Find the eggs
Squash bugs lay eggs on the undersides of leaves in evenly spaced groups.
Get in the habit of scouting your squash plants for the shiny, yellowish brown to reddish eggs.
Also, keep your eyes peeled for the small, light gray or green, wingless squash-bug nymphs, which suck on the plant's sap, causing the leaves to wilt, blacken, and die.