Trouble ahead?

I spent all day Sunday working in the garden. I planted helleborus ("hellebori"?), hostas, violas, asters, gaillardia and cleaned up in a number of areas. I also spread some of that castor oil-based stuff to counter the onslaught of rodents.

However -- this morning as I went out to re-fill some birdseed, I noticed the appearance of a number of webs in the small trees with an explosion of catepillars. I immediately grabbed some spray and covered the web and limbs with the spray. But I haven't seen this many webs in my yard before.

Not a good sign.