As the name suggests, the Colorado potato beetle (also known as the potato bug) can do a real number on your potato plants, and when they're done there they'll move on to related plants like tomatoes, peppers or eggplant. Adult beetles lay eggs on the underside of leaves, and then when the larvae hatch they immediately begin eating and can quickly defoliate an entire potato plant. Manually killing or removing them from your potatoes and other garden plants is your best option.
Learn to correctly identify the Colorado potato beetle. Adults have an oval, rounded body like ladybugs, are 1/2 inch long and 3/8 inch wide and have black and orange or yellow running lengthwise down their back. Larvae are smaller, soft-bodied and mostly reddish orange with black spots on the side. Colorado potato beetle eggs are bright yellow-orange and often found on the underside of leaves in clusters of 10 to 30.
Squish any egg clusters you find. Wear gardening gloves if desired, as the eggs might impart a stain or odor to your fingertips.
Remove any adults or larvae by hand and drop them into a jar filled with rubbing alcohol or soapy water to kill them. One tbsp. of liquid soap to 1 quart of water is sufficient. Bury the bodies away from your garden, or otherwise dispose of them.
Consider applying a natural insecticide, such as pyrethrin or neem (azadirachtin). According to the University of Minnesota Extension Office, these plant-derived insecticides are more effective than chemical pesticides, which the Colorado potato beetle is often immune or resistant to. Natural or organic insecticides can be found at many garden centers or online. Always follow package instructions to the letter whenever using insecticides, even natural ones.
Remove and burn any brush or residue from potato, tomato, eggplant and pepper plants at the end of the growing season, to prevent the Colorado potato beetle from overwintering in your garden. Colorado potato beetles will also eat weeds like bittersweet nightshade or ground cherry, so these should be removed, too.