Elm Leaf Beetle
Pyrrhalta aenescens
A small bronze beetle that strips elm crowns bare
The Elm Leaf Beetle is a common small leaf beetle (Chrysomelidae), short-bodied and nearly hemispherical, with a blue-green to bronze metallic sheen. Both adults and larvae feed on elm leaves; larvae skeletonize them, leaving only a lace of veins, and severe infestations can strip a whole tree bare early.
Key figures
- Length
- About 5–7 mm long, yellowish brown to bronze in color, with a metallic sheen
- Life cycle
- In warm regions it can produce 2–3 generations a year, with a short generation time
- Habitat
- Tree crowns and trunks wherever elms grow
- Diet
- Both adults and larvae feed on elm leaves, making it a significant elm pest
- Group pupation
- Mature larvae often crawl together to bark crevices or the base of the trunk to pupate as a group
- Damage
- Severe outbreaks can strip an entire elm tree of its leaves, causing early leaf drop
Life cycle
Egg → Larva (feeds in groups) → Pupa → Adult
Ecological role
Both adult and larval Elm Leaf Beetles feed on elm leaves; severe outbreaks can strip an entire tree bare and stunt its growth, making it a significant pest of urban street trees and shelterbelt forests.
Did you know
Before pupating, mature larvae crawl down the trunk in dense processions and cluster in bark crevices to pupate together; moving as a group lowers the odds that any single larva gets picked off by a predator.
Range
Most elm-growing regions of China, widespread across East Asia
Status
Common, and a significant pest of elms used as urban street trees and in shelterbelt forests
Anatomy
- Elytra — The elytra (wing cases) carry a blue-green to bronze metallic sheen with fine, dense pitting — the source of its Chinese name
- Head — The head is narrow and small, with mouthparts angled forward for gnawing along leaf edges
- Antennae — The thread-like antennae are about half the body length, used to locate fresh elm leaves
- Legs — The feet (tarsi) bear adhesive hairs that grip firmly onto smooth leaf surfaces while feeding
- Pronotum — The pronotum is glossy, similar in color to the elytra
- Compound eyes — The compound eyes are small and prominent, positioned toward the front of the head on either side
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