Pest profile

Navel Orangeworm

Amyelois transitella · Lepidoptera: Pyralidae[2]

Navel orangeworm larvae fill almonds, walnuts, pistachios, figs and pomegranates with webbing and frass, and old leftover nuts are where they overwinter.[1]

Navel orangeworm moth, a mottled black, gray and white moth with a snoutlike head, resting on a pale surface
Navel orangeworm moth, a mottled black, gray and white moth with a snoutlike head, resting on a pale surface. (c) Mary Beth Stowe, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Larvae are reddish orange when young and later cream colored, with a dark crescent on each side of the second segment behind the head.[1]
  • Last instars are up to 3/4 inch long.[1]
  • Adults are mottled black and gray moths about 2/3 inch long with a snoutlike head.[1]

Where it lives

It attacks almond, pistachio, walnut, fig and pomegranate; in warm years the central and southern San Joaquin Valley can see a fourth generation.[1]

US map: public records from 8 states since 1990 (GBIF).

Biology and life cycle

Larvae overwinter in old nuts and fruit (mummies) and keep feeding on warm winter days.[1]

Moths emerge in March or April and lay eggs on mummies, then on new nuts after hull split or on injured fruit.[1]

There are at least three generations a year, sometimes four in warm seasons.[1]

Damage and signs

  • Pinhole entrances lead to whole kernels eaten, with webbing, frass and mold.[1]

Health risk

It feeds in nuts and fruit; UC IPM mentions no risk to people.[1]

Control

Prevention

Harvest early, avoid drought stress that splits hulls early, and prevent other injury to fruit.[1]

Sanitation

Knock down and dispose of old nuts and fruit before late winter; this is the most effective control.[1]

Biological control

Parasitic wasps, including commercially available Goniozus legneri, and egg-eating Phytocoris bugs help; avoid broad persistent sprays.[1]

Common questions

What's the webbing and frass inside my walnuts?
Navel orangeworm larvae leave webbing, frass and mold inside nuts.[1]
Why remove old nuts from the tree?
Mummies are the main source of spring moths, so removing them is the most important control.[1]

Sources

  1. University of California Statewide IPM Program, “Navel Orangeworm (Pests in Gardens and Landscapes).” ipm.ucanr.edu/PMG/GARDEN/FRUIT/PESTS/navelorwrm.html (accessed 2026-10-06)
  2. iNaturalist, “Amyelois transitella taxon page (order and family).” www.inaturalist.org/taxa/347144 (accessed 2026-10-06)

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