Answer: Usually it's Colorado potato beetle that attacks potatoes in the manner you mention. The humpbacked black-spotted larvae can be reddish to yellow-brown, like you've described. Once they get a toehold in your potato patch, it's really hard to control them. Next year, as soon as the potato plants emerge through the soil, check the undersides of the leaves for masses of orangey-yellow eggs, and squish whatever you find. The adults are yellow and black striped beetles which are easy to catch and squish. Mulch with several inches of old hay or straw, since this makes it hard for the adults to walk to the plants. If all this fails, and the number of larvae starts to grow, use Bt var. San Diego, which is a microbial disease that attacks only Colorado potato beetle. It works best on the very young larvae, and becomes less effective as they mature.
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