Knotweed Leaf Beetle

Gastrophysa polygoni · Order: Coleoptera · Family: Chrysomelidae

Also called: Knotwood Leaf Beetle

No source yet on danger. We have no source yet on whether it bites, stings or damages anything.
Knotweed Leaf Beetle
Photo: katunchik, CC BY

The knotweed leaf beetle grows up to about 5 mm long. It is green-blue with an orange thorax and metallic-green wing cases. Adults are visible during the spring and summer months.

Source: Wikipedia

Size

It can reach a length of up to 5 mm.

Source: Wikipedia

When you see it

You can see this beetle in spring and summer.

Source: Wikipedia

Where it is found in the US

Recorded in 27 of 51 states and DC. Most records: Pennsylvania, Nebraska, Michigan, Minnesota, Wisconsin, New York, South Dakota, Massachusetts.

Darker = more records. Counts are museum and citizen-science records, not population size.

Source: GBIF

Status: introduced in North America; introduced in Canada; introduced in United States. Source: iNaturalist

Months it is reported in the US

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Source: GBIF

More photos

Knotweed Leaf Beetle photo 3
Photo: Barry Walter, CC BY
Knotweed Leaf Beetle photo 4
Photo: Steve DeGrace, CC BY
Knotweed Leaf Beetle photo 5
Photo: unknown, CC0
Knotweed Leaf Beetle photo 6
Photo: booksandcookies, CC BY-SA

Same family (Chrysomelidae)

Spotted Cucumber BeetleSpotted Cucumber BeetleDiabrotica undecimpunctataDamages trees, gardens or cropsBean WeevilBean WeevilAcanthoscelides obtectusDamages trees, gardens or cropsCowpea WeevilCowpea WeevilCallosobruchus maculatusDamages trees, gardens or cropsSwamp Milkweed Leaf BeetleSwamp Milkweed Leaf BeetleLabidomera clivicollisDamages trees, gardens or cropsAlder Leaf BeetleAlder Leaf BeetleAgelastica alniDamages trees, gardens or cropsDogbane Leaf BeetleDogbane Leaf BeetleChrysochus auratus

Sources

  • Wikipedia: https://en.wikipedia.org/wiki/Gastrophysa_polygoni

Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia

Text written 2026-10-22 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-22.

How this page works

This is one bug's fact sheet. The colored box at the top says whether it is dangerous. Sections below cover how to recognize it, whether it is a pest, and how to deal with it. The US map shows which states have records; tap a state to see other bugs there.

Every fact on Bug FAQ comes from a named source (university extension sites, government agencies, GBIF, iNaturalist, Wikipedia). The source is linked next to each section. If we have no source for something, we leave it out.