Hi George,

Squash vine borers are one of my least favorite pests.  They are extremely frustrating. 

Here are some links to information on the vine borer that might be helpful:

From the University of Wisconsin, for commercial growers. 

Also from the University of Wisconsin, but for home growers. It has some good practical tips at the end. 

Note that UW says "They emerge as moths in late June and July, when 900 degree day 50 have been reached." You can find out when we have reached 900 degree days by using the MSU Enviroweather website. Here is a direct link to the regional degree day summary. You can see on the chart "degree days base 50F current." Next summer, you can check that chart to see when you are getting close to 900 degree days and plan your control approach. 

Here's an MSU article with a picture of the eggs on a stem. You can scout for and remove any eggs that you see on your plants. The insecticides listed in this link are for commercial growers. Insecticides seem to be largely ineffective for home gardeners, especially once the larvae tunnel into the squash stem.

If you are only growing a few squash plants, you can try planting them in pots and covering them with a row cover (tucking it under the pot). Planting them in pots has the benefit of you changing out the soil annually so that the larvae cannot pupate in the soil and fly in the spring. 

You might try very short season varieties and try succession planting. There are varieties of summer squash that only take 41 days to reach maturity. You should have a first crop harvest before the vine borer moths begin flying. You might even be able to start a new crop and plant them outside after the adult moths have finished laying eggs for the season. Or, plant them outside, and use row cover to protect them until the adult moths are done for the season. 

It's important that you destroy infested vines. It's hard to do when your vines are still producing, but if you want to reduce the number of pupating larvae in your garden soil, you should pull the vines while the larvae are still inside the stems, and either put them on the curb for composting or put them in a black bag to "cook" before adding them to your home composting system. 

I hope this helps! I'm sorry that there's not an easy, straightforward answer.

Lindsey K. Kerr, MS, MHP (she, her, hers)
Consumer Horticulture Educator
Michigan State University Extension