Once the nymphs start feeding its pretty hard to get a handle on squash bug damage. Early detection is best. A daily check under the leaves for eggs works well. When you find these little clusters scrap them off and dispose of them. You can start to do the math if one adult lays 15 to 20 eggs and they hatch the problem will only get bigger next year. If you do get an infestation that takes down your plant, it is best to pull the plant, bugs and all, and seal it in a garbage bag to send  out with the trash. Most years the squash bugs only have one life cycle, so you can sometimes try a 2nd crop of fast growing zucchini in mid July. 

Nymphs ready to feed on leaves and squash

I can never stress enough how important it is to walk your garden often and watch for signs of insect and pest damage. Stop them early before they get a foothold. Here are some other pests you should be on the lookout for: 

Tomato Hornworm

 Above is the tomato hornworm. You can just pick them off, but if you see one covered with these white eggs, leave it. These are larvae of a parasitic wasp that will kill the worm and create future generations of wasp to keep worms in check.

Colorado Potato Beetle

 Don't be fooled by its name it could just as well be called the Indiana Potato Bug. If you see these, pick them off and put them in a bucket of soapy water. 

Cabbage Butterflies or Moths that lay eggs in Brassicias which hatch into little green worms. Row covers or catching these so they can't lay eggs is critical to a great crop. Or, if you do see damage, pick off  the worms. 

These pests are what we deal with in our garden every year. Your garden may differ. It is good to know what you have and think of doing companion planting to help thwart the invasion. The biggest reason we have infestations is that we plant large patches of the same crop, creating a easy to find buffet for pests. So mix it up a bit!