well there re a lot of options for you before you go to all out chemical warefare,but to answere your question if yousing either avid or floramite you should wait until the cuttings have roots,at least 2 weeks old.you can spray them but you dont want to get any over misting in the water.the best way 2 do it is to take your cuttings,plant them in your media then after the roots show get a plastic container and fill it with water,dump your chemicals into the water.then dip your plants into it,really coating them.put a lid on the chemical and water mixture and save it.repeat this process in 2 weeks. thats it.u should never have to use those chemicals again....word of warning when yousing avid or flora mite i reallly suggest that you use a resperator that has cartriges made for hazardous conditions.the cartriges should have these abbreveations on them CL/HC/SD/CD/HF/OV. and be niosh approved.i would also suggest clothes you can throw away and some rubber gloves.