powdery mildew infestations?

ianna(Z5b)October 1, 2007

Is it me, or has there beeen a large infestation of powdery mildew this year? And I can't understand why it thrived in my new garden bed area. It's in a sunny location, watering was kept to a minimum and there's plenty of wind movement... Right now, a garden phlox literally got covered with mildew overnight.

I also had problems with those worms than tunnel through leaves (can't recall the names of these things)

What other pests have infected your areas?


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I have had the usual pests - the rose sawfly and the leaf cutter bees. Do you know how pathetic a rose bush without leaves but gorgoue flowers looks? There were also some rabbits but I think the dogs scared them away. I usually lose a lot of my rose canes to them. As for the mildew, I usually don't worry about it this late in the year. The plants that usually get it are the honeysuckles. I'm surprised I get it because this area is very open and windy. The only plant I have that has it is 'Miss Pepper' phlox who is supposed to be mildew resistant, key word being resistant. Despite that, she is the only plant that has it and she is covered.
You said that you had worms that tunnel through leaves. Do you mean leaf miners? They leave the white lines on the leaves. I just pick off the leaves and put them in a pail of water. Marg

    Bookmark   October 1, 2007 at 4:16PM
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bonniepunch(USDAz4 AgCanz5a)

Leaf miners - and I hate them! I usually have them, but not this year - strange. And yeah, the powdery mildew was awful this year. It attacked some Liatris so badly it didn't even flower. Phlox is something I've given up on growing because it always gets it.

I had problems this year with slugs. I must have picked hundreds off my plants, there were so many they were even coming in the house! Wasps also chewed up my plants more than usual - I saw a lot more of them then I normally see so I must have some nests nearby.

Other then a few aphids here and there, and a few lily beetles, I really didn't have any other pests. Not counting the squirrels of course...


    Bookmark   October 1, 2007 at 4:48PM
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Leaf miners. I'm been trying to remember the correct name. Thanks. These got into my columbines and to my creeping veronica. Hate them. Had to chop down all the foliage.

It's the powdery mildew infestations that is really bugging me this season. I hope it doesn't return next year. I chopped down an large false sunflower in an effort to control the mildew. My coreopsis moonbeams have also been affected.

I also think a raccoon has been visiting. I saw a pile of something in the driveway. I also saw some dropping which I suspect came from a squirrel -- probably trying to get to my tulips.

    Bookmark   October 2, 2007 at 4:15PM
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nyssaman(Z6 ON)

heat and humidity

    Bookmark   October 6, 2007 at 10:04PM
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Not much you should bother doing about powdery mildew this time of year. Once you have leaf drop or a hard frost you should try to remove as much of the leaves from the area as you can. Leaving them around the base of plant through the winter will re-introduce the mildew on the new foliage next spring. Same with your perennials - I would trim them down to a few inches, remove all infected trimmings from the area and cover with mulch for the winter.
In the spring when the leaves start to break give them a light coating of neem oil (available at most nurseries or hydroponic shops). The leaves will be pretty delicate at this stage so use the weakest recipe on the bottle and spray when it's going to be overcast for a day or two or in the later part of the day when the sun isn't as intense. The oil on the new leaves can burn or scorch them. But this works! I had an old rose bush that was so coated with powdery mildew it looked like someone sprayed them with that fake snow stuff. Within a couple of applications of neem oil the powdery mildew was completely gone. Neem worked well on my perennials, too, in preventing mildew and also helped keep the aphids and slugs away! Neem oil is great stuff and is highly underrated. Is also safe to handle, works like other horticultural oils if you have any experience with those.

    Bookmark   October 18, 2007 at 12:39PM
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Until recently, I realized we did have a bit too much humidity. Still something is out of balance for mildew to be this widespread.

I'm afraid the infestation has affected even the grass lawn - so it is widespread. My phlox did develop mildew overnight, as did the echinacea white swans, the coreopsis moonbean, the delphiniums, the zinnias. But it has managed to leave the roses (David Austins)unscathe. I have learned that Davidii phlox are mildew resistance. So I will be replacing the affected phloxes with this variety next year.


    Bookmark   October 18, 2007 at 8:52PM
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Hi all you people covered with white powdery stuff....

I have been battling with powdery mildew for years in a very mixed perennial garden...and so far haven't used anything but have done a lot of reading and observing.

First: DO NOT water late in the evening and avoid overhead watering IF you can....You can see the overnight results sometimes from mid summer on if you water late in the day...hard to avoid sometimes, I know. The plants must dry quickly to avoid becoming infected.

Good ventilation makes all the difference for SOME plants but there are others that are famous for being susceptible to powdery mildew no matter what you do. Still others seem pretty much immune and many fall in between.

Summer Phlox is the most famous of all for attracting powdery mildew. I only buy Summer Phlox that say they are resistant. The White Davidii, as someone mentioned is a wonderful phlox that blooms early and strong and has never been a problem in my yard. Two others also stay clear of it. One that I thought was supposed to be resistant had some powerdery mildew this year (Nicky-a purple) and also didn't flower. Powdery mildew not only looks crumby but has a big effect on the flowering and vigour of SOME plants....(Some others seem to tolerate it.)

Another plant that I can count on having the dreaded PM is fall aster. Thinning early in the season and keeping it well watered helps to keep it from getting severe-- but get it is does. Never seems to effect the flowering of these though. But of course this is blown in the wind, tracked on the feet (look out grass!) and can spread easily around to other things.

Monarda is another perennial that has a reputation for susceptibility amongst the older varieties. In fact, I yanked a red one out all together because of that. As with the summer phlox, there are now good Monardas that are resistant. I now have a large purple one that has remained absolutely free of this fungus and isn't as rampant growing as some of the older ones either..

If you are under the impression that high humidity and moisture will increase powdery mildew....I don't think so. I find that I rarely have a problem in well watered, cool areas. But often do in extra dry areas. ...well ventilated or not. And I am located in the semi-desert area of the North Okanagan of B.C.

Personally, I will not use any of the commercial stuff that is recommended so casually in older books for controlling everything under the sun. The only thing I might try IF I was desperate would be something I first saw recommended by Rodale's Chemical Free Yard and Garden (publisher of Organic Garden Magazine). A mixture of baking soda and water with a tiny bit of cooking oil added to help make it stick. I expect that works as I have great faith in Rodale's research, but like I said haven't actually got around to doing that. It is recommended that you spray this on AS SOON AS YOU SEE IT DEVELOPING as it is more effective to catch it early. You might need to repeat after a good rain.

    Bookmark   November 5, 2007 at 7:38PM
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Well, in my front garden, the primary agent that brought this pest into my yard was a false sunflower I had purcahsed from a grocery store. By the time it started showing the disease, the infestation reached my phlox and then the white swan echinaceas and then my okras, then affected just about all the other plants in the front yard, including my tickseed and the delphiniums. Interestingly, the David Austen roses remained resistant.

Also adding to the woes, we were on water conservation modes - had to water on certain days and even then at certain periods only. Unfortunately most rules required we water either very early in the morning (when we rush off to work) or late in afternoon towards evening. So it created the ideal humid situation. So my thoughts are that next year I will instead water close to the roots & avoid overwatering (which is a waste of precious water anyway)

My most immediate step, now that we are at the end of the season, is to cut down all teh affected plants and throw these infected branches and leaves out with the yard waste. Come spring the mulch will be removed because I suspect mildew spores would have fallen on them just waiting to be revive once again.

I will also replace my garden phlox with the Davidii variety. Yes I've heard both sides of the story but I've had some previous experience with the variety and note it is able to resist the pest. It's only unfortunate I hadn't thought of it sooner.

I suspect that the right humidity level can promote mildew but once it starts thriving, it gets most of its moisture to survive from the stems of the plants. What's more when it gets dry, it's prime for spores to fly off with the wind and latch on to it next host plant.

By the way, I've been to the Okanagan before and I must say it is one of the loveliest places I've been too. Near a lake and thriving orchards everywhere. In fact, I was very impressed by the gardens people had in the area. I recall sweet air quality. Although it is a semi-arid location, you do get good moisture from the nearby lake, thru evaporation.

I will try the Rodale method, that's actually a good suggestion. - I suspect that the higher the acidity (or alkalinity?) is detrimental to the pest. And you are absolutely right, kill off the infestations as soon as it's spotted.

    Bookmark   November 8, 2007 at 11:04AM
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This year powdery mildew came to visit me in quite a fashion. There were a couple clumps of monarda in one of the front gardens A row of 50 lilac trees along one side of the building with a new rose garden planted in the back. I watched for it to come and when it did I realized I would never totally wipe out this pest on the whole property, what with having only two hands and all, so I decided to try to contain a small group of plants and keep them mildew free. I used the baking soda warm water and murphy's oil soap concoction on a strip of ten trees and really focused on the centre four. I worked this routine on the lilacs every five days for a month while the monarda mildew spread to the delphiniums and started their attack on the white phlox which I must say fared the best of the three. The mildew on the lilacs was at best slowed. Interestingly, the rose garden, which only had just begun to enjoy the company of the mildew, was joined by aphids, and an old friend rust before being introduced collectively to Mr. Safer's End-All 3 in 1 miticide, fungicide, somethingelseicide and deciding to move the party elsewhere. Two months later, when the Safer's hospitality was no longer offered, the party resumed. Next year I'll try to catch the mildew earlier and offer up more resistance. This year I'll clean up the fallen leaves and move them far away.

    Bookmark   November 23, 2007 at 4:34AM
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cookie8(zone 5 ON)

That's probably what took care of my Phlox too. I still have the receipt for if it doesn't come back. I didn't get one spot on my Zinnias which really surprised me!

    Bookmark   November 26, 2007 at 8:58AM
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