The imported willow leaf beetle is a tiny, shiny blue-black beetle that lives on willows and poplars across eastern North America. It was first found in the US in 1915, probably arriving from Europe on nursery plants. Adults and their spotted grubs feed together on the leaves, often leaving them brown, lacy, and ragged by midsummer.
Appearance
- Appearance
- A small, rounded, shiny beetle about 1/8 in (3–4 mm) long, metallic blue to blue-green or nearly black. It looks a lot like a black lady beetle, but it has no spots.
Look-alikes
Black lady beetlesCoccinellidae
Black lady beetles usually have orange spots; the willow leaf beetle is plain shiny blue-black with no spots.
Why they get mixed upBoth are small, round, and shiny.
Where it lives
- Typical habitats
- Stream and pond edges
- Parks
- Yards
- Range
- Native to Europe and Asia. In North America it is common across the eastern half of the US, from Nova Scotia south to the Carolinas, and north into Canada, with scattered reports in the West.
- Preferred conditions
- Wherever willows, poplars, or cottonwoods grow, often near water.
Behavior
- Diet
- Adults and larvae eat willow, poplar, and cottonwood leaves (not tulip poplar). Adults chew holes and notches; young larvae feed in groups and scrape the leaf surface down to a see-through skeleton.
- Activity
- Adults come out in early spring to feed on new leaves. There are usually two or three generations a year in the US, so eggs, larvae, and adults can all be seen at once in summer.
- Overwintering
- Adults spend the winter under loose bark or in leaf litter near their host trees.
Life cycle
- Reproduction
- Females lay clusters of bright yellow, spindle-shaped eggs standing upright on leaf undersides, starting in May.
- Larva
- Larvae are small grubs with a black head and legs and a greenish-yellow body with rows of black bumps, growing to about 1/4 in (5–8 mm). They right on the leaf, attached by the tip of the abdomen.
Cautions
- Cautions
- Harmless to people. The larvae have glands along their sides that give off a strong-smelling substance to put off predators.
Conservation
- IUCN Red List
- NENot EvaluatedNot yet assessed
- Threats
- Heavy feeding can strip a willow and make it look dead, but most trees leaf out again and survive unless it happens year after year. Small or newly planted trees suffer the most.
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