PestControlBasics
Menu

Identify

Treat

Local

About

Southern Purple Mint Moth

Pyrausta laticlavia[3]

The southern purple mint moth is a small native moth whose caterpillars, called rosemary webworms, web together and kill the foliage of rosemary.[1][2]

Group
Insect
Order
Lepidoptera
Family
Crambidae
US records
21 states
Sources
3 cited
Updated
2026-10-16
Southern purple mint moth with pink and yellow banded wings on a plant
Southern purple mint moth with pink and yellow banded wings on a plant. (c) John P Friel, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0
On this page
  1. Identification
  2. Look-alikes
  3. Where it lives
  4. Biology
  5. Damage and signs
  6. Health risk
  7. Control
  8. Common questions
  9. Sources

How to identify it

  • Moths have a wingspan of about 3/4 inch, with reddish-purple to pinkish wings marked with yellow bands; they sit in a triangular shape.[1][2]
  • Caterpillars are small and slender, pale brown to green, with rows of black spots down the back and sides.[1][2]
  • Infestations show as masses of dead leaves held together by webbing studded with frass pellets, often on the upper parts of branches.[1][2]

Look-alikes

Look-alikeHow to tell them apart
Spider webbingClemson notes spider webs are sometimes mistaken for an early infestation; look for the spotted caterpillars.[2]

Where it lives

Native to the Southeast; Clemson reports it on rosemary throughout the Charleston, South Carolina, area for over 10 years.[1][2]

US map: public records from 21 states since 1990 (GBIF).

Biology and life cycle

Little has been published on its biology; the caterpillars spin loose webbing as they feed, and frass collects in it.[1][2]

Damage and signs

  • It can damage the foliage on over half of a rosemary plant and likely leads to its decline and death if not managed.[2]
  • NC State describes the caterpillars as damaging to rosemary.[1]

Health risk

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

Control

Traps and physical control

Prune away and dispose of infested, webbed branches.[2]

Pesticides

Spray Bacillus thuringiensis (Bt) products labeled for caterpillars; they kill only caterpillars but may need several applications.[2]

Common questions

What is the webbing and frass on my rosemary?
Often the work of southern purple mint moth caterpillars.[1][2]
Is Bt safe for my herb garden?
Bt products selectively kill caterpillars; use one labeled for caterpillars and follow the label.[2]

Sources

  1. NC State Extension, “Southern Purple Mint Moth (PDIC Factsheet).” content.ces.ncsu.edu/southern-purple-mint-moth (accessed 2026-10-16)
  2. Clemson Cooperative Extension Home & Garden Information Center, “Question of the Week: Southern Purple Mint Moth.” hgic.clemson.edu/question-of-the-week-southern-purple-mint-moth/ (accessed 2026-10-16)
  3. iNaturalist, “Pyrausta laticlavia taxon page (order and family).” www.inaturalist.org/taxa/204081 (accessed 2026-10-06)

Updated 2026-10-16. Built from sourced records. Spot an error? Tell us.