Are there any easy solutions for powdery mildew?

Do you have any easy, effective solutions to powdery mildew? I'd love to just spray some solution of something on the leaves, but since moisture is part of the problem, that seems counter productive. I've got it on beans, tomatoes, and cukes. Arghhh!

Dusting with sulfur is recommended, but its action is more preventative than remedial.

Diluted milk is used as a spray, and the active principle here would be to stimulate naturally occurring lactic acid bacteria on the leaves. Thinking more broadly, if you can get the right bacterial compost tea on the leaves, perhaps they can outcompete the mildew and keep it under control. The big question there is how to get the right mix of bacteria, and can you do better than a dilute milk spray. You could try adding a puree of healthy plant leaves to an aerating compost tea and hope that the bacteria from the healthy leaves is multiplying and see if that works.

I plan on trying the raw milk myself. I let it sour some, try it and let you know how it works. I have heard though that its not a cure all, it just slows it down enough to keep the plants going.

Thanks for the ideas. I've read about some other ones too, but I'm wondering if anyone has had any proven success with any of these concoctions?

Often times your plants will have powdery mildew but continue to do fine. Yes, it tells you something isnt optimal with your plants. But it doesnt sceam go grab the poison. On that note, what's with all the new faces showing up looking for advice on what to spray what to spray? Start with healthy soil, vigorous plants. Amazing how all your problems disappear. In time. Drive slow, homie.

Adam Klaus wrote:Often times your plants will have powdery mildew but continue to do fine. Yes, it tells you something isnt optimal with your plants. But it doesnt sceam go grab the poison. On that note, what's with all the new faces showing up looking for advice on what to spray what to spray? Start with healthy soil, vigorous plants. Amazing how all your problems disappear. In time. Drive slow, homie.

I wasn't looking for poison advice. I was hoping for something like baking soda and water. I had healthy plants, but then got powdery mildew. And the leaves seem to be getting covered and dying about as fast as new ones grow, so the plants are kind of treading water. I wasn't expecting a solution, but was hoping nonetheless.

I'm not sure but I would think active cultured yogurt might be more effective if you're looking to add live bacteria. I've not had any PM yet but intend to try yogurt mixed with water in a sprayer if I end up with it. It always shows up at the end of the season to claim the last pumpkins before the frost.

As a side note: I try to plant squash and cucumbers every two weeks through the season so that I always have good young plants going. Once they show signs of stress, I just pull them out and plant something else. I'm finding this strategy to be more effective at keeping the harvest going steady and keeping pest issues down. Also, try planting them in different areas so that the PM doesn't easily spread from one plant to the next. Rain and irrigation that hit infected leaves, spreads the spores around as well.

As you go along, your soil will improve and these things will be less common. Don't get discouraged. We all have our challenges. Just have to keep plugging along. I just found one of my new cherry trees, dried up and rotted to the root. Thankfully I planted more than one.

Best of luck

I find plants that are in soil with heaps of compost/organic matter, and really, really deep mulch suffer way less fro pm.
From what I understand, pm spores are everywhere, but it usually only gets problematic when plants get water-stressed in later summer.
I've always heard about the water-on-leaves no-no, but it should be fine to spray earlier in the day. Just as long as the leaves don't stay wet overnight as that can encourage all sorts of problems.
Once plants have it actually visible, I've found remedies to be basically pointless: the only way I've dealt with it successfully is by piling on compost, maybe aged sheep manure and mulch and keeping the plant's roots moist.
Aside from moisture retention, this kind of thing gives the plants enough to nutrition so that they can keep ahead of the mildew.
As has been mentioned, succession planting works well for some things, but not so much the plants you've mentioned.

Hi Scott,

I'm interested that you say "moisture is part of the problem" - I wonder if you are under the misapprehension I used to believe which is that powdery mildew is caused by moisture? This seemed sense to me as the kind of mildew you get on eg old clothes is certainly due to damp. However (and shoot me down if I'm teaching you to suck eggs and have the wrong end of the stick), the powdery kind of mildew is caused by LACK of water at the roots, as Leila mentions above ("water stress"). I have known roses have powdery mildew one year then not get it the next as there was more rain to water the plants.

I realise I'm only pointing towards prevention but hope this helps.

Rosalind

yes its true, and counter intuitive, PM is caused by lack of moisture, dry spells. lack of sunlight also exasperates it.

yeah all you can do is keep it at bay, cut the plants down or at least the parts that have mildew, cut them back.

some people say jojoba oil works, others say colloidial silver works, but i dont know.

it's better and easier to just cut off the bad parts, or remove the plant.

or rather the issue with moisture is too much, then way too little, then too much.

but its more caused by dryness, which is weird and seems backwards.

Yes, that's it - I'm on heavy clay so we get waterlogged in winter and it dries out in summer (if we have a good summer, like this year). I have found that improving the humus in the soil helps in the long term, and of course watering in extremis. I often chuck a bucket of grey water on the roots of my big climbing roses - they tend to have dry roots as they're planted by the walls in order to climb up the house.

Hmmmm. Interesting comments on the wet soil / dry soil possibilities. I water regularly so I don't think that's the problem, but who knows. I had read that shade and humidity are a problem. I am on the coast, and it has been humid lately. Also, some of the plants are shaded part of the day. Now though, the powdery mildew seems to be spreading faster and getting on everything in the garden! I'm wondering about the rest of this season...
Seems it's more important to keep it from ever getting a toe hold, and once it sets in, it's only a matter of time.

PM is pretty evil! ah ok maybe not, and thats my projection, but it is tenacious.

and anywho it might sound odd, i know i thought the same too once, but it is dryness that causes PM, and what makes it come out in full flush. uneven watering especially- being too wet and then too dry.

it might not be that you're not watering enough, it could be compaction so water isnt getting deep, the kind of soil that isnt pourous, and like was said before you probably need more organic matter in your growing medium. you could also try cultivating the soil a bit, with a pitchfork or small shovel/rake, and just stir it up some.

once you have it, you have it in the plant. it invades the cells of the plant, and by the time you see actual PM on the leaves its far too late to do anything about it except keep it at bay, cut the plants back.
or discard the plant, cause it will spread. if you get it in a greenhouse its really bad, it will linger, but not be visible.

sometimes when you buy plant starts, the plants already have PM, but you cant see it.

even cutting back the plant and removing the parts with PM, which is how i tend to deal with it, doesnt totally work, it still has latent invisible PM potential....and if the same conditions (dry roots, uneven water/dryness periods, lack of sunlight) happen it will come back.

because it gets into the plants cells, supposedly even the seed that plant later produces will have PM, which can be kept at bay as long as the conditions are right...but if it starts getting too dry, not enough sunlight, then it will come out.

as for something to spray, if you want to try something, the word out here is jojoba oil. it (supposedly according to other people) coats the plants leaves, prevents it from spreading it spores, and suffocates it.
also many people swear by colloidal silver to get rid of powder mildew, but it is extremely expensive unless you make it yourself. i tend to doubt that it actually gets rid of the PM, but apparently people have used it successfully to at least keep it at bay.

heres some links, was just talking to google =)

this has some good ideas.
an excellent idea is to not grow plants that are susceptible, thats actually been my most successful attempt to avoid PM. i gave up on growing squash even, in the rainforest it's possible but very difficult to grow squash. or any other kinds of plants that are likely to get the funk, and not the good kind of funk!

a lot of *permacultury* plants -if i can call them that- are actually resistant to PM, they just dont get it.

unfortunately, this includes strawberrries, but i love growing tons of strawberries!
the wild/alpine/coastal strawberries , the tiny kind, are more resistant to PM, they dont get it at all or rarely. but those big juicy strawberry starts you can get, unfortunately have the PM potential...maybe even when you buy the plants from greenhouses that have PM.

the link:
http://www.ctahr.hawaii.edu/UHMG/FAQ/faq-powdery-mildew.asp

Problem

There are white, powdery spots on the leaves and flowers of your vegetables.
Description

Powdery mildew is a common disease on a wide variety of vegetables and ornamentals. It is caused by different fungi and is species specific, though the symptoms and method of control will be similar. Symptoms of powdery mildew include white, powdery spots on both surfaces of the leaves which may spread to stems and flowers, and occasionally, to fruit. On tomatoes, onions, peppers and artichokes, you may see yellow patches rather than powdery growth. Leaves may turn yellow, die, and fall off of the plant. There may also be some distortion of leaves. Plants in the cucurbit family are especially susceptible (cucumber, melons, squash, and pumpkins.)
Information

Powdery Mildew on Vegetables (University of California, IPM On-line)

Control

Plant disease-resistant varieties. Plant in full sun, with good air circulation, and use slow release fertilizer so that you don’t over fertilize your vegetables. Fungicides will help, but must be used at the first sign of infection. See an extension agent about the use of fungicide or consult the UC Davis IPM publication listed above.

You can also use neem oil, jojoba oil, wetable sulfur or horticultural oil to treat powdery mildew. Do not apply oils when temperatures are above 90 deg.F or within two weeks of spraying plants with wetable sulfur. Sulfur products work best when applied before symptoms appear or at the first signs of disease. Read and follow product labels carefully. Reapply every 7-10 days until all symptoms are gone.

Kendal Lyon, Hawaii Island Master Gardeners

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another one:

http://urbangardenmagazine.com/2009/08/how-to-beat-powdery-mildew-in-hydroponics/

I was surprised at how much of what I consider 'misinformation' re pm is on the net. Naiive, I know!
I must have got most of my info from books, as consistent soil moisture and high fertility to combat pm seems to be kind of ignored online.

this fact sheet is kind of helpful

Potassium bicarbonate is the most effective solution to PM that I've found to date, definitely more effective and less phytotoxic then baking soda (sodium bicarbonate) and as an added bonus the potassium is absorbed as a foliar fertilizer. Food safe and naturally occuring, it's not as sustainable as bacterial preventative measures, but if it's between significant crop loss and using a potassium bicarbonate spray, I'd have no problem using it in a pinch.

You can check out "greencure's" website to learn more, http://www.greencure.net/what_is_greencure.asp, I just bought pure potassium bicarbonate locally though and used a good quality wetting agent.

leila hamaya wrote:PM is pretty evil! ah ok maybe not, and thats my projection, but it is tenacious.

once you have it, you have it in the plant. it invades the cells of the plant, and by the time you see actual PM on the leaves its far too late to do anything about it except keep it at bay, cut the plants back.
or discard the plant, cause it will spread.

I agree it is EVIL!
I hadn't heard about it being "in" the plant. I thought it was mold that grew on the leaves, and then the spores float in the air from leaf to leaf?

Scott Burns wrote:I agree it is EVIL!
I hadn't heard about it being "in" the plant. I thought it was mold that grew on the leaves, and then the spores float in the air from leaf to leaf?

Nope, powdery mildew covers a number of systemic fungi that infect plants when weakened through stress. What you're seeing on the leaves is the bloom of spores as it spreads, kinda like how mushrooms are the fruiting body of mycelium, not the main body itself. That's not to say that once infected a plant will always show powdery mildew, if the plants healthy and unstressed you probably won't see any signs although growth will still be affected. Once it get stressed though it'll pop out again in abundance. So depending on how valuable the plant is it's a tough call to treat or remove the infected plant.

Leila Rich wrote:I was surprised at how much of what I consider 'misinformation' re pm is on the net. Naiive, I know!
I must have got most of my info from books, as consistent soil moisture and high fertility to combat pm seems to be kind of ignored online.

this fact sheet is kind of helpful

Thanks for your fact sheet link! I highly recommend everyone read it. I learned a lot from it.
One thing was this:
"Powdery mildews produce mycelium (fungal threads) that grow only on the surface of the plant. They never invade the tissues themselves. The fungi feed by sending haustoria, or root-like structures, into the epidermal (top) cells of the plant. The fungi overwinter on plant debris as cleistothecia or mycelium. In the spring, the cleistothecia produce spores that are moved to susceptible host tissue by splashing raindrops, wind or insects."

Scott Burns wrote:

Leila Rich wrote:I was surprised at how much of what I consider 'misinformation' re pm is on the net. Naiive, I know!
I must have got most of my info from books, as consistent soil moisture and high fertility to combat pm seems to be kind of ignored online.

this fact sheet is kind of helpful

Thanks for your fact sheet link! I highly recommend everyone read it. I learned a lot from it.
One thing was this:
"Powdery mildews produce mycelium (fungal threads) that grow only on the surface of the plant. They never invade the tissues themselves. The fungi feed by sending haustoria, or root-like structures, into the epidermal (top) cells of the plant. The fungi overwinter on plant debris as cleistothecia or mycelium. In the spring, the cleistothecia produce spores that are moved to susceptible host tissue by splashing raindrops, wind or insects."

yes that was a good read, i agree with most of it , but personally disagree with that statement. in my understanding it is systemic and invades the cells of the plant. there are also several different kinds of PM, so maybe some of them act slightly differently, but they all look the same.

i also disagree that it implies cultivars are more resistant to PM...although some plants are more or less susceptible to it and i am sure there are some good cultivars that are resistant. i tend to see that wild plants, pioneer plants, plants that are closest to the grandmother version of that species, heirlooms, not messed with as much by "conventional" agriculture, as being much more resistant.

fussy annual cultivars, especially when they are grown in places that arent their ideal conditions, tend to be much more susceptible to it, IMO. also plants can get weaker and weaker by being reproduced by cloning, this is one of the diseases that happens commonly after a plant has been cloned multiple times, like some clone only strains. if the parent plant has it, the cuttings will also have it, and even when it doesnt show- its still in the plant.

and that it is caused by dryness, uneven watering, lack of sunlight. if theres no water at the roots, the leaves and top of the plant start pulling in moisture from the air through the leaves instead of the roots. well might be not exactly accurate to say this causes it, but its one of the conditions that exasperates it, allows it to flush and produce the mildew, but the PM is already inside the plant cells. so back to- uneven watering- too much moisture being pulled through the leaves and not enough water at the roots. but the leaf must be dry, conditions must be dry, for it to fruit, and come out in full flush on the leaf.

i'm sure theres a lot of ideas about exactly what is going on with PM, and its hard to know for sure what exactly is happening with the plants.
i grok it in a certain way, as it was explained to me and as experience has shown me. i cant say for sure i understand it completely, but this is my understanding, it quickly invades the entire plant and once it has PM, it will always have it inside the plant but wont come out until the conditions are right..

and not to save the seeds of that plant, though i have successfully harvested food from the plant after getting it under control, and the food was fine.

some people dont think it's systemic, but i do.

A preventive measure you can take is to make sure you have a good amount of micro-nutrients in your soil. Copper in particular. Foliar feedings can work as well for this.

Soaking horsetail (and other plants high in silica) in water for extended periods of time should give you a good extraction of silica/silicon. Dry the plant material. Chop as fine as possible. Use undiluted as a soil drench or foliar spray. Increasing levels of silica in your plants will aid in the strengthening of cellular membranes, giving PM a harder time to take hold. Good preventative measure. This site, http://www.usda.gov/fundinglapse.htm, though down due to the gov't shutdown, is a good resource for other plants high in silica/silicon. Diatomaceous Earth is 80-90% silica. Comfrey contains good amounts. Many rock dusts contain silica as well. Given how abundant this element is to the mother earth, it should be easier than not to source something locally.

Mulching with, and running horsetail/high silica plants through compost/vermicompost are also great/better ways to get this element into the soil/plant.

Pruning to increase air circulation, and sunlight penetration can make a huge difference. Sunlight sanitizes, and increased air flow will decrease the humidity that PM loves.

Thank you for posting this thread! We have a maple sapling from my Dad's woods that we planted last fall, and this summer in August it developed powdery mildew. The odd thing was, it is in a small garden in our front yard, in a sandy soil, with 3 inches or so of wood chip mulch on the bed.
We've had weird conditions this summer. Dry, then wet. Lots of rain and hot humidity in August. But our street is on a hill and seems to be a wind funnel, so I thought that mildew wouldn't ever occur in the windy front yard.
Having read this thread, I now think it was probably in the wood chips that we bought to mulch with. None of the other plants in the bed have been affected.
Weird.

Interesting. Paul Wheaton has a video on youtube wherein there is demonstrated a biodynamic solution. I am a little surprised no one has mentioned it.

If I were going to make compost tea (and I do use it regularly), I would use a fungal based, rather than bacterially based one, because I believe that PM is a fungal disease.
JOhn S
PDX OR

Peter Ellis wrote:Interesting. Paul Wheaton has a video on youtube wherein there is demonstrated a biodynamic solution. I am a little surprised no one has mentioned it.
http://www.youtube.com/watch?v=4KLt6R90VlQ

There's been some discussion about equisetum/silica, though maybe not in direct reference to biodynamics?

Equisetum/horsetail and its silica is one of the named remedies fro Rudolf Steiner and a crucial part of biodynamics.
John S
PDX OR

calcium deficiency / calcium availability is a common root cause of pm..

some one please help meeeeee powdery super bad and i have tryed every thing my food is going to waste and im loseing money cant afford a loss any bigger iv tryed all of the milks from soy to coconut i seen the milk thing on the fourm and figured id try all milks and still nothing i really hope this isnt a dead thread please atleast tell me im not alone here !!

Some have used a baking soda solution.
John S
PDX OR

I've been listening to podcasts from John Kempf of Advancing Eco Agriculture and his take is to produce healthy plants. Apparently the fungal spore releases an enzyme that breaks through the cell walls and begins the infection. If the plant has the right balance of nutrients, it can deposit lipids in the leaves and the lipids are impenetrable to the fungal enzymes. He applies the same logic to all pests in that they all have very particular digestive processes and healthy plants can produce enough secondary metabolites which make them indigestible to almost all pests. If you check out Dan Kittredge from Bionutrient Food Association, his take is that if you have fungus eating your plants, you're growing fungus food and not human food 🤣

I've had good success using raw milk diluted with water (40% milk, 60% water) and spraying all over foliage. Has to be done in the early morning or evening over a couple days and it should clear up.

Yes, many have used a milk solution. I think it needs to have sunshine on it for the chemical reaction to occur, if I recall correctly.
John S
PDX OR

I was told long ago that comfrey will get the powdery mildew and help exhaust it from the soil, and that it's fine to still chop and drop the comfrey even when it has mildew on the leaves. But now I am not sure I should be putting those spores back down on the garden. Suggestions? (Is my comfrey making my garden inhospitable for other food plants?)