Plant diseases are a function of 3 things present at the same time and in the correct amounts.

They are:
1. susceptible host plant (to my knowledge, all lilac and squash are susceptible) etc)
2. the disease organism (various powdery mildew fungi exist in your environment at all times; some are specific to certain plants while others specialize in attacking one or several hosts)
3. a suitable environment (light, temperature and moisture levels must be appropriate for the disease to occur)

So, I'm sorry, but I have to burst your bubble. The manifestation of disease comes and goes -- it comes when all the above 3 items are appropriate but it goes/stops when one or more of the 3 items change.

Put another way, the environment changed and the powdery mildew has stopped attacking new tissues.

For everything there is a season ...

>They are:
1. susceptible host plant (to my knowledge, all lilac and squash are susceptible) etc)
2. the disease organism (various powdery mildew fungi exist in your environment at all times; some are specific to certain plants while others specialize in attacking one or several hosts)
3. a suitable environment (light, temperature and moisture levels must be appropriate for the disease to occur)Well, yeah, I live in Philly, extra hot because it's a city, and extra humid this close to the shore, so I figured out where the mildew came from when it first showed up. (Actually, first showed up last year on the lilac, but pulling leaves off worked until the fall when the leaves fell off and I removed them from the container.)

>Put another way, the environment changed and the powdery mildew has stopped attacking new tissues.My garden is outside! Environment can't change during gardening season, unless we end up with nuclear or volcanic winter. (I'd rather not. LOL) I will agree the mildew has stopped on our squash -- they died! You can only pull off so many leaves before the plant simply doesn't have enough to feed itself through photosynthesis, and the blasted mildew sucks the life out of the whole plant on the plant's leaves if you don't remove them. (Poor plants - damned to die by either of those methods! I've been trying to find added info on the pest since the first blotch showed up on the lilac, too.)

The link is to a scientific paper that reviewed a variety of sources for experimenting with baking soda. It also ended by quoting several experts, who have, apparently miraculously changed environment across the globe. (I don't think so, since P. Allen Smith lives in an even hotter, more humid location then I do.)

No bubble bursted! I recognized enough of those experts to know they really are experts, so will trust them and keep my lilac growing by fighting the mildew -- if necessary, for the rest of my life. I guess the only thing I need to worry about is who to will it to after that. LOL

I am wondering something though, "Exactly how is it that almost every forum I've visited on this site has one or two 'experts' so certain of their expertise that they disqualify anything that they have not personally experienced even without bothering to read what the rest of us write carefully, the links included?"

If I were an expert, I wouldn't have been sharing this info for others with the same problems I'm facing. I would have already known and written it in a quicker, easier to understand format. As an expert (in an entirely unrelated field from horticulture), at least I have the common sense and civility to know better then to try to destroy another human being's dignity, as you have gleefully tried. (I'm way too old to fall for such silliness, and I don't even qualify as "senior citizen" most the time. LOL)

When someone else is beginning to learn the things I've been studying for decades, and shares their knowledge or asks questions, I get excited to see him/her get interested in what excites me. Bursting the bubble?! And, honestly, really just pretending to burst the bubble -- for what purpose? To puff yourself up? Rather backfired.

Thank you for the lesson on the causes. I suspect they might have taught interesting info to others. I just hope they could take the info, remember it, separate it from the "manure," (pun intended and enjoyed) but don't confuse the rest of what you wrote for facts!

I am a born and bred Yankee, so have the manners of one. I did live in the south for a year when I was younger, and learned a good adage for you to consider, "you get more flies with sugar than with vinegar." Only thing you need to remember is that bull works just as well with flies, but doesn't do much for people!

The best I can hope for is that you just had a bad day today. Me too. Hopefully the next time we write to one another it will be on good days!

Valentinetbear - thanks for the baking soda link. I had horrible PM on my Monarda this year and finally ended up cutting it back to the ground...you're right about there being a limit to how many leaves you can pull and still have a living plant. LOL. My poor Monarda was nearly naked.

One thing I'd like to mention, though, that sort of backs up the point Jean was trying to make with her post -- that is, my Crepe Myrtle gets PM on it every year and it eventually just goes away on its own. I don't treat it. Environmental conditions play a role in promoting an attack of PM on my Crepe Myrtle and a change in those conditions cause it to go away eventually. I believe that's all Jean was saying, but you took it the wrong way. I don't expect a treatment of baking soda to prevent or "cure" the PM on my Monarda, but I am hoping it will lessen the severity and help to make the plant look better -- so I don't have to whack it down again next year when it gets PM.

Now, with all that being said, I really must add that I think your long verbal attack on Jean was uncalled for. I've never known her (I'm guessing Jean's a "her", pardon me, Jean, if you're a "him") to be rude or unfair in her posts. I've never seen anything in her posts that would indicate to me that she was trying to "puff" herself up, or make herself feel important at the expense of another poster's feelings. (though there are some members here at Gardenweb who do that....not naming names) I think you were way off base with that accusation. Jean is a very helpful member of Gardenweb and has helped me several times since I became a member.

Keep in mind that it is very difficult to decipher the "tone" of someone's words in an internet posting.

Thanks again for the link.
RENEE

Very often a gardener will yank out plants that are bothered by Powdery Mildew when the cure is as simple as spraying them with either a mixture of 1 teaspoon of baking soda in 1 quart of water, or a 50/50 mixture of fat free milk and water, about every 5 to 7 days. As a general rule PM is more of a cosmetic problem than a harm to the plant, although if it progresses far enough it can cause witling of the affected leaves.

There are good number of very experienced gardeners that post on GW - many are highly trained horticulturists that practice "gardening" on a professional level and deal with the issues that are brought up on this forum (and others) on a daily basis. Many are just as experienced, if not more so, in dealing with plant pests and problems than the so-called "experts" quoted. Jean001 is one of these individuals and her contributions to GW over the years have been enormous. Your disparagement of her information and advice was inaccurate, unnecessary and uncalled for.......I think it is a bit of a case of a little knowledge (yours) being a dangerous thing.

Powdery mildew IS highly affected by cultural conditions (how and where the plant is growing and the care it is given) as well as the climate and certain plants are much more susceptible to the problem than others. The growing environment CAN be changed or altered. Improving air circulation, providing the correct amount of sunlight, practicing good garden sanitation and reducing humidity by correct watering practices can all affect the spread of the disease.

As far as applying any kind of treatment is concerned, fungal diseases are not cured by spraying - in other words, the powdery mildew will not miraculously disappear if you use a baking soda or milk solution or even a more high-powered chemical fungicide. Fungal controls are preventative only, not curative, and the treatment must begin before you see visible signs of the problem. At best, once the powdery mildew is evident, you can only hope to control its spread to otherwise unaffected foliage or new growth. So any kind of "after the fact" application is merely palliative. The good new is that few, if any plants, are killed by powdery mildew, although if widespread enough it can seriously weaken some, primarily annuals. It is largely cosmetic in nature.

Understanding the pathology of plant diseases and how to correctly address them takes a great deal of specialized training and is not something that can be easily learned from reading a few websites or picking up a couple of Internet tips. You would do well to follow the advice of those who have benefitted from such training, such as Jean001, rather than run them down. It only demonstrates your woeful lack of understanding.

With some basic information regarding the life cycle of powedery mildew (and other plant diseases) you'd learn (as Jean001 was patiently trying to explain to you) that this disease is almost entirely preventable.

My delayed apologize, Jean, and all. I really have had a bad week (including my poor squash dying the same day I found how to keep that from happening.) Even the delay in apologizing tells a bit of how my week was going -- would have apologized sooner, but had a couple of teeth yanked out under anesthesia, followed directly by our DSL going down for over a day.

I sppsrently am missing something still. I assumed the mildew was coming on the plants (from spors carried all around here) because the plants weren't getting good enough air circulation, so moved both comtainers (ones in the front of my house and ones in the back) out into the open as much as that is possible constrand by by the size of my space. This did nothing for either of them. That is the only change that can be made in the environment, so I apparently must be missing something I just didn't get. Now it's showing up on our cukes and pumpkin!

Add to that, the dwarf lilac is just over a year old, and the only way the PM stopped finally last year, was in late fall when the leaves fell off. With that the only thing that has stopped this PM for me is death or winter. It seems some have managed to have their plants survive from this year after year, but once some of my plants die from a parasite, I'm beginning to think if this baking soda thing doesn't work, tossing the poor lilac into the trash is the last option.

I simply do not understand your responses to the article linked to meaning little, considering the article does say it has worked in a variety of applications from crops to garden plants.

From the reactions I've received, I do trust I'm missing something important, and have blamed Jean. I truly am sorry and I truly do want to understand. anyone up to trying to expalin what I'm apparently missing?

Valentinetbear ~ kudos to you for coming back and apologizing. We all have crappy days every now and then -- and getting teeth yanked out most definitely qualifies as "crappy".

I'm no expert and I'm afraid I couldn't do much more than guess as to what's going on in your garden. I remember reading in an online article a while back that PM spores reside in your soil and can attack your plants when conditions are right. It was suggested in the article that the soil at the base of the plants be given a drenching of fungicide and all debris on the ground around the plant, such as dead leaves, etc., be removed and destroyed.

Renee

Maybe this will help....

Here is a link that might be useful: Powdery Mildew Fact Sheet~ UCDavis

Powdery Mildew spores travel around on the wind and grow on many plant species when weather conditions are right. at one time it was though that watering the garden in the evening would cause PM, but through good research we know that is not true today. Over the years I have found that either the baking soda or the milk/water spray will control PM, signs and symptoms disappear from susceptible plant leaves after they are sprayed. While Cornell has found that Potassium Bicarbonate is better at controlling PM than Sodium Bicarbonate I've not found the Potassium Bicarbonate to be all the available to me. Sodium Bicarbonate is very and easily available to most anyone as is the fat free milk and water and both are very good at controlling PM.

Thank you for discussing the topic of Powdery Mildew. My tomatillo plant and snap peas have it. I thought it was white mold, then you all popped up in my search. Now, this could be embarassing, but when I saw the dusty stuff on the leaves, I thought "Self, what kills/curbs mold while not harming the planet?" I then thought about vinegar. It made some sense to me to go ahead and spray a solution of water/vinegar on the leaves, completely covering the leaves. I basically spray-washed the plant with vinegar solution. A Chef I am , but a chemist I am not, so I am hoping a real Gardener could comment on this action I took.... was is indeed smart or notta-so'a-gooood?

bgreen - I've heard/read that vinegar can be used as both a fungicide AND a herbicide. So I guess the answer to your question (smart or notta-so'a-good?) would depend on the amount and concentration of the vinegar you sprayed on your plants. Too much could burn the foliage severely.

Renee

I'm one of those commercial growers who got baptised on the powderly mildew issue with a lot of dollars at stake. My first outbreak was on poinsettias. I recognised it immediately before the powdery stage began and called my extension agent to come confirm my suspicions. He didn't think it was. Well, the whole crop bloomed with white leaves, and the aggravation and lost sales were very real. So, even the "experts" can learn a few things.

A lot of liner stock had been shipped out that year already innoculated and infected but just not in readily visible stages yet..... and in the next few years where good control was not given to the stock plants WHEN it was needed. You do not cure powdery mildew. You have to work at preventing it.

Jean was entirely accurate in her follow-up. Those spores are everywhere, all the time. The biggest thing you can do to prevent large outbreaks of it are to be proactive. Copper used to be used for this condition but it's not friendly to the environment, and not a thing home gardeners would really want to tackle. Even that won't clean up a crop.

Some greenhouse film manufacturers are trying to design films to transmit light in just certain controlled wavelengths of the spectrum, because that is how much PM is affected by the environment. The light conditions have to be just right, as does the temperatures and the humidity. So far, this new new tool has not been successful, because plastics degrade and the spectrum of light they transmit changes with age.

The baking soda reports have been around a long time, mostly since that big poinsettia outbreak hit the industry. It was concern from the commercial growers who prompted most of the research on ways to control this economic demon. Most of the time, for outdoor plants like lilac........control is just not even important, save trying to give them adequate ventilation. The next year, if the weather is different, then you may not even have an outbreak.

We haven't had PM common on poinsettias for many years, but just the word strikes fear in my heart. LOL. I can relate. Just don't put too much stock in baking soda curing it after the fact.

Calliope - As a commercial grower, you have a lot more at stake than a home gardener. There are systemic fungicides that are curative rather than preventative. I have used triforine in the past with good success. It has an LD50 of 16,000 which for all practical purposes classifies it as non-toxic.

Thanks for the heads up on that Bob. I'll make a mental note of it. I remember that year buying a copper based spray, the only thing I could get recommendations on by the pathologists I consulted. It held the plants all through production until they reached the display areas and then the disease went wild on one particular variety from one particular vendor. I was mortified. I replaced the plants for anyone who complained.....and most of the rebloom was after the holidays, and they'd already accomplished their purpose as decorations.

The stock has been very clean since that major outbreak in the industry. But, I still live in fear each November, waiting for it to happen again. LOL.

To Bob. When the disease evidenced itself in that particular crop, the plants were in bloom. That alone limits what can be sprayed on a plant, because if you nasty up the bloom, it can't be replaced. How save is this product on blooming plants?

Vinegar is an herbicide and should never be sprayed on plants you want to live.

Calliope,
My heart aches for you after-the-fact. I can't imagine going through what you've been through. I have been reading, with interest, a;though, you can tell from my zone and my comments, I'm neither a commericial grower, nor could ever consider growing poinsetias outside. I do something that might help you, too, particularly when you get to the age of getting and accepting "senior moments!" LOL

You wrote: "Thanks for the heads up on that Bob. I'll make a mental note of it."
You might consider writing it down some where you can easily find it. If you're anything like me, the moment I NEED a piece of information is the exact moment I discover that mental note was misfiled in my brain, never to be seen or heard from again. LOL

Regarding vinegar for use on plants: it's all about the dosage. There are many 'recipes' out there recommending the use of vinegar for the prevention and control of powdery mildew. I've not used it for that purpose, but have used diluted vinegar in my sprayer MANY times to acidify water. Mix (white or cider vinegar) at a rate of about 2 T per gallon of water.

Use full strength to kill foliage.

I just wish to point out, gently, that the "disease triangle" has (been) morphed into the "disease pyramid"; the dimension of time has been added.