Hydrangea leaftier caterpillar causes no real damage

Ann Hazelrigg, University of Vermont Extension
Photo by Ann Hazelrigg/University of Vermont Extension. Bladder-like pouches of cupped leaves, tied together with silk, found at the ends of hydrangea branches are a sign of the hydrangea leaftier caterpillar.
Photos by Ann Hazelrigg/University of Vermont Extension Bladder-like pouches of cupped leaves, tied together with silk, found at the ends of hydrangea branches are a sign of the hydrangea leaftier caterpillar.

If you have hydrangeas in your yard, you may have noticed odd structures in the plant in mid-May. These bladder-like pouches at the ends of branches are made up of cupped leaves tied together with silk and are formed by the hydrangea leaftier caterpillar (Olethreutes ferriferana). The hydrangea leaftier is common throughout eastern North America, from Maine to North Carolina.

The small brown and white patterned adult moth emerges in the spring and lays eggs on the ends of hydrangea branches. The white pattern on the moth resembles bird droppings, which protects the moth from predation by birds.

After the eggs hatch in the spring, the small translucent green caterpillars with shiny black heads cement the terminal leaves together with silk thread. The tied leaves stop expanding and become wrinkled.

Photo by Ann Hazelrigg/University of Vermont Extension. Bladder-like pouches of cupped leaves, tied together with silk, found at the ends of hydrangea branches are a sign of the hydrangea leaftier caterpillar.
Bladder-like pouches of cupped leaves, tied together with silk, found at the ends of hydrangea branches are a sign of the hydrangea leaftier caterpillar.

If you pull apart the leaves, you will find a very hungry caterpillar along with little dark green frass pellets. After feeding inside the pouch for a few weeks and growing to about a half an inch, the caterpillar drops to the soil and pupates to emerge as the moth next spring, completing the lifecycle.

The hydrangea leaftier has only one generation per season, so no new leaf nests will appear. Those formed earlier will remain visible for the rest of the season.

This minor pest causes no real damage to the overall health of the bush, so no pesticides are warranted. Plus, the little caterpillars are very protected within their shelter so contact insecticides would be of no use.

You could handpick the structures if they are unsightly or mechanically squish the pest before it pupates. If you see these on your hydrangeas, be sure to quiz your kids to have them guess what is inside and then show them.

(Ann Hazelrigg Hazelrigg is the University of Vermont Extension plant pathologist and director of the Plant Diagnostic Clinic.)