This is the adult Vine Borer Moth. She lays her eggs at the base of your summer and winter squash plants, and when the eggs hatch the disgusting maggot-like worms tunnel into the hollow stems, eventually killing the plant.
Our zucchini are loaded with flowers and tiny zucchinis right now, and I don’t think I have the patience to perform surgery on them this year. We planted about five times as much zucchini last year, and this year it looks like the smaller amount is going to be much more productive.
By the time the borers wreak havoc on our plants, I think we’ll be sick of zucchini. I’m not sure how to prevent these without using chemicals.