Help! Pea stems broken or eaten?

The stems on almost all of my pea plants "snapped." I assumed they broke because they were trellissed (sp) against a fence, but the same thing happened to the ones with trellissing that I've used in past gardens in other locations. Could there be something eating the stem? The separation occurred about 3-5 inches up.

Help. I peas and I'm devastated. I want to try a fall crop. TIA