If they haven't sprouted you are at least in a position where you can't ruin what you got or have wasted too much time. What soil are you using cause i've heard that re-using old soil or non-sterile soil is what causes this. Being that the pyrethins evaporates away quickly would make me think that you should be ok to spray and personally i'd probably try it. Hopefully one of the pros on here can step in and correct me if im wrong.