What Is Azalea Leafminer? Nursery Pest Alert!

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May 18, 2016

While visiting eastern NC nurseries last week an insect called the azalea leafminer, Caloptilia azaleella, was mentioned. The next day I receive an email from a county agent requesting a nursery visit to confirm the presence of the same insect. Both instances were on Encore azaleas but this pest attacks all azaleas.

Azalea leafminer damage

Azalea leafminer general damage, Photo by Matt Bertone

Azalea leafminer adult moths emerge about the time of first spring flowering. They overwinter as pupae in rolled leaves or as larvae in mined leaves. Adults are no more than one-half inch long and yellow with purple markings near the base and apex of their forewings. They stand at attention when at rest at a 60 degree angle to the leaf and have antennae the length of their body.

Azalea Leaf Miner Adult Moth

Azalea leafminer adult moth, Photo by Matt Bertone

After mating, adults deposit individual eggs (up to 5) along the mid-vein on the underside of leaves. These should be visible with a hand lens when scouting.

Azalea Leaf Miner Egg, Photo by Matt Bertone

Azalea leafminer egg near center of image on edge of leaf mine, Photo by Matt Bertone

Yellow larvae are caterpillars. They hatch in about 4 days and enter the leaf tissue leaving mines that are light green. Larvae reach one-quarter to one-half inch in length at maturity.

Active mines

Active mines, Photo by Matt Bertone

Early young leaf miner

Early young leafminer with lower leaf epidermis removed, Photo by Matt Bertone

When they get larger the larvae emerge from the leaf and become a leaf tier. Leaf tissue in the abandoned mines dies and turns brown.

Old mine leaf damage

Old leafminer damage, Photo by Matt Bertone

They roll leaf tips downward and feed causing holes and/or browning of tissue.

Larva spinning silk

Larva spinning silk to tie leaf tip down, Photo by Matt Bertone

When larvae reach full size they move to the edge of the leaf and slightly roll it to pupate. Adult moths hatch in about 7 days and the process begins again. There are multiple generations each year in the south.

Cocoon at leaf edge

Cocoon at leaf edge with pupal skin, Photo by Matt Bertone

Adults can may be targeted with contact insecticides like pyrethroids (bifenthrin, cyfluthrin, permethrin). Abamectin (translaminar systemic), azadirachtin (insect growth regulator, botanical, and antifeedant), and spinosad (natural bacterium) will aid in control of larvae at first sign of injury. Systemic products to consider for rotation are acephate (organophosphate) and acetamiprid (the only neonicotinoid with some activity on caterpillars). Since larvae feed in the leaf tissue initially and they roll leaves to protect themselves, they are difficult to control with contact products only. Scout weekly starting at flowering to determine life stage present, need for application, and rotation plan based on insect development. There are some parasitoids that target this pest.

Parasitoid pupa

Parasitoid pupa and leafminer tip damage, Photo by Matt Bertone

More detailed information can be found in the following references used:

NC State Entomology Azalea Leaf Miner Fact Sheet

2016 NC Agricultural Chemicals Manual go to page 156 for leafminers

University of Florida Featured Creatures

University of Georgia

Pacific Northwest Insect Management Handbook

At present in central eastern NC this pest is in it’s 2nd generation as an adult and will be laying eggs, hatching, and leaf mining soon. Inspect azaleas now for adults, signs of leafminers and leaf tiers, and symptoms of damage.

Danny Lauderdale, Area Specialized Agent, Nursery & Greenhouse-Eastern Region. Thanks to Dr. Steve Frank, Extension Entomologist, for editing and review and to Matt Bertone for his excellent images!