My battle with squash vine borers started last year. They ruined my squash, zucchini, and cucumbers. This year, I've done lots of research, and I am fighting back. I found a great post from a gardener in Texas who keeps a wonderful gardening blog called Rock Rose. She's been documenting her fight with the vine borers, and because her plants are about a month ahead of mine, I am learning what to do ahead of time. She's even found a squash vine borer moth in the act of laying eggs!
So, how do these awful bugs kill squash? A full grown larva or pupa will overwinter in the soil one to two inches below the soil surface. The larva pupates in the spring, and the orange and black moth emerges from the soil and lays eggs on the stems of squash plants. One to two weeks later, the larva hatches and quickly bores into the stems of the squash plant. They usually leave a trail of orange sawdust-like frass at the entry point. Inside the hollow stems of the squash plant, the larva feeds for 14 to 30 days before exiting the stem to pupate in the soil. In Mississippi, there can be up to two vine borer generations per year. Ew!
My fight this year starts with removing the eggs. I found and smooshed five eggs earlier this week and two more today. To show you how small there are, I left a piece of pine straw in the second photo. I've read that these eggs are only 1/32 of an inch!