Pest profile

Threelined Potato Beetle

Lema daturaphila · Coleoptera: Chrysomelidae[2]

Threelined potato beetles rarely matter on potatoes, but on tomatillos their frass-covered larvae can strip plants.[1]

Threelined potato beetle, a small yellowish beetle with three black stripes and an orange thorax, on a leaf
Threelined potato beetle, a small yellowish beetle with three black stripes and an orange thorax, on a leaf. Photo: Jesse Rorabaugh, public domain (CC0), via iNaturalist

How to identify it

  • Adults are a little over 1/4 inch with cream to reddish-yellow wing covers bearing three black stripes.[1]
  • The reddish-orange area behind the head has two small black dots.[1]
  • Larvae are green with shiny black heads and cover themselves with their own feces.[1]

Look-alikes

Look-alikeHow to tell them apart
Striped cucumber beetleLooks similar, but the two feed on different plants.[1]

Where it lives

It's active May through August in Minnesota and usually found in low numbers.[1]

US map: public records from 37 states since 1990 (GBIF).

Biology and life cycle

Females lay clusters of orange eggs under leaves; most new adults emerge in August.[1]

It likely overwinters in the soil, and it's unclear whether there are one or two generations.[1]

Damage and signs

  • Adults and larvae eat leaves of tomatillos, potatoes, tomatoes and other nightshades; larvae can badly defoliate tomatillos.[1]

Health risk

It feeds on plants; Minnesota Extension mentions no risk to people.[1]

Control

Keep them out

Row covers work if you rotate away from last year's nightshades and cover before beetles arrive.[1]

Sanitation

Remove nightshade weeds such as ground cherry.[1]

Traps and physical control

Handpick beetles and larvae into soapy water and squash egg clusters.[1]

Common questions

What are the slimy brown larvae on my tomatillos?
Likely threelined potato beetle larvae, which cover themselves with their feces.[1]
Do they hurt potatoes?
Rarely; they're mainly a problem on tomatillos.[1]

Sources

  1. University of Minnesota Extension, “Three-lined potato beetles (Yard and garden insects).” extension.umn.edu/garden-and-home/yard-and-garden/yard-and-garden-insects/threelined-potato-beetles (accessed 2026-10-06)
  2. iNaturalist, “Lema daturaphila taxon page (order and family).” www.inaturalist.org/taxa/203403 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.