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Description and Biology

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Young azalea caterpillars, Datana major, are small green worms that grow into medium purple worms and then into large black- and yellow-striped worms with reddish heads and prolegs. They are sometimes called "Labor Day" worms, because so many folks discover them around Labor Day. Azalea caterpillars are gregarious. When disturbed, the caterpillars often raise their heads and tails so the body is C-shaped. There is only one generation per year. When fully grown, the caterpillars crawl down and burrow into the soil to pupate. There they spent the winter and spring. The moths emerge in early summer and deposit their eggs in masses of 80 to 100 on a leaf. The brownish moths have darker lines across the forewings and a cinamon colored thorax. They belong to a group of moths called handmaid moths, perhaps because these moths are so attractive.

Azalea caterpillar moths fly primarily at night.

Azalea caterpillar moths fly primarily at night.

Azalea caterpillar moths are in a group of handmaid moths.

Azalea caterpillar moths are in a group of handmaid moths.

Eggs are laid in masses.

Eggs are laid in masses.

Young azalea caterpillars are small and greenish.

Young azalea caterpillars are small and greenish.

Mature azalea caterpillars are black with yellow spots.

Mature azalea caterpillars are black with yellow spots.

Azalea caterpillars raise their haids and tails when disturbed.

Azalea caterpillars raise their haids and tails when disturbed.

Azalea caterpillars pupate in the soil.

Azalea caterpillars pupate in the soil.

Host Plants

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Azaleas are the primary host for the azalea caterpillar, but these caterpillars have been found on blueberry, Andromeda, apple, and even oak. As the worms mature, they do more and more damage. Most of the damage occurs in August and September. Because the worms feed in groups, they often completely defoliate a portion of a shrub before they are detected.

Residential Recommendation

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Azalea caterpillars are gregarious, which makes their control relatively easy. They can be shaken from the shrub and trampled underfoot. Sevin, Orthene, and pyrethrin or pyrethroid-based insecticides should give adequate control as well.

References

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For assistance with a specific problem, contact your local Cooperative Extension Center

This Factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology and Plant Pathology

Publication date: June 22, 2013
Revised: Aug. 29, 2019

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