One of the local churches has some juniper bushes with a problem. Slimy mostly-white blobs hang on some of the smaller branches. Each blob has a dark spot. They strongly resemble bird feces but have an entirely different texture. Bird feces dry out after a while; this stuff doesn’t. They vary from 0.25 inch (6 mm) to 0.5 inch (12.5mm).
I’ve done some googling of both the web and images but found no answers. I used variations on blob, glob, globule and juniper.
It sounds to me like you’ve got spittle bugs. The larvae attach themselves to the stems, suck on the sap, and then excrete the moisture in a frothy coating around them. There’s a pretty good picture of the slime on the Wiki page.
MikeS, do yellow jackets obsess on those things? I went to a casual horse show (not an oxymoron, heh) and hurriedly moved my horse and trailer when I realized my mare was swishing away yellow jackets that were swarming around a eucalyptus tree. I thought she’d stirred up a nest, but they weren’t angry–they were feasting (or cultivating?) on these white globule things on the underside of the tree’s leaves.
I’ve been meaning to post over here in GQ about it but kept forgetting–now someone else may have posted a question that yields an answer for both of us.
I don’t know what habits yellowjackets might have regarding spittle bugs, but I’m pretty sure that spittle bugs only feed on the stems of plants, not the leaves. So my guess is that it was something else the yellowjackets were interested in.