generally you don't want to spray anything on flowers. even water.
if you have a serious bug problem though i'd rather spray essential oils in my garden than chemical insecticides whether veg or flower or any time.
anything you spray now will be in there when you smoke it, if thats what you're asking. i've sprayed neem oil in week 4 and not noticed any residue/odor in week 8. havent used other oils but i doubt any are more offensive than neem.