I noticed this last year lots on our Invincibelle but now I am seeing it this spring on our Bobos :(.
(I proceeded to spritz all of our Bobos with diluted dormant oil).
Any advice?
This message was edited May 29, 2016 8:50 PM
Pest \"sews\" the leaves together minimizing blooms?
The curling of hydrangea leaves at this time in Spring could be caused by one of two insects.
The hydrangea leaftier larva 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 apart the leaves will reveal a half-inch-long slender green caterpillar with a black head.
The leafroller insect also causes similar damage, but rolls only one leaf, then feeds and rests within the rolled leaf.
Both insects cause unsightly damage, but won’t kill the shrubs (the infestation would have to be huge). When you see the damage in early spring, open the leaves to inspect the contents and squish the buds that you find. If this rates a 1,000 in your EEEEECK Scale (and it is higher in mine), you can also remove the infested leaves and squash the caterpillars. Clean up the ground below the shrubs, too, because the caterpillars drop to the ground and pupate in the summer as they emerge as adult moths.
The leaftier worm hatches from its egg and 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. Looks like a black-headed green worm. The pocket begins to become brown as the contents inside the leaf pocket has been thoroughly eaten.
Both insects tend to prefer Annabelle-like hydrangeas for some reason (H. arborescens) but the other hydrangeas are not immune to this pest. They also tend to return back if one takes no action.
You can also use BTK (Bacillus thuringiensis var. kurstaki); it is also useful to spray as a preventative, when new growth emerges in early to mid-May.
Occurrences of curling earlier in time this Spring might indicate winter damage; you usually would also see more leaves damaged with no insects inside. More damaged-looking, tiny new leaves that do not open would suggest a spider mite infestation that affects new growth but... you would see webbing preventing the new tiny leaves from opening.
This message was edited May 30, 2016 2:32 AM
Pulling apart the leaves will reveal a half-inch-long slender green caterpillar.
This is it.
Both insects cause unsightly damage, but won’t kill the shrubs
I wasn't concerned that this would happen but rather if left unchecked there would be reduced flower production.
you can also remove the infested leaves.
There are lots of flower buds that seem to be infested. I guess if one removes these affected leaves/buds one still might get flowers (as Invincibelle and Bobo flower on new wood) but it would be later in the season?
You can also use BTK (Bacillus thuringiensis var. kurstaki)
As I recall this is not considered toxic to humans...right? (And so it should be readily available for sale still).
You can cut the leaf at the petiole, which is the little string that connects the leaves to the stem. This will not hurt the flower buds being developed (or to be developed).
See below for Btk info:
https://extension.entm.purdue.edu/GM/PDF/GMquestions.pdf
Looks like a black-headed green worm.
That is exactly what I found within the "sewn leaves".
You can also use BTK (Bacillus thuringiensis var. kurstaki)
I applied this last night. Thanks for the help 'Luis'.