PK-L08 · Yard, turf, and garden pests

How to get rid of Spongy moths

Lymantria dispar

Also called: gypsy moth (former common name)

Spongy moth caterpillars can strip oaks in outbreak years. Egg masses are tan and spongy on bark, outdoor furniture, and vehicles — which is how they hitchhike. The Entomological Society of America adopted “spongy moth” to replace a slur-based common name; you will still see the old name in older PDFs. Homeowners: scrape egg masses into soapy water (PPE — hairs can irritate), follow state quarantine on moving firewood and outdoor gear, and let agencies run aerial Bt programs when they do. Do not invent a backyard chemical program for a regional outbreak.

Spongy moth (Lymantria dispar) — identification photo
Identification photo of Spongy moth (Lymantria dispar). Use this with the notes below — size, color, and markings matter more than a single photo, and look-alikes are listed in the sidebar.

How to identify Spongy moth

  • Caterpillars with paired spots (blue then red down the back in later instars), hairy, on oaks.
  • Tan spongy egg masses on hard surfaces. Male moths fly; females of European strain are heavy and flight-limited.

Signs of an infestation

  • Oaks defoliated in June. Frass raining from canopies.
  • Egg masses on a trailer you are about to drive out of the quarantine.

Biology and why they show up

Invasive. Outbreak cycles. Spread by people moving objects with egg masses. Asian strains have different female flight — regulatory concern.

Health and property risk

Tree stress (especially repeated defoliation plus drought), skin irritation from hairs, quarantine violations. Not a house moth in the pantry sense.

Proven control sequence

Work in this order. Skipping inspection or exclusion is why most “treatments” bounce back in a week.

  1. Scrape egg masses into soapy water. Wear gloves and eye protection. Destroy, do not toss into the next county.
  2. Obey quarantine on firewood and outdoor household items. Inspect the RV. This is how new counties get them.
  3. Let official programs run when announced. Btk aerial treatments are agency tools with public notice. Home foggers are not a forest program.

Prevention that actually sticks

  • Buy local firewood. Inspect outdoor furniture before interstate moves.
  • Keep oaks as healthy as you can; a stressed tree plus defoliation goes badly.

When to hire a licensed professional

Arborists for high-value trees, agencies for outbreaks. Homeowners: egg masses and quarantine hygiene.

Legal and safety notes. State and federal quarantines. The common-name change does not change the law. Do not move infested material.

United States and Tier 1 notes

Northeast US core, expanding. Canada similar. Europe has L. dispar with different cultural status. Not a California native oak moth (different insect) — ID matters on the West Coast.

Common questions

Why did the name change?

ESA replaced a slur-derived name. The insect and the quarantines are the same. Search older literature under both names.

Sources

Written by the Pest Kill Editorial Team. Published August 25, 2026. Last reviewed September 13, 2026.