I turned to google of course. The best resource I found was Gardener's Supply Company's fantastic Pest & Disease Detective. You select what type of vegetable and the location of the damage on the plant and it generates a list of possible pests and diseases affecting your plants. When you click on one of the possible pests it gives prevention and control options and recommended products that can be purchased in their online store.
According to the detective my pest is the cutworm. It suggests young plants be encircled with a cutworm collar that extends 2 inches below and 2 inches above soil surface. I have never seen or heard of a cutworm collar and do not plan to buy any. Why would I when I have a garage full of plastic yogurt containers waiting to be taken to the recycling center? The large 32 ounce containers are perfect repurposed cutworm collars. Just cut out the bottom, slip over the plant and push into the soil 2 inches.