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Squash vine borers (SVB's) are one of the worst pests in the garden. Lots of things chew on leaves and we can live with that, but the SVB's can quickly kill a large flourishing plant. If you scroll down below the posts, you will find a section called Similar Topics with a list of a number of previous threads about them. If you read in those, you will find lots of suggestions.
you find them right away, as soon as the larvae hatch out and crawl inside the stem of your plant, you may be able to dig them out with a knife (just make a little slit) and save your plant for the time being. But what they do is start chewing out the inside of the stem. This cuts the circulation channels by which the plant gets water and nutrients from the soil. Once those are gone, there is nothing you can do to repair them or save your plant.
You can try growing your plants under row cover. This has to be done BEFORE the adult moth has laid eggs on your plant and it means pollinators can't get to the flowers, so you will have to hand pollinate. You can try keeping your plant well dusted with diatomaceous earth (has to be re-applied after rain). You can try wrapping the base of the stems where the larvae bore in with something to keep them out. You can be very vigilant watching for their eggs and get rid of them:
they are very small, laid singly at the base of the stem where the larvae that hatch out will bore in.
If from the beginning of the season, you wipe your stems vigorously with a wet cloth to get rid of the eggs, every few days until well into summer, you might be able to stay on top of them
You can inject the stems with Bt or beneficial nematodes, both of which are harmless to anything but the pests.
But honestly, where I was before, I just gave up on trying to grow zucchini. You can grow butternut squash, which don't have the hollow stems and are much more resistant to the SVB.