It is late April in Maine (5b-4a), and the columbine and iris are just
peeking out. Every year I have problems with budworm in the iris and
columbine worm in the columbine. I'd like to try to get them early
with Neem and/or insecticidal soap. Can either of these harm very
small plants (probably not the iris, but maybe the columbine?)

Any other suggestions for coping with these would be appreciated.