Updated: Aug 3, 2021
Squash bugs are one of many garden pests that multiply fast if you don't get them under control fast enough.
(squash bug stages from egg to adult)
Squash bugs lay dark brown, oval shaped eggs in small clusters. Usually on the underside of leaves, but they will lay eggs anywhere on your squash plants. The eggs hatch within 10 days. So be sure to check your plant leaves every few days to remove them and stop the next cycle from emerging. They are sap sucking pests that drain the life out of your plants causing them to wilt and turn brown or yellow. The nymphs are small and black, and almost look like spiders. The older nymphs are gray, and when they reach the adult stage, they look very similar to stink bugs but with longer shaped bodies that are as hard as rocks. This suit of armor make it hard for them to kill.
How to prevent squash bugs
Squash bugs don't like the smell of garlic. Most pests don't. You can crush a few cloves of garlic and allow it to ferment in water, then spray it on and around your plants. This will mask the strong smell of your plants. This would have to applied often, especially after it rains.
Cover your plants with mesh early on. Don't give them access to your plants in the first place, and you can keep your plants safe from squash bug damage. However, doing so means you will have to hand pollinate or remove the mesh once flowers begin to open to allow pollinators to do their job. In case a few slip in due to small openings, they're easier to control if covered.
Plant pest deterrent plants around your squash. White radishes, nasturtiums and marigolds are great. Plant them in abundance.
How to get rid of squash bugs
Adult squash bugs are harder to kill because of their hard shell that protects them. You can get a cup of soapy water to knock them into. You can also use something like a clothes pin or tweezers to crush them.
For the eggs, you may be inclined to remove the leaf or stem that the eggs are on, but don't. Buy severing the leaves or stems, you release oils from the plant which can attract more pests. Instead, use masking tape to press onto the eggs and they will stick to the tape. You can also use clothes pins or tweezers to crush the eggs.
Neem oil and or a soapy water mixture works on squash bug nymphs. Dilute 100% cold pressed neem oil and water, peppermint soap and water, or even neem oil AND peppermint soap with water to spray the nymphs and they will die on contact. This is less effective on the adults. It smothers them, but you'll need to give them a good dose. They will crawl away but if you continue spraying, they will eventually die. It best to just use the cup of soapy water or clothes pin method for adult squash bugs.
If you have a squash bug problem that you haven't gotten under control, if possible, try no to plant squash in the same area. The adults can over winter in the soil and emerge in spring to start a new generation. If you stay on top of getting rid of the eggs, you can stop the cycle for the seaon.