You mentioned an insectiside. Have you tried fine
misting the leaves, both top and under, with Seven ?

Slugs and snails may be the culprits.

Don't know much about those critters.
They do make a non-toxic bait for them.
One source:

http://www.pestproducts.com/sluggo.htm

Mother Nature has no cost answer ;-)

{{gwi:365980}}