Colorful caterpillars capable of completely defoliating shrubs spotted across the region
By Jessica Strickland, Wayne County Horticulture Extension Agent
WAYNE COUNTY, N.C. — Local gardeners are being urged to inspect their azalea plants for destructive caterpillars that typically emerge in late August and early September, earning them the nickname “Labor Day worms.”
Identifying the Azalea Caterpillar Threat
The azalea caterpillar, a colorful pest that can severely damage popular landscape shrubs, has begun appearing on azaleas throughout Wayne County. These distinctive caterpillars are easily recognizable by their striking appearance and defensive behavior.
“When a caterpillar is disturbed, it will raise its head and tail to curl backwards in defense,” explained Jessica Strickland, Wayne County Horticulture Extension Agent.
The caterpillars undergo dramatic color changes as they mature. Young specimens appear as small, green caterpillars that develop into purple and yellow-striped insects. In their final stage, they become large black and yellow-striped worms with distinctive red heads and legs.
Life Cycle and Damage Patterns
The azalea caterpillar’s destructive cycle begins in early summer when adult moths deposit large egg masses containing 80 to 100 eggs on the undersides of azalea leaves. These eggs hatch into the problematic caterpillars that cause significant damage from late August through September.
The pests feed in groups, making early detection challenging. “Because the caterpillars feed in groups, they are often not detected until a portion of an azalea is severely defoliated,” Strickland noted. The caterpillars can completely strip leaves from entire branches, leaving azalea shrubs severely damaged.
Control and Prevention Strategies
Extension officials recommend several approaches for managing azalea caterpillar infestations, ranging from manual removal to targeted treatments.
Manual Control Methods
For small infestations, gardeners can physically remove caterpillars by hand—they pose no danger to humans—and dispose of them in soapy water. Alternatively, caterpillars can be shaken from shrubs and eliminated manually.
Biological Controls
For those preferring organic solutions, Bacillus thuringiensis (B.t.), commonly marketed under the brand name DiPel, provides effective control of young caterpillars.
Chemical Treatments
When infestations are severe, several insecticides offer adequate control, including Sevin (carbaryl), Orthene (acephate), and pyrethrin-based products. Extension experts emphasize that timing is crucial for effective treatment.
“The best control is achieved by applying when caterpillars are first noticed,” Strickland advised. “Only spray an insecticide if you discover azalea caterpillars on your azaleas.”
Expert Recommendations
Extension officials stress the importance of early detection and targeted treatment. Unnecessary pesticide applications waste both time and money while potentially impacting beneficial insects.
“As you are working in your landscape this time of year, take the time to do some scouting for the azalea caterpillars that could be lurking in your azaleas,” Strickland recommended. “Catching these Labor Day worms early can allow for better control and prevent defoliated azaleas.”
All pesticide users are reminded to carefully read and follow label directions, as regulations and product formulations may change.
Jessica Strickland serves as Agriculture Extension Agent specializing in horticulture for North Carolina Cooperative Extension in Wayne County. For more gardening information, residents can sign up for the Wayne County Extension Gardening email list at https://wayne.ces.ncsu.edu/email-me or visit the North Carolina Extension Gardener Plant Toolbox at https://plants.ces.ncsu.edu.
Disclaimer: Pesticide recommendations are provided for reader convenience. Brand name usage does not constitute endorsement by North Carolina Cooperative Extension. Users are responsible for ensuring compliance with current regulations and product labels.
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