Pest profile

Larger Elm Leaf Beetle

Monocesta coryli · Coleoptera: Chrysomelidae[3]

The larger elm leaf beetle is one of the largest leaf beetles in the United States, orange with metallic blue spots; it appears suddenly in large numbers, defoliates elms for a year or two, then disappears for years.[1][2]

Larger elm leaf beetle, orange with metallic blue-green wing covers
Larger elm leaf beetle, orange with metallic blue-green wing covers. (c) jrcagle, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Adults are 3/8 to 5/8 inch long, orange with four dark to metallic blue spots that may merge into two broad bands across the wings.[1][2]
  • Larvae are orange and up to 3/4 inch long, conspicuous and easy to recognize.[1][2]
  • Adults and larvae give off an orange fluid when disturbed.[1]

Look-alikes

Look-alikeHow to tell them apart
Elm leaf beetleA much smaller elm pest, about 1/4 inch, with lengthwise stripes.[2]

Where it lives

It occurs from Pennsylvania south to Florida and west to Kansas, though unevenly, and has spread into Ohio.[2]

US map: public records from 14 states since 1990 (GBIF).

Biology and life cycle

It overwinters as grubs in the soil, pupates in spring, and new adults emerge from April or May.[1][2]

Females lay masses of 24 to 58 eggs in hard, yellow, crusty clusters on leaf undersides; eggs hatch in about two weeks.[1][2]

Young larvae feed in groups for three or four days, then disperse; mature larvae crawl down the tree and wander before burrowing into the soil. There is one generation a year.[1][2]

Damage and signs

  • Elm is the main host; it also feeds on hazelnut, hawthorn, river birch, pecan, dogwood and plum.[1][2]
  • Adults chew holes in leaves, larvae skeletonize them, and spring defoliation harms elms more than late-season feeding.[1]

Health risk

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

Control

Biological control

A tachinid fly and other parasites usually keep it below noticeable levels; outbreaks collapse after a year or two.[1]

Pesticides

If severe defoliation hits early in the season on a small, valued tree, most residential landscape insecticides, including pyrethroids, give adequate control.[1]

Common questions

What are the big orange beetles with blue spots on my elm?
Likely larger elm leaf beetles, among the largest leaf beetles in the US.[1][2]
Should I spray for larger elm leaf beetle?
Only for severe early-season defoliation on a small, important tree; outbreaks usually end on their own.[1]
Why are orange larvae crawling on the ground under my elm?
Mature larvae crawl down and wander before burrowing into the soil to overwinter.[1][2]

Sources

  1. NC State Extension, “Larger Elm Leaf Beetle.” content.ces.ncsu.edu/larger-elm-leaf-beetle (accessed 2026-10-15)
  2. University of Florida IFAS Extension (Featured Creatures), “Larger Elm Leaf Beetle, Monocesta coryli (EENY-180).” ask.ifas.ufl.edu/publication/IN337 (accessed 2026-10-15)
  3. iNaturalist, “Monocesta coryli taxon page (order and family).” www.inaturalist.org/taxa/196775 (accessed 2026-10-06)

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