Pest profile

Elm Zigzag Sawfly

Aproceros leucopoda · Hymenoptera: Argidae[2]

Elm zigzag sawfly is an invasive East Asian pest that defoliates elms, first found in the US in Virginia in 2021.[1]

Elm zigzag sawfly damage, a zigzag feeding track cut into an elm leaf
Elm zigzag sawfly damage, a zigzag feeding track cut into an elm leaf. (c) carnifex, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Young larvae chew a distinctive zigzag pattern into elm leaves; older larvae eat broader areas.[1]
  • Larvae turn green with a black head band and T-shaped black marks on two pairs of legs, reaching 10 to 11 mm.[1]
  • Adults are small shiny black wasp-like flies, 7 to 8 mm, with smoky wings and yellow legs.[1]

Where it lives

It reached Québec in 2020 and Virginia in 2021; HGIC covers it for South Carolina elms.[1]

US map: public records from 11 states since 1990 (GBIF).

Biology and life cycle

No male has ever been found: females reproduce alone, each laying up to 60 eggs during a 1 to 6 day life.[1]

Larvae feed for 15 to 18 days; two to five generations a year have been seen in the US.[1]

Damage and signs

  • Large infestations can defoliate whole trees, and defoliation can weaken them.[1]
  • It feeds on American, winged, slippery, Siberian, Chinese and English elms, apparently favoring non-native elms.[1]

Health risk

It feeds on plants; Clemson HGIC mentions no risk to people.[1]

Control

Prevention

Monitor elms; if you suspect it, capture or photograph the insect and report it to Clemson Extension or Clemson DPI.[1]

Pesticides

Little is known about control; systemic insecticides show promise in ongoing research.[1]

Common questions

What's making zigzag holes in my elm leaves?
The zigzag feeding pattern is the hallmark of elm zigzag sawfly larvae.[1]
Should I report elm zigzag sawfly?
Yes; HGIC asks South Carolinians to report suspected insects to Clemson Extension or DPI.[1]

Sources

  1. Clemson Cooperative Extension, Home & Garden Information Center, “Elm Zigzag Sawfly (HGIC 2026).” hgic.clemson.edu/factsheet/elm-zigzag-sawfly/ (accessed 2026-10-06)
  2. iNaturalist, “Aproceros leucopoda taxon page (order and family).” www.inaturalist.org/taxa/497733 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.