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Actually KILLING powdery mildew

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    Actually KILLING powdery mildew

    Powdery Mildew (PM) is a systemic problem coming from within an infected plant. What you are seeing (the white powderey looking substance) on the leaves is the flowering body of the fungus- the hyphae live within the plant. By the time you can visually identify the problem it's already well established within the plant. No external treatment (like sulphur) can fix the problem.

    PM proliferates in shaded and low-light areas of gardens where the humidity is raised; obviously countering these grow room conditions will slow the spread but it won't truly eliminate the fugus from the plants.

    The same is true for sulphur applications; be it from a sulphur burner or from a solution such as Safer's Defender. Sulphur will prevent the growth of PM where it is present on the leaf, but the PM still exists within the plant.... not to mention sulphur applications negatively affect the taste of the final product; it seems to concentrate on the resins and an experienced or trained palate will always be able to tell if there was sulphur applied to the plants from how the hash smokes. I don't recommend using sulphur on vegging for flower or flowering plants

    There is a product called Meltatox that is designed for application on ornamentals which gets into the plant and actually kills the PM. You should not spray this on plants that are going to be put into flower, or are in flowering. However, IMO it can safely be used to treat your veg state plants to eliminate the PM from your stock. I would suggest waiting at least 4 weeks before taking clones to be put into a veg/flower cycle.

    Of course the MSDS is available online and anyone considering using the product should completely read the label instructions to inform themselves about the factors involved, how to properly spray and what precautions to take, the product half-life, etc before considering using.

    It does work IME, and can be used as a part of a integrated approach that not only deals with eliminating all traces of spores from the growroom, but also removing the fungus from the plants themselves. Having either infected plants OR a spore infected growroom will ensure the problem persists as one will infect the other.

    I would remove the plants, clean the room with industrial greenhouse cleaner, and use a sulphur burner before putting the plants back in the room. Then separately cut back the mothers and sterilize with Meltatox. If the plants are for consumption I'd then wait a month before getting back on schedule to take clones and veg out for the next crop... any remaining Meltatox in the plants would be negligible.

    This product is not for everyone and is not safe to spray on flowering plants for consumption. I only recommend it's use to those that will use it responsibly and make themselves aware of the MSDS information available before choosing to use it.

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    I couldn't find your previous post on PM when the sticky went up recently, thanks for posting this Chimera.

    Feel free to ignore off topic, but do you have any similar info/tips on the types of mold that commonly affect cannabis (are they commonly pythium and botyritis?)?


      Wow thanks Chimera!

      I ve recently had issues with PM.... Its very sucky stuff

      I got a question tho.... If Pm is whithin the plant, does that mean different plants have differnt pm? I ask cause ive noticed PM looks different on different plants.... Some spread in little circles... some blotches... some u cant even see unless the leaf is on an angle! And lets say i have a plant that is much much more suseptible to PM, and another plant right next to it that doesnt have PM. Is the constant exposure infecting the less suseptible plant from the inside out... ? So the Pm doesnt just spread on the leaves?

      Also since ur a genius... If i'm growing a plant that seems to just be a PM magnet... (Like my current black domina)...Is it possible that the MSDS doesnt work?

      thanks for the info... i will prolly try this stuff as i have tried all other things...
      Have u tried using AN Pirahna?
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        Thanks for the info Chimera, always a pleasure.

        So once a plant is infected on the inside what makes it form on the leaf and create more spores? Does it think winter's over perhaps? When reading about PM online they always talk about it overwintering, are they talking about the hyphae? Whenever I would search systemic and powder mildew all that came up was the mention of different systemic fungicides; I don't think I would have ever known it was systemic without you sharing it. Thanks.


          Chimera - sorry to say that you are 100% wrong and as I can see from the responses above, you are passing your miss-information off to others as fact. Not good for you to do that. PM is distributed via spores. Spores by the millions. PM is a pathogen that feeds off the leaf tissue, and in rare cases the stems of plants. Infection never comes from within the plant itself, especially in the plants that are discussed here, since these plants live then die (they are Annuals, mildew can overwinter in Perennials under the bark or in the buds as hardened spores). Then you plant new plants. If it seems you have a continual problem, then your grow room needs climate modification or mother plant has an infection that you are not eradicating, or the new plants you have acquired are already infected with spores that are awaiting the perfect conditions to transform. Maybe you should dip your plants with water and spreader before moving to your grow room.The only part of mildew that actually grows in the plant is the "foot" of conidia. It is THAT foot, that attaches the leaf or plant. I farmed grapes for many years. Mildew is THE biggest problem in grape growing. In the 1960's and 70's, we had only sulfur to combat mildew, and sulfur only works with good coverage and high Temperatures, over 90 to 92 degrees. At those temps sulfur fumes and kills the infection. Below that, it is usually the water that kills the spores. That is why it is important, if you foliar feed, to cover 100% of your leaf surface, top and bottom and to use a good spreader. That way, the water, when it comes into contact with spores will kill the spores. Poor coverage will only raise humidity levels on some plant tissue making it an attractive place for a spore to infect your plant.

          There are hi tech materials that you may be able to find. I use several products myself when there is a problem. Sterol Inhibitors, which are safe on Tomatoes is a good place to look. Product names such as Bayleton, Rally and Elite. These types of products prevent the "foot" of the pathogen from setting roots into your leaves. Other new products available to registered farmers interupt the growing cycle of the pathogen and therefore kills it in that manner.I am not an organic grower. Been there done with that. My knowledge of this topic comes from the school of hard knocks and university curriculum over decades.
          Please do not miss-inform others with non factual garbage.
          Please see the links below.

          Pure Organics

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            Hmm, I'm just a dummy here to learn from the Cornell Plant Clinic:

            Disease cycle

            The fungi which cause powdery mildew are spread by spores produced in the white patches. These spores are blown in the wind to other parts of the plant or to other plants during the growing season. Generally each species of fungus will be limited in the number of plant species that can be attacked. For example the species of fungus infecting lilacs will not cause powdery mildew on apples.

            During the winter the fungus survives on infected plant parts and in debris such as fallen leaves. It may produce resting structures known as cleistothecia, which resist harsh winter conditions. These will appear as small black dots within the white powdery patches (Fig. 2). The next spring, sexual spores (ascospores) are released from the cleistothecia, shot up into the air, and carried by air currents to leaves of plants where new infections will begin. During the growing season, the fungus produces asexual spores (conidia) that help the fungus to spread and infection to build. This is the general cycle for most powdery mildews of outdoor plants. With houseplants the overwintering stage is of little significance. Depending on the environmental conditions indoors, the fungus could continue to grow and spread during the entire year.
            They also say:
            For indoor plants, disease management includes gathering up and destroying fallen leaves, reducing relative humidity around plants, and spraying with a fungicide. In New York State, some products that may be used to treat powdery mildew on indoor plants include: potassium bicarbonate (Greencure), Bacillus subtilis (Serenade Garden RTU* or Plant Guardian Biofungicide), and some products containing the active ingredient neem oil....
            For outdoor ornamental plants, gather up fallen leaves in autumn and destroy them. Where powdery mildew is a problem, resistant varieties (if available) should be grown. If needed during the growing season, begin fungicide applications when the first white patches are noticed. Repeat as indicated on the product label during cool humid weather. Some products with a broad range of applications for outdoor ornamentals include products containing: Bacillus subtilis, neem oil, potassium bicarbonate, sulfur or lime sulfur.
            I've been thinking of getting some of that Greencure potassium bicarbonate solution (mainly to spray on the top layer of soil in the pots), anyone have experience with that?


              Bumble and Wayzer,

              As a fellow grower of course I am happy to share my experiences with you; no thanks are necessary. Like any grower I have had to deal with these issues, and all I wish to do is share the knowledge I have acquired in dealing with them... as it may have been gained through a different route than others have taken. Some will learn from it some will debate it...

              Wayz - MSDS stands for Material Safety Data Sheet... every chemical product that travels must be shipped with a MSDS; this way whomever is handling the chemical (from delivery courier to lab scientist) can get access about how the chemical behaves in case of a spill etc so they can figure out how to handle it properly.... many are online just search and check it out. I used to work in a genetics lab so I know a little about these things, we had to take safety courses on potentially hazardous chemicals and how to transport them, etc.

              Greeninthethumbs I will try and touch on your points in my response to grapeman.

              grapeman- you may share a different perspective than I and that's great, but please show some decorum in here and adjust your attitude a little so we can actually have a decent dialog, and you are then more than welcome to participate.

              I was mistaken in how I phrased the statement, but am certainly not "%100 wrong" as you assert. However, I do need to contextualize that my above post was a response to a question posed at another site, and I should have slightly altered it for it to be suitable as a stand alone post... but was in a hurry and just copied and pasted it. You'll have to track down the original discussion (don't post it here...) if you want to keep up the attitude, so can get some perspective on my post. The mistake was surely mine, however, for posting it as I did above and not specifying that it was a quote I made in another discussion.... but not because the information within was inaccurate; it wasn't.


              When I say that PM "comes from within the plant" it was in context to the other thread where folks were seeing PM perpetually. I actually meant that part of the life cycle of powdery mildew takes place within the plant... and once a plant is infected, it will remain present for the length of the plant's life or until it is killed.

              Talk about "over-wintering" and "annuals" is is irrelevant- in this discussion we are obviously talking about cannabis plants and the fact that we are keeping selected individuals alive well beyond their naturally intended life cycle; ie mother plants. Cannabis ain't Vitis vinifera.... try "over-wintering" cannabis anywhere below Zero Celcius / 32 Fahrenheit and tell me otherwise. While we can gain perspective by discussing grapevine, it is not really relevant to a discussion of cannabis 'mother' plants being maintained indefinitely by artificial light cycles (ie 18+).

              Powdery mildew is OBVIOUSLY spread to non-infected plants via spores. This is no revelation to anyone other than those just hearing the words powdery mildew for the first time. My point in that post was intended to be that the "white powdery" part we see growing is the reproductive structure of a 'sexually mature' life stage of the fungus. (I say sexually mature to emphasize the reproductive life cycle element, but as people who understand the biology of fungal reproduction know it's not really 'sexual' per se, because the spores are generated only from a single individual, not two (male and female-pollen:ovule) situation.)

              The following information is based on all the research I've done on PM which is quite a lot, and my own personal observations after using all of the aforementioned products (including water!).

              Water is simply not as effective as killing PM spores as a potassium bicarbonate solution, look into the scientific literature... this is simple information to find on the internet. However, once a plant is infected by powdery mildew- no solution I've tried- not water, sulphur (sulfur), potassium bicarbonate.... nothing is as effective as sterilization of mother plants with Meltatox.

              Sulphur, to my understanding, inhibits growth of PM because the PM cannot easily grow where it is present. Many metals will also inhibit PM growth in areas where they are sprayed. However, other stages of the life cycle can continue to live within the plant in leaves, stems etc. Sulphur will not eliminate the PM in parts of the plant where it is not sprayed... neither will products such as Greencure that contain potassium bicarbonate (KHCO3).

              I've used them all on infected plants, and the PM keeps growing and comes back. KHCO3 will kill spores, but will certainly not eliminate PM completely from an infected plant. I do buy potassium bicarbonate in 50 Kg bags to spray around the property and especially near the well filtered intake vents; the filters and in place to reduce the amount of spores that can get into the rooms. Greenhouses are sprayed with commercial greenhouse disinfectants and then a concentrated solution of potassium bicarbonate (KHCO3). Prevention is obviously the cure, but I am speaking about infected plants with regard to the Meltatox. Continually spraying the plants to kill spores is impractical for my large gardens, and ineffective for mothers.

              On Sulphur: I don't like the taste of matches in my hash, which is made from every crop... you might say I'm a resin junkie. I realize Sulphur is used in grapvine/grape production and am fully aware of acceptable limits in wine etc. I know people use it with burners and I even have one myself.... but I taste it in the hash and buds, so I don't use it period. Some people don't notice the taste, but I do .... my palate is a pretty strong point I can smell and taste a lot of things many people can't. Maybe that's why I'm such a pot snob / hash snob (coinnoiseur/ cannoisseur?) but it certainly helps in selections.

              There is some evidence that potassium silicate strengthens cell walls and makes plants less susceptible to PM. It's not a significant enough affect to say that it stops PM... regardless I use it as pH up.

              Some plants are more susceptible to PM than others, and it probably has something to do with the specific genetics of the plants. There are research groups trying to identify QTLs for PM resistance/ susceptibility in various plant species, but as of the last time I looked into it in the literature there wasn't much going on as far as understand the cellular biology of PM resistance.

              I hope that clarifies somewhat...

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                What sulfur and potassium bicarbonate products are doing is changing (lowering or raising) the ph of the leaves, which is what pm doesn't like.
                Last edited by dongle69; 07-18-2009, 07:26. Reason: brain fart had to make a punk bitch happy


                  No dongle you are mistaken, scientific studies have shown the bicarbonate ion (which develops in the water when the KHCO3 dissociates) actually kills powdery mildew spores... I've seen the electron micrographs that prove it.

                  Sulphur inhibits the growth on a cellular level by interfering with biological processes opf the fungus this is also well documented on the scientific literature.

                  A higher pH spray does help to slow the fungal growth, but this is not the reason sulphur and potassium bicarbonate are used to combat PM.

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                    dongle 69 - "That is not what the manufacturers of these products tell me."

                    As a scientist, I tend not to trust salesmen.
                    However, we all must set our own acceptable levels of credibility when it comes to who and what we believe.

                    I go and do the research myself, some listen to manufacturers with financial incentives.

                    You make your own choice.


                    edit- hey dongle I don't know why you felt it necessary to leave a negative comment in the edit message above... "Last edited by dongle69; Today at 07:26 AM.. Reason: brain fart had to make a punk bitch happy"..... but it's unnecessary and definitely not appreciated that you leave insults for folks (myself, or any other participant) just because you had your ass handed to you in a debate. in the future please show respect to your fellow posters in this forum.... or you can restrict your participation to other forums. If you want to contribute and be respectful to all other members we are happy to have you and your intelligent contributions here, but we certainly don't need the attitude.
                    Last edited by Chimera; 07-18-2009, 14:51. Reason: added the quote that was deleted from the previous post for context.
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                      Originally posted by Chimera View Post
                      As a scientist, I tend not to trust salesmen. However, we all must set own acceptable levels of credibility when it comes to who and what we believe.

                      I go and do the research myself, some listen to manufacturers with financial incentives.

                      You make your own choice.

                      Below is a link to all of my grow reviews...there are a bunch so get off the clones, dive in, and find some new genetics to appreciate!

                      Click here for a link to all of my grows


                        So what makes the hyphae produce the white powdery spores? I suppose technically my Calizahr mom has been infected for about 4 years now but I go months and months sometimes without seeing a spot of white. Are these lil buggers always in my plant trying to produce spores and most of the time the environment is too inhospitable for this to occur? Are my plants constantly forming spore patches that are too small for the naked eye to see? I usually burn sulfur once or twice a month and that's about it...Sucks cuz recently I saw a few spots on a flowered calizahr where the stake was resting against a leaf and obviously the airflow was piss poor there. Now I saw a few spots on my c-plus cuttings that hadn't even rooted yet...I guess I'm fucked and all my c-plus babies are permanently infected? Never thought I'd say it but thank god my pallet's too shitty to notice the sulfur taste heheheh.

                        How prevalent are these hyphae? When you see a tiny spot on a lower leaf does that mean the entire plant is infected everywhere even if it's a 4 foot monster? Is there much research on I said when i searched pm and systemic i never found a single article that even said pm was systemic (not that i'm doubting you) but i wasn't searching for the cannabis specific species of pm. If you go months and months without seeing pm have you maybe taken clones off an area of the mom where hyphae weren't present?

                        And a word of advice on sulfur burners...when you first get them watch them, mine was literally a burner as the sulfur plate was set too low to the heating element and it ignited the sulfur. Didn't know this until i ran it in my drying room where a smoke detector went off. I run down there and see blue flames shooting out of the top and pretty much shit my pants. I was wondering why it practically killed my plants (not just the pm, sniff sniff poor mental floss could barely handle it) so i just raised the sulfur container. Now it just vaporizes. Anyway, great thread folks.


                          thanks for the info chimera.....have you experimented with copper products?... like this

                          In your opinion what is the best product for treating outdoor plants thr/ harvest that are infected?

                          3rd I’s Project---3rd I's F-13 & Vanilluna---3rd I's Outdoor 09'


                            Grapeman have you used Meltatox?

                            Listen dude, you can feel free to start a PM thread in the infirmary, your forum if you have one, or any other forum you wish but I posted this to share with folks how I deal with PM. I get lots of folks asking how to deal with problems like this.. and this thread is for them; not you. If you don't like it that's too bad.... don't feel obliged to post here. You obviously have your way of dealing with things and that's great- I'm glad it works for you. Your methods don't work on a large scale. This isn't debatable.... I've tried your methods and they don't work on the scale I grow in. Then I tried Meltatox and bingo the problem went away- and hasn't come back... same garden, same environment... identical conditions.

                            Advising people to get rid of PM with water is just silly..... it doesn't work. It certainly is not even remotely effective as potassium bicarbonate (KHCO3). This is supported by numerous articles in the scientific literature.

                            Spores are the most resilient life stage from any type of species on the planet, only the use of an autoclave at high temperatures and pressures will kill the toughest of them.

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                              Thank you for stating your knowledge to help us out.I stated what you are saying in this thread(and the other thread)and even quoted you.I was still told that I was wrong and that I should show one scientific study showing that pm is a systematic problem which can be passes through cuts of an infected mother plant...Ive also had no luck in finding Meltatox...