How to prevent/cure powdery mildew

My Lilac gets powdery mildew over its leaves each year and since my yard is small plants nearby catch this sometimes. Some of my young hibiscus seedlings got it so I moved them but I want to know if there is anything that can cure it?

Not cure, but prevent. Here is a link about PM.

http://www.ipm.ucdavis.edu/QT/powderymildewcard.html

Two effective organic approaches would be sulfur or copper on 7-10 day intervals at first sign of disease. You could start applications now to protect new growth this year and reduce powdery mildew inoculum for next year.

Powdery mildew favors hot dry conditions unlike downy mildew which is favored by cooler and wet conditions.

drobarr, could you give us some links for research, please? Here in So. Cal. coastal zone, we are used to powdery mildew during the spring, when weather is cool and damp. This year, it is still spring weather in Aug., and mildew is rampant in my garden. I just read that downy mildew is a recent arrival from UK, so what you said confuses me, and how does one tell them apart?

Here are photos of whats wrong.

You definetly have powdery mildew. Powdery mildew is usually on the tops of the leaves whereas downy mildew is on the bottom of the leaves.

Water on the leaves can often prevent powdery mildew from forming and spore germination. Here is a good link that explains the conditions most conducive to powdery mildew development: http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/powdery-mildew-cross-listing

Here is another article...you can find hundreds that state that hot dry weather exacerbates powdery mildew. http://www.ext.colostate.edu/pubs/garden/02902.html

In my area in hot dry summers I have lots of powdery mildew and in cool wet summers I get downy mildew in apples, cucurbits, and many ornamentals.

Most places on the west coast the humidity is too low for downy, unless you are coastal San Francisco and north up to Canada (western side of the Cascades).
http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/downy-mildew

Powdery mildew does benefit from high humidity and so in your area you may only have high humidity when it rains which allows the powdery to get started.

Downy mildew has been in the USA since colonial times.

This message was edited Aug 22, 2013 12:49 AM

I will ditto the info about PM being reduced in the hottest weather.
Here one of the worst plants for PM is Crape Myrtle.
The original species (Lagerstroemia indica) is very susceptible. To the point that I no longer spec any variety on any landscape project. The old one in my yard gets it every year, and it never really quits. I am in a milder part of zone 9b, some coastal influence.
In other cities a bit inland but still where I go to work the Crape Myrtles will show PM in the spring, then less and less as the summer warms up. But, since most of the leaves are grown in the spring, and less in the summer when the plant is budding and flowering, it still looks like the whole plant has PM. You have to look closely to see that the last few leaves that came out do not have PM.
PM does best in mild, dry weather, and is quite capable of growing between rain storms. We normally have rain in the spring separated by enough dry days for PM to thrive. Not a lot of foggy or misty days. It gives the impression that PM thrives in moist conditions, like many other fungi.

The hybrid Crape Myrtles are resistant, and do just fine in all the areas I work, so these are the ones I choose from for landscaping.

We always see downy in the spring and late summer here in the Northeast and the powdery in the hot dry mid part of summer.

"Powdery mildews are most severe when the weather is warm and dry"
http://www.uri.edu/ce/factsheets/sheets/powderymildew.html

"into the hot, dry conditions that promote powdery mildew. Unlike most fungal diseases, powdery mildew is not as destructive when rains are frequent"
http://hyg.ipm.illinois.edu/pastpest/200210b.html

"powdery mildew, which appears in hot, dry weather when days are extremely warm and nights are cool. Downy mildew is common during cool, wet weather."
http://www.ehow.com/info_8548654_cause-cucumber-leaves-turning-white.html

"Unlike other disease causing pathogens, the powdery mildew fungus prefers warm and dry but humid conditions. In fact, rain can wash the conidia off leaves and conidia will not germinate in freestanding water."
http://www.omafra.gov.on.ca/english/crops/hort/news/orchnews/2003/on0203a6.htm

I suppose the east coast difference is that when we have hot dry weather, we also have high humidity which in California you don't. Especially if you have a Santa Ana. So in your hot dry conditions you wont have any disease including PM. It seems that the strains there have adapted to cooler temperatures when humidities are high after a rain as the only opportunity establish themselves.

So am I supposed to keep plant wet or keep leaves wet? Is there something I can spray on the leaves to help it recover? I don't know anything about what's used to help so I need some product names.

Keith,

Here are some products that are organic that are effective at contolling and prevently powdery mildew:
Serenade http://www.jungseed.com/dp.asp?pID=50297
Copper http://www.jungseed.com/dp.asp?pID=73744
Sulfur http://www.arbico-organics.com/product/sulfur-plant-fungicide/1002
Neem oil http://www.tastefulgarden.com/store/pc/Fruit-Tree-Spray-Concentrate-also-for-Vegetables-12p154.htm

Most of these same items can be found at local hardware stores or garden centers.

Copper is great because it is natural and has both fungicidal and bacteriacidal properties and is very broad spectrum. You also provide some nutrients. Good choice. Let us know how it goes.

I just wanted to say it has worked wonders. All symptoms vanished within a week it was amazing, plants suddenly started growing healthy green leaves and are looking great!

what product did you end up going with?

clorothalonil is a very good broad spectrum fungicide