LOL and they all think I'm nuts in doing so..... but there it is..... and PM free to boot ;)
 

xtsho

Active member
I've used citric acid as a contact killer for mites. It's also effective on PM if it's visibly present as a spot treatment. The low pH creates an environment that is inhospitable for the PM to survive. I don't think it lasts though so I use a preventative of potassium silicate and sesame oil on plants outdoors.

I've never had PM indoors but I have been doing preventive spraying for years. I stop once the plants start flowering but I think the residual potassium silicate and sesame oil left on the leaves keeps working. I still have plants outdoors and I'm in the PNW. Not a spot of PM anywhere in the yard on any plants thanks to weekly preventative spraying.

Following an IPM regimen can eliminate many headaches. It has for me.


So, no one has mentioned using silica. Some will say that PM is virtually nonexistent if silica is used.
Getting ready to buy some more and finding all kinds of new products such as Power Si. Mammoth has one too that's a bit cheaper. These products are not sucker products either as many pros use them. Will do more research before I buy, but one feature stood out for me with the newer products: no pH drift.

I eradicated powdery mildew using a foliar of Agsil potassium silicate and sesame oil. It's prevented PM on all of my outdoor plants not just the cannabis. I haven't had PM in years on any of the the PM magnets in my garden like Squashes, cucumbers, roses, etc... I do foliar weekly around the yard during the growing season. I stop on the cannabis once they start flowering.

I don't pay for fancy brands as I can get potassium silicate down the road at Concentrates for $12 a pound. Same stuff but in powder form and much more product since it hasn't been watered down and put in expensive packaging. I have sesame oil in the kitchen cupboard as I use it for cooking so I always have that around. Organicide 3 in 1 has sesame oil as it's active ingredient. Sesame oil is a bee safe pesticide.

One pound of potassium silicate will make at least a hundred gallons of foliar spray. There are places selling it online but with shipping the cost is closer to $30 a pound.
 

sdd420

Active member
I've used citric acid as a contact killer for mites. It's also effective on PM if it's visibly present as a spot treatment. The low pH creates an environment that is inhospitable for the PM to survive. I don't think it lasts though so I use a preventative of potassium silicate and sesame oil on plants outdoors.

I've never had PM indoors but I have been doing preventive spraying for years. I stop once the plants start flowering but I think the residual potassium silicate and sesame oil left on the leaves keeps working. I still have plants outdoors and I'm in the PNW. Not a spot of PM anywhere in the yard on any plants thanks to weekly preventative spraying.

Following an IPM regimen can eliminate many headaches. It has for me.




I eradicated powdery mildew using a foliar of Agsil potassium silicate and sesame oil. It's prevented PM on all of my outdoor plants not just the cannabis. I haven't had PM in years on any of the the PM magnets in my garden like Squashes, cucumbers, roses, etc... I do foliar weekly around the yard during the growing season. I stop on the cannabis once they start flowering.

I don't pay for fancy brands as I can get potassium silicate down the road at Concentrates for $12 a pound. Same stuff but in powder form and much more product since it hasn't been watered down and put in expensive packaging. I have sesame oil in the kitchen cupboard as I use it for cooking so I always have that around. Organicide 3 in 1 has sesame oil as it's active ingredient. Sesame oil is a bee safe pesticide.

One pound of potassium silicate will make at least a hundred gallons of foliar spray. There are places selling it online but with shipping the cost is closer to $30 a pound.
How do the plants like it? Is it better than spraying sulfur?
 

Limeygreen

Active member
Bacillus subtilis will not kill leaf tissue, I have used for years, it works well with milstop combined as preventative.

Sulfur pots work well, use pipe sulfur or lump sulfur it will go to liquid in the pot, works great if you use micronized sulfur it doesn't work well and burns to a hard lump in the pot.

Spraying sulfur will work very well, 0.7-0.8 grammes per litre of micronized sulfur is all you need, not the 15 grammes that safers says. Treat once a month on mums or veg plants, rinse off with aloe water the next day. Why aloe water, it helps pull off the sulfur residue without burning the plants or trapping the sulfur.

@flower~power Watch out spraying lost coast after sulfur, or any oil after sulfur, it will trap the sulfur under and with the oil in light act like a magnifying glass, burn your crop. I did lost coast then skipped a couple days then sulfur with no issues.
 

HorseBadoritiz

Active member
Tynehead Tom has it right, cheap micronized sulfur available at any garden shop or Amazon, 1 TBS/Gallon. PM will be KILLED. Outdoors, spray the area, and vegging plants, then again in two weeks just to get whatever you missed the first time. Indoors remove any plant detritus, spray veggers twice... it's gone, gone, gone.

I have a perpetual in a dirt floored, block walled crawlspace, no way to sanitize. Had PM for 3 years. Tried milk, citric acid, potassium bicarb, SM-90, hi-powered UV-C, Calcium w/ Aminos, and anything else I read about.... I could vaguely control it, but never eliminate it.

Tried JoeCrowe's sulfur treatment last Feb. Soaked all veggers til dripping, then again two weeks later... haven't seen any pm since.

It's not systemic, it doesn't travel by wind, needs to be carried on infected material.

Not for flowers, unless you like the taste of rotten eggs.

It's a death sentence for pm.

ETA If you used any oil-based sprays, wait 2 weeks before using sulfur... it will burn the plants.
 

flower~power

~Star~Crash~
ICMag Supporter
Bacillus subtilis will not kill leaf tissue, I have used for years, it works well with milstop combined as preventative.

Sulfur pots work well, use pipe sulfur or lump sulfur it will go to liquid in the pot, works great if you use micronized sulfur it doesn't work well and burns to a hard lump in the pot.

Spraying sulfur will work very well, 0.7-0.8 grammes per litre of micronized sulfur is all you need, not the 15 grammes that safers says. Treat once a month on mums or veg plants, rinse off with aloe water the next day. Why aloe water, it helps pull off the sulfur residue without burning the plants or trapping the sulfur.

@flower~power Watch out spraying lost coast after sulfur, or any oil after sulfur, it will trap the sulfur under and with the oil in light act like a magnifying glass, burn your crop. I did lost coast then skipped a couple days then sulfur with no issues.
Well if you can’t combine it with continuing care of the horticulture oil and you can’t use sulfur into flower I’ve got a problem
 

Limeygreen

Active member
@flower~power You can resume oil 21 days later, one member posted 14 days, so trial and error if you like. Some commercial growers of cannabis told me they spraying before into flower with sulfur then that's it, treat mums and veg plants with it monthly otherwise. Could always try the most mildew susceptible variety first on a smaller plant if you can spare the space and see what happens with your rotation.
 

Tynehead Tom

Active member
Bacillus subtilis will not kill leaf tissue, I have used for years, it works well with milstop combined as preventative.

Sulfur pots work well, use pipe sulfur or lump sulfur it will go to liquid in the pot, works great if you use micronized sulfur it doesn't work well and burns to a hard lump in the pot.

Spraying sulfur will work very well, 0.7-0.8 grammes per litre of micronized sulfur is all you need, not the 15 grammes that safers says. Treat once a month on mums or veg plants, rinse off with aloe water the next day. Why aloe water, it helps pull off the sulfur residue without burning the plants or trapping the sulfur.

@flower~power Watch out spraying lost coast after sulfur, or any oil after sulfur, it will trap the sulfur under and with the oil in light act like a magnifying glass, burn your crop. I did lost coast then skipped a couple days then sulfur with no issues.
excellent advice in this post too. Especially regarding NOT spraying anything with oils before or after using the sulphur spray. I should have included that with my posts.

I used Serenade which in Canada was name changed to Natria and is the same product with the Bacillus subtilis. When i used it I was fighting Fusarium which I first held at bay with baking soda spray but defeated it with the Natria. I had burned leaves where it contacted the leaves closer to the stem. Perhaps it was a reaction from residual baking soda? Not sure but I observed it as possibly harmful to leaves so sprayed stems only. It's only now that I am wondering if it was a reaction between the natria and the baking soda that burnt the leaves and not the natria by itself.
 

flower~power

~Star~Crash~
ICMag Supporter
we’ll see what happens.. the plants I intend to put in the room are perfect and blemish free at the moment I want to keep them that way this may be a good opportunity for me to clean the room strip it down ..etc
 

xtsho

Active member
How do the plants like it? Is it better than spraying sulfur?

The potassium silicate/sesame oil has no effect on the plants that I've noticed except. I haven't used sulfur except for garlic/onion extracts. I've never used any sulfur product except for lowering the soil pH for my blueberries. Citric acid will burn the foliage if use at too high of a percentage.


Nukem and suff x oil. Full rates. Mixed together. Makes an Anti pm and sucking bug prevention that lasts 3 or 4 days. Bugs, pm, anything. It works wonders. Been using it for years

Nukem is good stuff for mites. It's citric acid based. It's not going to be a PM preventative but it will work for a spot treatment once it's present. I recommend it for mites in flower as it doesn't contain any oils which you don't want to be spraying at that point. I am a little biased as it's a local company headquartered just a few miles from me. The company Flying Skull also puts out a good 3 part nutrient.
 

HorseBadoritiz

Active member
"the plants I intend to put in the room are perfect and blemish free at the moment I want to keep them that way"

If they are in veg, and you haven't used any oils for a couple of weeks, you should be good.

I lied when I said I used the sulfur in Feb of 2023, it was 2022! Time flies when you don't have pm to drag you down!

I can't grow weed outside, but we have zinnias, bee balm, squash, peas, and a bunch of other stuff out there.They are all pm magnets for us. I sprayed sulfur on all those areas at the same time, no pm on anything again this year.

There's different types of pm that are plant specific, zinnia pm doesn't effect squash for example. Joe still hasn't figured out which one likes cannabis, but has ruled both of those out.
 

Limeygreen

Active member
excellent advice in this post too. Especially regarding NOT spraying anything with oils before or after using the sulphur spray. I should have included that with my posts.

I used Serenade which in Canada was name changed to Natria and is the same product with the Bacillus subtilis. When i used it I was fighting Fusarium which I first held at bay with baking soda spray but defeated it with the Natria. I had burned leaves where it contacted the leaves closer to the stem. Perhaps it was a reaction from residual baking soda? Not sure but I observed it as possibly harmful to leaves so sprayed stems only. It's only now that I am wondering if it was a reaction between the natria and the baking soda that burnt the leaves and not the natria by itself.
I used to mix with potassium bicarbonate at 1 gm per litre, pretty low using rhapsody, different formulation. 850 litres of water per acre if that helps. I heard of people using label rate of milstop and could see some phyto because rhapsody has spread sticker in it already.
 

Ca++

Active member
Serenade or Natria after rebranding..... is an effective spray to treat Fusarium and if caught early can offer excellent results. I am not aware of it being used for Powdery Mildew on Cannabis. Tried a leaf test with serenade/natria and it killed the leaf. The stuff is meant to be sprayed on stem tissue not leaves.
I would not even attempt to use it on Powdery Mildew as it is really not meant for that.
On some crops it's only 50% effective for PM, but it's pretty good on canna. It's fine on leaves, and even strawberries. Bacteria isn't likely to burn anything. It just eats the PM, then dies when there is no PM left. Though it's main use is prepping against bud mold in field situations. Where rain at the wrong time, is worth taking out insurance against.

Nobody has spoke about rice hulls. Bugbee will put them in anything he can. It's the already mentioned silicon, in an easy to dose method.

The Athena IPM looks a lot like Trifecta Crop Control. Nano-sized essential oils and soap. Treats and prevents molds, mildews, pests, and parasitic species. The active ingredients are thyme oil, clove oil, garlic oil, peppermint oil, corn oil, rosemary oil, geraniol, and citric acid. Inert ingredients include filtered water, soap, isopropyl alcohol, and vinegar.


I notice the topic of sulphur and oils not mixing, is often presented differently. I would have to seek more professional advice on that topic. We don't seem to have a common consensus across the forums.
 

Verdant Whisperer

Active member
For the first few weeks it’s no problemo, after resin starts the sulfur sticks to the resin and you can’t wash it off.

I was using a combination of sulfur and peroxide to keep it at bay for a while. Now this Athena is way better.

It kinda had the same effect as the sulfur where if a spot pops back up the mildew won’t be able to spread much further. I think it’s the ph of the leaf due to the citric acid, as opposed to the sulfur leaving micronized residues.

I’m perpetual so I totally understand the situation.

Game changer
View attachment 18901180

I tried Regalia and it didn’t work either
Looks good but for the price there selling it might be worth buying oils and citric acid separately and mixing when using.
 

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