Pest profile

Imported Willow Leaf Beetle

Plagiodera versicolora · Coleoptera: Chrysomelidae[3]

The imported willow leaf beetle is a small, shiny blue-black to greenish beetle that looks like a black lady beetle; adults and larvae skeletonize willow, poplar and cottonwood leaves through the summer.[1][2]

Imported willow leaf beetle, a small shiny metallic green-blue beetle, on a leaf
Imported willow leaf beetle, a small shiny metallic green-blue beetle, on a leaf. (c) Nash Turley, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Adults are about 3/16 inch long, convex and oval, nearly black to metallic greenish blue.[2]
  • They resemble an all-black lady beetle, but lady beetles are in a different family and black ones usually have orange spots.[1]
  • Larvae are small and dark, up to about 1/4 inch, and feed in groups on leaf undersides.[1][2]

Where it lives

It was first detected in the United States in 1911; UMass notes there may be four generations a year in parts of Virginia and North Carolina.[2]

US map: public records from 25 states since 1990 (GBIF).

Biology and life cycle

Adults overwinter in loose bark or other sheltered spots near the tree and emerge in spring shortly after leaves open.[1][2]

Females lay tiny yellow eggs in clusters on leaf undersides; larvae hatch in a few days and skeletonize leaves, pupating after three to four weeks.[1][2]

At least two generations occur each year, so all stages can be found together.[1]

Damage and signs

  • Hosts are willows, cottonwood and poplars (not tulip poplar).[1][2]
  • Adults notch and chew holes in leaves and larvae skeletonize them; infested trees gradually turn off-color and may look dead from a distance.[1]
  • Complete defoliation isn't fatal to a willow, but it isn't good for it.[1]

Health risk

None to people or pets.[1][2]

Control

Prevention

Keep pyrethroids away from pools, ponds and streams, since they are very toxic to fish.[1]

Pesticides

Treatments may seem to fail because eggs survive and hatch afterward and beetles don't all leave their winter shelters on the same day; NC State lists several landscape insecticides labeled for leaf beetles.[1]

Common questions

What are the small shiny blue beetles on my willow?
Likely imported willow leaf beetles; their larvae skeletonize the leaves.[1][2]
Are they black lady beetles?
No. They resemble black lady beetles but belong to a different family, and black lady beetles usually have orange spots.[1]
Why do the beetles come back after spraying?
Eggs may survive and hatch later, and adults leave their winter shelters over several days.[1]

Sources

  1. NC State Extension, “Imported Willow Leaf Beetle (PDIC Factsheet).” content.ces.ncsu.edu/imported-willow-leaf-beetle (accessed 2026-10-15)
  2. UMass Extension Landscape, Nursery and Urban Forestry Program (Landscape Insect & Mite Guide), “Plagiodera versicolora (Imported Willow Leaf Beetle).” www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/plagiodera-versicolora (accessed 2026-10-15)
  3. iNaturalist, “Plagiodera versicolora taxon page (order and family).” www.inaturalist.org/taxa/83839 (accessed 2026-10-06)

Updated 2026-10-15. Built from sourced records. Spot an error? Tell us.