Insects "nibbling" on leaves are not likley to have prevented your shrub from blooming - something else is to blame for that. In fact, most insect damage to foliage is cosmetic only. It does no damage to the plant at all.

You can't spray to prevent insect damage. Few insecticides work that way. But you can spray or treat to control damage when/if you detect insect problems next season and have correctly identified what insect is causing the problem.

its best to mention where you are ... big city ...

it should be losing its leaves soon ... not really the time of season to be spraying anything ...

a pic might get you an idea of the culprit for next year.. but odds are.. last years bugs are rarely next years bugs ...

this is one of the hardiest plants there is around... in my experience ... cant believe it would need any interdiction ...

ken

If it didn't bloom, perhaps nearby trees have grown and are shading it out. How many hours of direct sun does it receive?

Did the buds not form? Or if they did form, did they drop? Or if they didn't drop, did they turn brown and not bloom?

could be number of reasons.