Experts and BHG readers answer.
It sounds as though your potatoes have Colorado potato beetles. This beetle has a rounded light yellowish shell marked with black stripes. Colorado potato beetle is resistant to most chemical controls. It's better to prevent infestations by using appropriate cultural practices. Start by adjusting your planting date. Plant potatoes as early as possible in spring. By the time the beetles attack, the crop will be mature enough to escape significant damage. Use an early-maturing variety and aim for a midsummer harvest. Another option is to wait to plant until early summer. By the time the potatoes emerge, most beetles will be gone. Late-planted potatoes will mature in fall. If you have a small planting, handpicking beetles is an effective control. Inspect plants a couple of times per week and remove all larvae and adult beetles. Place floating row covers over plants to prevent adult beetles from getting to the plants. Bacteria called Bt (Bacillus thuringiensis san diego or Bt tenebrionis) control Colorado potato beetle larvae. These products work slowly; larvae may not die until 4-5 days after treatment. Spray Bt when the larvae are just starting to develop.