Hydrangea Leaftier Oddball Damage

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I first came across the odd looking handiwork of Hydrangea Leaftier Moth (Family Tortricidae; Olethreutes ferriferana) caterpillars several years ago on its native namesake host in Clifton Gorge in Greene County, OH.  Since that time, I've commonly found this leaftier on wild and cultivated hydrangeas at other locations.

 

Hydrangea Leaftier

 

Individual caterpillars apply silk along the edges of two newly expanding hydrangea leaves to cement or tie the leaves together.  This creates a purse or envelope-like structure that surrounds both newly developing leaves and flowers.  The caterpillars then feed upon the leaves and flowers enveloped within these protective structures.   The leaf structures created by this leaf-tier caterpillar tend to occur near the tips of plant stems and may be very obvious. 

 

Hydrangea Leaftier

 

Hydrangea Leaftier

 

The two tied leaves fail to fully expand and become dark green, wrinkled and gnarled; the structure may superficially resemble a plant gall.  Opening the tied leaves will reveal the caterpillars housed within silk littered with dark green frass pellets.  The light green semi-transparent caterpillars have shiny black head capsules and a black thoracic shield on top of the segment just behind the head.

 

Hydrangea Leaftier

 

Published records indicate that high populations may occasionally cause significant damage; however, it's more common for the caterpillars to be viewed only as an oddity affecting plant aesthetics.  Caterpillars may be eliminated if control is deemed necessary by squeezing the leaf structures to mash the caterpillars.  The leaf structures shield the caterpillars from direct exposure to a topical insecticide and there is no data on the efficacy of systemic insecticides.