Do they smell 'off' and mildewy? I've not yet met a mildew or mold that didn't give off some sort of scent. As I do not know where you are located you could be in the western states, in which case what you've encountered may be a normal trait of the Blue Elderberry fruit. I don't know if its possible to have multiple links posted at the bottom, so pardon the ugly url list. Here are some photographs of what the berries can look like. I should have thought to take photos of my own when processing. http://oaklandlocal.com/sites/default/files/i/elderberries%201.jpg http://stitchandboots.files.wordpress.com/2009/10/elderberries-macro-2.jpg?w=450&h=390 Note how in the first image, not all of them appear with the blue or whitish powder on them. They can all have it, or some clear black ones can be present - even entire separate clusters of them on the same plant. It does not rub off easily, and you'll likely just tear the skins off if you try. Something I found on accident that will make it disappear is sun exposure, once picked from the stems (don't know if it works when the berries are left on). If you're unsure if its mildew still, try leaving them in the sun for half an hour or so on a reasonably warm day - if they turn shiny and clear black, it wasn't mildew. I've also included a link below to some information about the specific species I'm talking about, Sambucus cerulea. Here is a link that might be useful: Sambucus cerulea - blue Elder

A "new" disease is messing up walnuts in the western states which is called 1000 cankers disease. I suggest you have a certified arborist or two out to evaluate your tree. You can locate a certified arborist in the Yellow Pages under the heading of Trees or something similar. A certified arborist gains that title because s/he passed a test and must submit continuing education hours.

It definitely makes sense. Especially in cases like Bart and Mad Gallica describe. In my yard, I seem to only have issues with powdery mildew when it becomes more humid (here - that means rainy), but when it's still warm during the day and cooler at night. That usually equates to early fall. I don't seem to have issues with it during the dry heat of summer. The powdery mildew I just found on my roses that weren't mulched was the worse I can remember. And it really wasn't that bad. It was probably the worst on Iceberg of all roses! Bizarre! That one never gets mildew in my yard. I usually keep my roses very well spaced and mulched, with drip irrigation. I think that has really helped. I don't spray (usually). I have only really purposefully gardened in Northern California though, and our conditions are so different from most. I'm inland with a lot of dry heat ... and over the last few years with such severe drought conditions and weird climate changes. Although, since I found these forums I was thinking about squeezing everything together in order to fit more roses in! On second thought, I'm going to pull back and stick to my usual spacing after all. More roses will not be better if they're covered in mildew. More disease maintenance and pest control takes all the fun out of it! Thanks for explaining Roseseek. Nature using mildew and rust to help the plant defoliate in order to survive colder or hotter/dryer climates makes total sense. Your explanation for how mulch helps ward away mildew makes sense too... and fits with your explanation of what causes mildew. It's wonderful and invaluable to have such knowledgeable professionals like you on these forums. Thank you so much for making yourself available and sharing your wisdom.

^^ Some squash varieties are bred to have some resistance -- butternut at least. I thought some kabocha too, but maybe I'm wrong there. Didn't have a lick of it last year, but I got wiped out by it year before that -- I had to harvest the kabocha early because the vines actually died from the mildew it was go bad, and the flavor hadn't fully developed and they didn't store very well. That is my concern -- I've got a lot of beautiful, tasty-looking squash out there... I'll have to look into a preventive spray next year if I can't find any resistant varieties of kabocha. Interestingly, the cukes from the seed DH bought had the mildew, but the other vines from the seed I bought didn't have any at all, even though they were intermingled on the same trellis. Maybe the variety I ordered does have some resistance bred into - easy enough to find out by looking at the seed packet (but that would require me having to find it buried somewhere in the big pile of packets I have - maybe some other day when I remember).