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How to identify it
- Grown caterpillars are about 2 inches long, nearly black with broken white or yellow stripes along the body and a red head and legs.[2][1]
- When disturbed they lift both ends, bending the body into a C shape.[1][2]
- NC State says they are sometimes called Labor Day worms because so many people find them around Labor Day.[1]
- The adult is a brownish, night-flying moth with darker lines across the forewings and a cinnamon-colored thorax, one of the hand-maid moths.[1]
- Eggs are laid in masses of 80 to 100 on a leaf.[1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Yellownecked caterpillar | A close relative in the same genus. BAMONA says the moths are nearly identical, so the host plant is a useful clue: NC State calls azaleas the azalea caterpillar's primary host.[3][1] |
Where it lives
BAMONA gives the range as Nova Scotia to Florida, west to Kansas and Arkansas. Clemson counts it among the main pests of azaleas and rhododendrons in South Carolina.[3][2]
Biology and life cycle
There is one generation a year. Grown caterpillars crawl down and burrow into the soil to pupate, spend the winter and spring there, and the moths emerge in early summer to lay eggs.[1]
BAMONA gives the moth's flight season as June to August.[3]
The caterpillars stay together as they feed and do more and more damage as they grow.[1][2]
Damage and signs
- Because they feed in groups, they often strip part of a shrub before anyone notices.[1][2]
- Most damage happens in late summer, mainly August and September.[1][2]
- Azaleas are the main host. NC State has also found them on blueberry, andromeda, apple and even oak, and BAMONA lists azalea and bog rosemary.[1][3]
Health risk
Clemson says the caterpillars are harmless to people, which makes picking them off by hand practical.[2]
Control
Prevention
Inspect azaleas regularly in late summer for groups of young caterpillars, and act as soon as you find them.[2]
Traps and physical control
Because they cluster, they are easy to deal with by hand: pick them off, or shake them from the shrub and step on them.[2][1]
Pesticides
If spraying is needed, Clemson says Bacillus thuringiensis (Bt) and spinosad work best on small, young caterpillars and lists contact insecticides such as bifenthrin, cyfluthrin, cyhalothrin and permethrin for large ones. NC State warns that pyrethroids are very toxic to fish, so keep them away from pools, ponds and streams. Follow the label.[2][1]
Where sources disagree
Young caterpillars: NC State describes them as small and green, turning purple before the black-and-yellow final stage, while Clemson describes caterpillars about 3/8 inch long as reddish- to brownish-black with white and yellow stripes.[1][2]
Host plants: BAMONA lists only azalea and bog rosemary; NC State adds blueberry, andromeda, apple and oak.[3][1]
Common questions
- What are the black and yellow striped caterpillars on my azaleas?
- Most likely azalea caterpillars, which feed in groups in late summer and have red heads and legs.[1][2]
- Why do they raise their heads and tails?
- That's how they react when disturbed, curling into a C shape.[1][2]
- Can I pick them off by hand?
- Yes. Clemson calls them harmless to people, and since they feed in clusters, removing or shaking off a group takes care of much of the problem.[2][1]
Sources
- NC State Extension, “Azalea Caterpillar.” content.ces.ncsu.edu/azalea-caterpillar (accessed 2026-11-11)
- Clemson Cooperative Extension Home & Garden Information Center, “Azalea and Rhododendron Insect Pests in South Carolina (HGIC 2051).” hgic.clemson.edu/factsheet/azalea-rhododendron-insect-pests/ (accessed 2026-11-11)
- Butterflies and Moths of North America (BAMONA), “Major Datana, Datana major (species account).” www.butterfliesandmoths.org/species/Datana-major (accessed 2026-11-11)
- iNaturalist, “Datana major taxon page (order and family).” www.inaturalist.org/taxa/1191137 (accessed 2026-11-11)