you can try water misting to the point of run off regularly. PM is an oddball fungus in that it doesn't require wet surfaces to establish so arid conditions suit it fine. It tends to rupture if forced to absorb too much moisture.

You can likewise try the various organic methods such as adding milk and/or baking soda to the water.

Unfortunately once established it's often difficult to impossible to eradicate other than by removing the infected foliage and treating what's left to prevent infection.

Eggg gad to that vinegar it darn near kills everything
I won't be leaning to the milk idea to much but thats just me. baking soda is a yes from me even though it is myth at best mix 1-2 tablespoons to a gallon of water
good air is deffinatly key problem is it is very difficult to get this air inside during our cooler months
For PM control I am a K-neem fan organic it is although I don't know if that's a 100% safe idea for your cat
You alrady know this but just as a review
remove any infected leafage keep leaves as dry as possible
You can get away with a bowl if not use a kitty litter box type of box to hold enough water to cover the holes by an inch or so and wick water in a sence add some water to the top as well let it leak in to the bottom of box or bowl I set my inside growers in this box idea for 30/45 minute time frames

I do think K neem or even just neem may cause rash on kitty so plz plz double even triple read up on that and even ask the vet

Read the label on k-neem or neem for proper use and if you do go that way bring that bottle to the vet to let them decide if you should use it or bring it back for refunding

good news is baking soda wont hurt kitty. bad news it is myth but I too dismiss that and use it from time to time as an additional preventive measures

best news is Neem is highly effective for PM control worst news is it might hurt kitty I wish I knew for certain even then I'd warn yah

http://www.dirtworks.net/Neem-Oil-K+Neem.html

also avalible at most grocery stroes in a pre mix spay bottle at the cut and indoor flowers area

Try either a mixture of 1 teaspoon baking soda in 1 quart of water or a 50/50 mix of fat free mik and water both sprayed every 5 to 7 days to control the Powdery Mildew.

baking soda is a yes from me even though it is myth at best

It is no myth! Bicarbonates have been in use for a long time as fungicides and their effectiveness has been well studied and documented. Cornell University has been extremely active in researching this issue and has even given its name to the common baking soda fungicide recipe many organic gardeners use. This recipe is quite effective on powdery mildew especially. The bicarbonate has been found to disrupt the cell walls of the fungus as well as altering the surface pH, making it inhospitable for cell development.

The only 'myth' involved is that every Tom, Dick and Harriet that whips up this concoction thinks any similar combination, not to mention all sorts of custom additives, will be equally effective so zillions of recipes travel around by word of mouth, many of which may have limited effectiveness or be outright dangerous to the plants. First, potassium bicarbonate has been found to be 25-35% more effective than sodium bicarbonate, just a mix of baking soda and water has very limited effectiveness (incomplete coverage and washes off quickly) and adding dish soap may be counterproductive, as it often adds unnecessary chemicals and antibacterials and can cause phytotoxicity.

For a homemade version, use 1 tablespoon baking soda to a gallon of water. Add 2 teaspoons vegetable oil, insecticidal soap or neem oil and shake well to emulsify. The oil/soap/neem oil acts as a surfactant and will help the soda mix coat and adhere to the foliage. The original Cornell recipe used horticultural oil for this purpose but over the years that has been found to produce some unwanted side effects.

Wes, neem is not good for bees. It makes bees very sluggish and disoriented. If you use it it's best used when it's almost dark so that the bees won't get to it. Neem requires 4 hours' drying time.

Wes, even though milk is very ineffective on blackspot it will work on powdery mildew. Powdery Mildew is the one thing that milk is effective with.

Powdery mildew is temporarily cured by Greencure and the other bicarbonates that GardenGal mentions, but you have to keep applying it all the time. In my particular garden, the powdery mildew strain hates the fish foliar spray the most out of all that I've used. I'm not sure why this is. I think it's just the particular strain that I have in my garden.

The plant to be treated is indoors.....doesn't seem like many bees would be affected :-)

Milk is an equally effective organic fungicide. The lactic acid (alters pH), the antibacterial properties of lactobacill and the immune boosting potassium phosphate are what makes it effective in disease control. It has documented effectiveness against powdery mildew, botrytis, red thread in lawns and yes, black spot, but as a control, not a cure. But then most fungicides are prophylatic rather than curative in approach.

What is the plant potted in? If a good well draining container soil, PM can be kept to a minium, but you do need to keep any existing infection from spreading and that does require repetitive spraying. There really isn't any way around it.

There have been several discussions about using corn meal to control blight in tomato plants. You simply spread it on the ground, at the base of the plant. I have not used this method personally, but I would consider using it to control powdery mildew in catnip.

sorry, Gardengal but I was actually talking to Wes, not anyone else and just about my concerns with neem. I know he uses it a lot outdoors. So pardon my off-topic response. It had nothing to do with the catnip.

Another off-topic remark again, bicarbonates are far more effective than milk in controlling blackspot. Milk does minimal control. This has already been discussed prior at our organics rose forum. Anyway, enough off-topic responses for me. LOL! I am going to shut up and exit this thread so that valued responses can be given to BlackeyedGirl's Powdery Mildew.

In the case of Powdery Mildew I do! completely agree that milk is very effective against powdery mildew.

Has anybody tried milk's whey against PM?

Wow! Thank you guys to much! Many many many options here!!!

#1 I've been looking at getting some neem oil for quite a while as I also grow orchids and it is very effective for a lot of what ails them as well.

#2 Neem oil is generally regarded as pet safe. You can even use it as a wash to help rid your pet of fleas or a fungal infection. It cannot be used "straight" on cats & high concentrations can make them sick, but I predict a plant treated with it probably wouldn't hurt them. I back this up by saying I wash all the nip I give them before it gets to them so that should help remove excess residue. I have a good friend who makes her own horse fly spray using neem oil. I will try a few other mixes before goign this route tho.

THANK YOU for all the highly informative responses!!!

Unfortunately it is getting to cold (and it has been too wet) outside lately to move the plant back outside.

This is what I think I'm going to to:

#1 repot the plant. I think the pot it is in is too big, so it is taking too long to dry out. SO, I am going to move it to a smaller pot which should be easier to control the water on.

#2 start new seedlings in a different pot, far away from this one (just as back up). I am going to add perlite to the soil to help increase airflow & make sure the pot has increased drainage.

#3 Start treating the plant with chamomile tea or milk and move towards the baking soda formulations.

#4 remove badly infected portions.

#5 turn up the heat!

I will keep you all updated on how this goes!

Powdery Mildew is a fungal disease but the fungi that cause it is any of several depending on the plant. As a general rule to live and grow the spores need a fairly high relative humidity so if this started on the plants sometime after you brought them inside that may be an indication that your homes humidity levels is too high to be healthy for you too. It is not necessary to turn up the heat, but determining why the humidity is high and correcting that is the best solution.

Although it's been a good while since this thread was active, I thought I'd share some good answers that I've found:
(I forget where these came from.)

* Potassium bicarbonate: Similar to baking soda - but with potassium, rather than calcium - this has the unique advantage of actually eliminating powdery mildew once it’s there! But - again - calcium bicarbonate won't work! Potassium bicarbonate is a contact fungicide which kills the powdery mildew spores quickly. In addition, it’s approved for use in organic growing.

* Vinegar: The acetic acid of vinegar can control (Note: NOT eliminate) powdery mildew. A mixture of 2-3 tablespoons of common apple cider vinegar, containing 5% acetic acid mixed with a gallon of water does the job. However, too much vinegar can burn plants. On the other hand, sometimes a little stronger dilution will be necessary: Experiment; start weak, and increase strength only as necessary.

I've used this, with amazing success! I think I used a TEAspoon per QUART, but I can't find that documentation.

Wet every part of the plant well (it's a myth that powdery mildew prefers wet foliage). If the spray doesn't coat the leaves well (but just beads up), add a TINY amount of the PUREst soap you can find to the spray.

P., baking soda is sodium bicarbonate, not calcium bicarbonate (whatever that is). Sodium bicarbonate really does work.

I worry a little about your prescription for the vinegar. It's very important that the dosage be accurate or leaf tissue can be burned. I also think that a warning about the very real effect that 2 or 3 T. of vinegar/gal. of water can do to the soil pH if carelessly watered in on a routine basis is important.

I always cringe a little when someone recommends pure soap or real soap, but don't explain what that means. I suggest that anyone discussing a 'pure soap' be prepared to give examples, brand names. I assume that you mean a plant based liquid soap, free from fragrances and dyes?

My favorite home remedy for PM is 1 T. baking soda, 1 tsp. horticultural oil, 1 tsp. insecticidal soap, and 1 gallon of water.

Thank you, rhizo_1 (North AL) zone 7.

Let me respond point by point:

.

"P., baking soda is sodium bicarbonate, not calcium bicarbonate (whatever that is). Sodium bicarbonate really does work."

I meant sodium; I don't know how calcium got into my head!

.

"I worry a little about your prescription for the vinegar. It's very important that the dosage be accurate or leaf tissue can be burned. I also think that a warning about the very real effect that 2 or 3 T. of vinegar/gal. of water can do to the soil pH if carelessly watered in on a routine basis is important."

My precscription for the vinegar is clear (as opposed to blackeyedgurl's "diluted"), and has been tested (by me) on catnip. (Note: "Vinegar" means the 5% vinegar that's what one gets at a store.)

It's always the case that one may want to try even more-dilute mixtures first, especially on fragile or valuable plants.

And concerning your "carelessly watered in": To be clear, I wasn't talking about "watering in", just spraying the foliage (although some say that lightly spraying the surface of the soil can help with fungus gnats). Of course, when one sprays the foliage, there's always the issue of how much ends up in the soil. Optimally, none would - and I work to achieve that as much as possible - but lotsa times, that's unavoidable to some extent.

Note that this vinegar solution is so dilute that application such as the above shouldn't change the pH of any soil-based medium, absent extreme over-administration.

.

"I always cringe a little when someone recommends pure soap or real soap, but don't explain what that means. I suggest that anyone discussing a 'pure soap' be prepared to give examples, brand names. I assume that you mean a plant based liquid soap, free from fragrances and dyes?"

So do I - especially since I killed two camellias by using dish-washing liquid that must've had some extra ingredients (duh! talk about careless! I should've tried it on a small part of the plants first.)).

Since then, I've used Dr. Bronner's Pure Castile liquid, without any problem. I'm confident that other Castile soaps - either liquid or solid - would be just fine - as would Ivory, no doubt.

.

"My favorite home remedy for PM is 1 T. baking soda, 1 tsp. horticultural oil, 1 tsp. insecticidal soap, and 1 gallon of water."

I've not used oil, since it seems that (and sounds like) it would introduce unnecessary problems.

Relatedly, several sources I found said that Baking Soda is ineffective without horticultural oil!