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Threelined potato beetles

Quick facts 

  • This beetle feeds on tomatillos as well as potatoes and other plants in the nightshade family.
  • It is active from May through August.
  • This beetle is usually found in low numbers and is NOT considered a pest.

How to identify three-lined potato beetles

A yellowish beetle with a red head and three black lines down its back seen on a green leaf
Threelined potato beetle on a leaf
A whitish beetle with a red head and three black lines running down the wing covers
Threelined potato beetle

A threelined potato beetle can be confused with a striped cucumber but these two insects feed on different plants.

  • The threelined potato beetle is a little larger than 1/4 inch long.
  • It has 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.

Behavior and habits of threelined potato beetles

Threelined potato beetles live through the winter as adults.

  • In the spring and early summer, they move to host plants to feed on leaves and lay eggs.

  • Once larvae hatch, they also feed on foliage.

The larvae protect themselves by cementing their own excrement on their back.

  • Larvae transform into pupae in mid to late summer, with most adults emerging in August.

  • It is unclear whether this insect has one or two generations per year.

Do you need to control threelined potato beetles

Threelined potato beetles are usually NOT a problem, even if you see large numbers in certain areas.

If you find these beetles in your garden and want to get rid of them:

  • Handpick them and throw them into a pail of soap water.

  • If a pesticide is required, use permethrin or esfenvalerate to reduce their numbers.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

Be sure that the fruit/vegetable you wish to treat is listed on the label of the pesticide you intend to use. Also be sure to observe the number of days between pesticide application and when you can harvest your crop.

Jeffrey Hahn, Extension entomologist

Reviewed in 2018

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