Hydrangea leaf curl

(Question)

Our whole community has gorgeous hydrangeas…last year we removed leaves that had fused together with a green caterpillar residing within. The plants did not bloom. We have the same problem this year. Should we just pull them out? ( I hate to do this) is there domething we can do to prevent prevent this from happening? The plants are 3 years old.
Thank you !
We live in the Stouffville area.

(Answer)

Thank you for your inquiry to the Toronto Master Gardeners.   I have taken my answer to your question directly from our website.

https://www.torontomastergardeners.ca/index.php/askagardener/hydrangea-leaf-curl-with-worm-inside/

Your plants have been infested with one of two kinds of insects that create similar damage.

1. The hydrangea leaftier larva (caterpillar) binds two or as many as four leaves together with strands of silk into a cup form and then feeds and rests between them. Pulling the leaves apart will reveal a slender greenish caterpillar up to one-half inch long with a blackish head. After it stops feeding, the caterpillar will drop to the ground to pupate over the summer and emerge as an adult moth the next spring.

2.  A different insect that causes similar damage is the leafroller.  In this case, the caterpillar rolls or folds only one leaf, binds it with strands of silk, then feeds and rests within the rolled or folded leaf.

In both cases, the damage is unsightly but will not destroy the shrub. Because it occurs early in the spring, if you remove the infested leaves and smash the caterpillars, the plant will have time to grow and flourish over the summer.  Make sure to clean up the ground below the shrubs very well.

References:  University of Illinios https://hyg.ipm.illinois.edu/article.php?id=359

and US Dept of Agriculture via link from https://slugginalong.blogspot.ca/2012/10/leaf-rollers.html

So….don’t kill the plant; just break the life cycle of the invader!