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Diatomaceous earth only works when it's dry, fyi, so that can be tricky directly in the garden where things are bound to get wet.
I've heard that peppermint essential oil can deter insects, but it does come with the side effect of smelling like you live inside a diner mint, for better or worse.
Oof! Good luck. I gave up most years because they're such a nuisance. I did have small luck with vinigar and peppermint, but only very small.
Also, grasshoppers...holy halibuts, batman! I've never seen something sheer gourds to nothing like this year. So even trying gourds to deal with the squash bugs didn't work.
Oh boy you're in for a battle. We've had squash bugs now for the second year and they are aggressive and once they've produced a few generations they are near impossible to get rid of. We've gotten to the point where we're not going to plant any squash for a couple years because they overwinter in the soil.
Your best bet is to get the eggs off the leaves before they hatch. I like to use a piece of duct tape to pull the eggs off. If you get to it early you can stop an infestation. But if you have eggs on nearly every leaf then it's too late. Even with heavy pesticides the cycle is hard to break. If the eggs hatch you can still kill the nymphs pretty easily with natural things like diatomaceous earth or Castile soap spray, but once the nymphs molt and turn to adult they cannot be killed without something like sevin pesticide (which will also kill beneficial bugs.)
Good luck.
Next year, they planing strongly scented mint-family plants between squash plants. Mint, rosemary, sage, etc. will deter reduce pest activity, though it usually won’t work 100%. I like to use lemon balm just so I can snack on it when I’m tending the garden.
Mint can be pretty invasive depending on where you live. We have a smaller bed near our house that it's basically taken over, but that's largely OK with us. I would hesitate to put it into the ground in my raised beds.
That is true…
Does work though. I used it near strawberries for the same kinda effect and it does keep insects further away.
I ended up pulling it all out though cause the creep was getting bad. I feel like lemon balm or citronella is gonna be my next test.
Cool to hear it works! It doesn't grow that high, so as long as it makes for a decent companion plant it's not a bad idea.
Thanks for the suggestions, everyone. I'll probably be trying praying mantis and lady bug eggs and planting nasturtium as a companion plant. I'll also pick up some neem oil if those fail. If nothing else works, a few years without squash for me.
This year I tried insecticidal soap, applied weekly. I don't know if our infestation last year wasn't that bad, but it seems to have done the trick.
If you want to limit your pesticide application, you can put out traps for the adults. You won't catch them all, but you'll know when they show up. IMO, it's easier to watch traps than it is to look for eggs. When the adults show up, start treating for eggs.
If you grow climbing verities on a trellis treatment will be easier.
When I was a kid (1980s Chicagoland) my mother world mail order ladybug and praying mantis eggs and they did a pretty serviceable job at dealing with bugs. Though we did have to hunt down tomato hornworms. We didn't do the diatomaceous earth. Actually I never heard of the stuff until the '00s. We did use ground eggshells to limit slugs.
I do know that with diatomaceous earth you have to make sure to get it all up under the leaves and into the stems, not just dust the leaves a little, and you have to refresh it whenever it rains or is blown away. I think you use a blowy thing, I forget. The YouTuber MI Gardener has a lot of good advice.
Edit: this site has a lot to say on the specific topic of squash bugs, which I've personally not encountered. https://www.almanac.com/pest/squash-bugs