Oh no Judy! I googled it and here is the link. https://www.gardeningknowhow.com/houseplants/african-violet/powdery-mildew-on-african-violets.htm

Interestingly it also said sulfur isn't effective unless you use it BEFORE the PM shows. Well then I guess that is used as a preventative????

Also said a good cure would be baking soda and water spray.

Try this link (among others) and see how you interpret the info. I would hold off buying an air filter. I thik this can be fixed by some of the suggestions offered at the website.

Here is what I googled: what causes powdery mildew on african violets

Good Luck! Rosie

Thanks Rosie. I've tried all or at least most of the recommended cures for powdery mildew. It's definitely better since I have 2 room air circulators going 24/7, but it sill comes back on a few plants - always on the older flowers. I saw a couple of posts in Facebook AV groups where folks say an air purifier has solved their problem. Intuitively, it would seem that if a purifier removes mold spores, as some advertise, it should take care of powdery mildew, no? I would like to eliminate the cause, rather than treat the symptoms if that's possible. That's why I wanted to know if anyone here has tried one.

I don't know how true it can be, but I have heard that some plants are just prone to it? Not sure I buy that but some have said it!

Ok here is what I am wondering. For instance,,,,,run a fan. Ok, but do you have it at the right angle? Maybe the air movement isn't quite hitting a spot and that is where your mildew is?

Space between the violets,,,,,maybe you THINK you have enough space between them but for your conditions maybe you need a little more? I guess I am trying to say tweak your conditions and see if that makes a difference.

I just don't think buying purifiers etc. is the answer. I would try to redo my conditions first.
OR just move things around a bit. I dunno,,,,,sometimes it just helps!! Rosie

Judy, I posted a youtube link a few days ago that's basically about controlling thrips, but at 18:33 she also talks about powdery mildew. Worth a try?

https://www.youtube.com/watch?v=UTsSG0vsRcA&list=PLTvftXyXOsNQ1_d7WyhDP8mp5uhwwIHI5&index=1&t=99s

Joan

Thanks for the tip. The leaf shine suggestion is interesting. My problem is that the powdery mildew appears only on my flowers, and never on the leaves, at least so far. Would have to test whether leaf shine affects the flowers. Something tells me it would.

Yes, Judy. Probably worth a test. Did you view the whole video? I know it's longer than most people might like to watch. (Can't tell you how many times I've tried knitting videos when I've thought, "Just get to the point!") But early on, well before the 18:33 mark, she talks about how extremely light her application is. Plus, she has been doing it for thrips *while blossoms are present.* And later shots show no ill effects on the blossoms.

To me this suggests not only that maybe her kind of thrips aren't the same as what we face elsewhere in the world, because they don't seem to hide in flowers but go for the leaves; but also that possibly the leaf shine she uses isn't hurting her blossoms, when applied as lightly as she does. So look through the whole video, because there are places where she demonstrates exactly how many squirts she may do, and what the droplets look like as they settle over the plant.

Here's one more observation, but from outside the leaf-shine/AV world:

I have quite a number of ninebark shrubs in my yard, which I cherish for their purple foliage. Unfortunately, ninebarks are very susceptible to powdery mildew, when temperatures and humidity levels get high as they often do, here. I lost two shrubs, nearly lost another, and have five remaining that I've had to work hard to protect.

My most effective protection measure has been to remove noticeably infected stems, with their foliage (edit: in late winter), and spray with horticultural oil soon after, if not immediately. It's best to do a thorough spraying in late winter/early spring, with the "dormant" formulation (stronger). At that time of the year I remove anything I observe that has been infected, including fallen leaves/debris. I prune away "bad" stems at the same time as doing late-winter pruning for rejuvenation, airing, and shaping. Then I spray with whatever is the appropriate concentration of horticultural oil, given the state of dormancy/bud-break/leaf-out. I can't say I've had 100% elimination of powdery mildew because those spores will always be around, but for sure I've been able to knock it down, and it's not killing my shrubs anymore.

The primary active ingredient in Bonide "All Seasons Horticultural and Dormant Spray Oil" is mineral oil: 98%. Listed pests and diseases include various mites, thrips, and powdery mildew.

So I think there's hope.

Joan

Woo hoo! Looking forward to your report! :D

Well, I received both the Bonide Spray oil and the leaf shine and here's my report. I first tried the spray oil on one of my orchids that clearly has an infestation of spider mites - fairly common in phalenopsis. It is a very heavy oily substance that I wouldn't dare try on an AV. I'm sure it would kill it in no time. So that's it for that one. At least I have several orchids I can use it on if necessary.

I then tried the leaf shine on one of my 2 plants of Mac's Basic Black with Pearls. It's one of my favorites, but for some reason it's a powdery mildew magnet. It was a much lighter substance, and let's just say the plant is still alive and the leaves look fine. However, the flowers shriveled up within a few hours. And as my powdery mildew problem manifests mostly on the flowers for some reason, this one is out too.

As I would really like a solution for powdery mildew that doesn't involve constant spraying, and as my plants are all separated by at least a couple of inches and I have 2 air circulators going 24/7, I wondered if anyone had any experience with an air purifier. Since a few people on Facebook claim to have had success eliminating powdery mildew with a purifier, I'm going to bite the bullet and get one that is highly rated and large enough for my plant room. Even if it doesn't work, it should help with allergies, etc. Wish me luck!

Judy, thank you so much for biting the bullet and trying these products! You're a hero.

I'm not surprised you couldn't dilute the Bonide hort oil enough. I wouldn't have suggested it for AVs - just meant to point out that it's the mineral oil in it that seems to be what's effective for pest and disease suppression, and it's the mineral oil in "leaf shine" that Dani, in the video, was suggesting was effective re powdery mildew. I reserve hort oil for outdoor applications, and for use, in very dilute form, before bringing woody but not-hardy perennials in for the winter.

I've so very sorry about your Basic Black with Pearls. I've seen that one - pretty precious!

Air purifier is an interesting idea.

Question: how humid is it at your place? Could a de-humidifier be of use, both for the plants and possibly for your own comfort? Not that it's any more economic. These units run the gamut of prices, just like an air purifier.

Well, sigh. Sorry I couldn't be of more help.

No worries about Basic Black. The plant is still fine and has new buds, plus I have another one that's fine.

I didn't even try to dilute the Bonide oil. I comes ready to use. But as the much lighter leaf shine destroyed the flowers, I wouldn't even try to use a diluted Bonide oil.

Re my humidity level, it never goes much above 50%. Also, I don't think high humidity necessarily causes or exacerbates powdery mildew. I've found it to appear in all seasons, including especially when the heat first comes on for the winter.

In any event, it's not a terrible problem for me - just an occasional annoyance. Thanks for all your thoughts.

You can also try spraying with strongly brewed chamomile tea.

Sprayed a couple today with Immunox. They're doing fine and no damage to the flowers.

• Cool. I looked up the active ingredient in it, myclobutanil, and it seems fairly safe especially for ornamentals. I'd think twice about using it on fruits/veg. Several US states and Canada ban its use in medical marijuana production because it breaks down into various heavy metals when heated. Nothing is said about fruits and veg, but still... Anyway, congratulations!
• Joan
• I have no idea why this is coming out bulleted! Uff da.

Guys - I found an old recipe - add 1/2 of a table spoon of superphosphate per gallon of the soil. Superphosphate is very slow to dissipate, so it won't burn the roots... Probably better to try to reduce the size of the granules anyway..

Supposedly when the AVs have enough phosphorus - they fight the PM better.

I am going to try...

Interesting Irina. 2 questions - do you mean gallon of soil or gallon of water? Also, what is a Superphosphate and where would you get it? Thanks.

Judy

IRINA!!!!!!!!!!!!!!!!!! WELCOME BACK!!!!!!!!!!! I knew you would be back!!!! Rosie

Morning Judy -

in a gallon of soil.

Superphosphate is a fertilizer for outside plants. People who grow Irises usually buy them - because they sprinkle them every fall and add into the soil when planting. My understanding that outside plants with overwintering root structures - rhizomes, bulbs etc. like extra phosphorus.

Regarding the soil mix for AVs I am thinking that Bone Meal is a possible option. Bone meal is about 15% phosphorus, very slow release. Regular Superphosphate - 20% , Triple Bonide Superphospate - 48%. you can get 4 pounder of it on Amazon. I presume that the original recommendation was about a regular 20%. So =if you got the triple S.P. - decrease the dose... 3 times.

I am thinking something like 2 teaspoons of Bone Meal will do the trick - and you can get it in good garden centers.

And do not forget to give some to irises, tulips and lilies.

Rosie, your warm joy at hearing Irina totally made me smile! And yes, welcome back, Irina! So very good to hear you again!

I very VERY much agree with Irina that a healthy plant is going to be better able to fight off a variety of diseases that may always be opportunistic.

Just curious, Judy: what do you use for your regular fertilizer? The Optimara formula? Because that's somewhat lower in P: 14-12-14

Personally, I think bone meal is wonderful stuff in the right places. I've had nearly unbelievable success with some amaryllis bulbs I repotted last winter - scrawny things - which tripled (I'd say quadrupled if it weren't just too fabulous to claim) in volume over the summer. Bless their exuberant hearts. But if Optimara's very well respected 14-12-14 formula is what you want, and you go throw some bone meal or superphosphate in, that's going to change what you're feeding your violets.

I'm not disagreeing at all, mind you! No no. Just that, if this is what one needs - maybe something similar can be achieved, and perhaps more quickly, by using a different fertilizer formula?

Joan