Each year, I've noticed greater populations of the Hydrangea Leaftier (Olethreutes ferriferana). Today, I counted nearly all of the tips of the Annabelle Hydrangeas in our planting bed having these worms cocooning themselves between the terminal sets of leaves.
|When you find these pockets made from leaves mixed in with the lovely snow-ball flowers, you can help but be curious.|
They won't kill off the plant. It just stunts the plant from flowering. What is a Hydrangea without its Mop-head blooms?
Soon after the Leaftier worm hatches from its egg, it travels to the terminal shoots of the hydrangea. It excretes a silken thread that binds the two unfurling leaves together. Making a dandy shelter for it to feast and pupate.
|When you open these "pockets", inside you'll see a black headed green worm and its castings (frass pellets). It eats the flower and any newer leaves developing inside until it pupates. Quite ingenious method of survival.|
Generally, one wouldn't even notice these leafy pockets, until the contents inside have been thoroughly eaten. The pocket begins to become brown and at this point, the worm has begun its pupating journey to become an adult moth.
No topical pesticide is useful, since they make these elaborate shelters. The way to get rid of them is to pinch off these pockets and or open them up and squish the worm inside. Many times, the worm has just sealed off the leaves and has not eaten the flower within. BTK (Bacillus thuringiensis var. kurstaki) is also useful to spray as a preventative, when new growth emerges in mid-may.
I've sprayed newly emerging foliage with water to dislodge any young worms from getting to the terminal shoots in early-May, to mid-June. Although, it's quite an arduous task and it may damage new leaves. Just keep your eye on the tips of the new growth. Generally when Bridal Wreath Spirea (Spiraea x vanhouttei) is in full bloom, is when young worms begin to bind the terminal leaves together.
Here is a picture of an adult moth:
|Photo: Mississippi State University_ Moth Photographers Group|
Ridding the plant of as many cocooned nests as you can, will eventually rid you of the moth ever returning to lay more eggs. You may lose some flowers this year, but next there will be less moths.