Companion plants are plants that are help other plants grow better, either by providing shade, support or nutrients, or by deterring pests. They can improve productivity and can be an organic way to try to control insect pests. Here are just a few examples.
Help to repel carrot fly, Japanese beetle, and aphids
Helps repel ants, many kinds of beetles and flies, squash bugs, cutworms, Small White, and Cabbage White moths
Helps deters potato beetles