Threelined potato beetle
Published in Yard & Garden Line News, September 1, 2003
You may occasionally encounter an uncommon beetle in your garden. The threelined potato beetle is a little larger than 1/4 inch long, with cream colored to reddish yellow wing covers with three black stripes running down its back. It has a reddish orange prothorax (the area behind the head) with two small black dots on it. A threelined potato beetle can be confused with a striped cucumber although these two insects feed on different plants.
It is believed that threelined potato beetles overwinter as adults. In the spring and early summer, they move to host plants to feed on leaves and lay eggs. This beetle loves to eat tomatillos as well as potatoes and other plants in the nightshade family. Once larvae hatch, they also feed on foliage. The larvae have the odd habit of protecting themselves by cementing their own excrement on their back (don't try this at home!). Larvae probably pupate in mid to late summer with most adults emerging in August. It is unclear whether this insect has one or two generations per year.
Fortunately, threelined potato beetles are usually not a problem, although they can be numerous in localized areas. If you encounter theses beetles in your garden, just handpick them and throw them into a pail of soap water. In cases, when an pesticide is justified, use a garden insecticide, such as permethrin or esfenvalerate to reduce their numbers.