rhubarb leaves

Large crinkly dark-green leaves are unfolding on all three Rhubarb plants.

Some have tears or holes in them.

I can't tell if this is from insects eating at them, or they tore themselves when unfurling (does that happen?) I suspected slugs or pill bugs, but find no sign of them- no sticky silvery trails, no bugs actually on the plants, no pill bugs scurrying away when I brush the mulch aside, no bugs apparent when I search at night by flashlight. Well, they look healthy and are growing fast, so whatever it is I hope it's not doing too much damage.

I know rhubarb leaves are poison to people, cats, etc. Do they also kill the insects that try and eat them?