Annabel Hydrangea bug attack #244313 - Ask Extension

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Annabel Hydrangea bug attack #244313

Asked May 14, 2015, 1:25 PM EDT

I have found many pairs of opposing leaves sealed together at their edges to form a cocoon-like structure. Inside are tiny black eggs and a 1/4"-3.8" caterpillar or worm. I've cut off as many of these as I can find, but what is it and how to best control and then prevent?

Oakland County Michigan

Expert Response

It sounds like small caterpillars or larvae that are called leaf tiers because they tie the leaves together.  The black stuff you think are eggs is actually frass or insect excrement.   Simply, they eat and they poop. The caterpillars are neither boys or girls; they are its.  They have to become mature before they could lay eggs.

Because they have successfully folded over the leaves, there is nothing that is going to get to them if you spray. They are hiding in their little self-created tents. 

You could pull the leaves apart and squish the critters or use a product like insecticidal soap (bought, not made) and spray it directly on them.  One way or another, you want to get the stuck-together leaves apart.  If you manage to kill most of these little losers, they do not grow up to lay eggs and have their kiddies visit you next spring.

Time is short to get your leaf tiers before they do more damage and grow up.  If you are using insecticidal soap, spray the plants when the sun is off of them in the evening.  This product is very successful against soft-bodied insects.

Prevention would have been finding the caterpillars before they tied up the leaves and killing them.
Gretchen Voyle Replied May 14, 2015, 3:30 PM EDT

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