LOL the first time I saw dog vomit slime mold, it was all over my mulched garden, even on the fence posts. I thought the deer were throwing up from eating something in my garden. Hah! Serves 'em right, I said! But no, the deer just keep on eating everything in sight, and it's just a mold. BlueBars

Judy, the foam protects them from any chemical you might use. If your hydrangea is the size you describe, you can spray away the foam with water, or take a paper towel, wipe them off and squash. You're going to find a little green to yellow-green soft nymph inside the foam. The nymph is sucking sap, causing the distortion. And when you're done with your hydrangea, you can come and do my lavender - they are covered this year, along with the hardy fuchsias :)

For future reference: I am now pretty sure these were indeed spider mites. I sprayed the plant heavily with a solution of 1 teaspoon dish soap in 1 liter of water, being especially thorough with the underside of the leaves. I did this twice, three days apart, and the problem seems to have been resolved. I never saw any mites on the plant. However, it spread to a couple of nearby plants, on those I could see small black specks underneath the leaves, which appeared to be spider mites. Luckily, it seems the spraying has been more successful then I could ever hope, and all the plants now look clean.

Unfortunately, it's challenging to impossible to get southern blight under control. The white you have *is* southern blight. See this at Oklahoma State http://www.ento.okstate.edu/ddd/diseases/southernblight.htm Here is a link that might be useful: southern blight