Just because I'm somewhat stumped, I thought I'd throw this up here and see what y'all can come up with. Last Saturday evening, I used bug spray on some wasps' nests outside the entryway of my house. Then, Sunday night after dark, (I'd been at a friends place watching football, or I'd have done it in the light), I took a hose and shot down the dead nests. Monday morning, before sunrise, I took the dog out in the front yard, and I noticed in the porchlight that there were some brown, drippy stains in several places on the siding. None of them directly corresponded to places where the bug spray was used. In fact, on one side of the house, they were in a kind of repeating horizontal pattern at about shoulder level. Anyway, in the limited time I had before going to work, I took some bathroom cleaner and an old sock, and tried to get the stains off. I got some of it, but it was really persistent, and seemed to be dry. Last night, I noticed that some areas of the remaining stains seemed to be wet again. I got a burr under my saddle and went out again, this time with a strong brush and car wash soap, (which said on the bottle it was OK for siding), and I went to town on these stains. When I was done, you'd never have noticed them unless you already knew where to look. My arm is still sore. And finally, this morning, I went out to look at my handiwork, and was shocked to find that, once again, there was a fresh area where one of the stains had been... more of this brown material, still wet to the touch, with no discernable odor. I wiped it off. Now, I guess the obvious explanation is that the bug spray is reacting with the vinyl. What I don't understand is why it's happening where it is,(in places where I didn't even spray), why it's persisting, and what, if anything, I can do about it. Any thoughts?