Pest profile

Boxelder Twig Borer

Proteoteras willingana · Lepidoptera: Tortricidae[2]

Boxelder twig borers destroy buds and new shoots of boxelder and red maple, so trees grow bushy and lose their shape.[1]

Boxelder twig borer moth, a small mottled gray moth, on pavement
Boxelder twig borer moth, a small mottled gray moth, on pavement. (c) Steven Joyner, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • The caterpillar is small and whitish yellow with a dark head.[1]
  • Damaged shoots swell, with waste pellets around a small entry hole.[1]

Where it lives

UK Extension describes it on boxelder and red maple.[1]

US map: public records from 12 states since 1990 (GBIF).

Biology and life cycle

Eggs hatch in mid-July and young larvae feed on leaves under silk; in autumn they bore into petioles or buds for winter.[1]

In spring each caterpillar bores into a new shoot to finish developing.[1]

Damage and signs

  • By the time symptoms show, caterpillars are inside twigs and safe from control.[1]

Health risk

It feeds on plants; UK Extension mentions no risk to people.[1]

Control

Pesticides

Control must target the leaf-feeding stage in mid-July; carbaryl applied in late July and again in early August reduces infestations.[1]

Common questions

Why is my boxelder getting bushy?
Boxelder twig borers killing buds and shoots make trees bushy.[1]
Can I treat damaged twigs?
No; larvae inside twigs aren't reachable. Treat the leaf-feeding stage in midsummer.[1]

Sources

  1. University of Kentucky Entomology (ENTFACT), “Boxelder Twig Borer (ENTFACT-415).” entomology.mgcafe.uky.edu/ef415 (accessed 2026-10-06)
  2. iNaturalist, “Proteoteras willingana taxon page (order and family).” www.inaturalist.org/taxa/417016 (accessed 2026-10-06)

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