The way to deal with hydrangea leaftier infestations inflicting rolled-up leaves

“My Annabelle hydrangeas have some leaves that look like rolled up. I’m seeing extra this 12 months than in previous years. Is that this one thing that must be handled?”

— Simon Becker, Riverwoods

Your hydrangeas, like these in different gardens across the North Shore, have hydrangea leaftier (Olethreutes ferriferana) current. The injury attributable to this insect seems as as much as 4 leaves tied along with silk on the finish of a department or prime of the plant.

My hydrangeas at house have some cupped single leaves on the prime of the crops too. A foul infestation can encompass 10 to twenty of those teams of cupped leaves. You can find a slender greenish caterpillar with a blackish head as much as a ½-inch lengthy should you pull the leaves aside.

Hydrangea leaftier emerges within the spring as a small brown-and-white patterned moth that you simply in all probability won’t discover within the backyard. Its eggs are laid on the department ideas of various hydrangea species however are generally seen on Annabelle hydrangeas.

The hatching caterpillars net the leaves collectively and feed on the enclosed flower bud and surrounding leaves, which you’re observing in your backyard now. The larvae drop to the bottom later in summer season to pupate and emerge as grownup moths the next spring.

The injury is mostly minor, however a lot of cupped leaves is apparent and could be an aesthetic subject for some gardeners. An enormous infestation may cut back flowering.

Usually, this isn’t a pest that must be managed. You possibly can rigorously open the leaf pouches while you see them and smash the caterpillar inside or take away and destroy the infested leaf lots.

They’re tough to manage by spraying, since they’re protected by the leaves. You need to use a single utility of Bacillus thuringiensis kurstaki (DiPel is one commerce identify product) or a labeled pyrethroid, offering you possibly can power the spray into the cupped leaves; in any other case, the sprays won’t be efficient.

For extra plant recommendation, contact the Plant Data Service on the Chicago Botanic Backyard at [email protected]. Tim Johnson is senior director of horticulture on the Chicago Botanic Backyard.