whats up farmer... hows it goin?
i personally wouldnt spray plants in flowering after about week 5 UNLESS you have a very strong ventilation and air circulation system...
this is because water will undoubtedly make is way into the buds when you spray... if you dont have good circulation and ventilation the humidity from spraying will be contained within the grow room.. the extra moisture in the air will cause liquids to evaporate slower... this may/can lead to problems like mold/mildew or bud rot... non of which are good...
i personally think at week 5 the buds are still "small" enough to evaporate out the liquids without much problem in most cases... i still recommend having a good vent system (at all times.. not just for spraying) anyways...
now.. if you are having pests problems after week 5 to harvest here are some things you can do..
1) neem oil can be root fed... it will work the same way it does as a spray.. just from the inside out.. and pests do not like the taste of it all.. so it will deter them even further from eating your plants... just add 1 to 2 tbls with each watering until the very final flush.. doing this will not change how your buds taste in the end... so dont worry there...
2) there are some foggers that can be used up until harvest.. normally i would stay away from chemicals and chemical foggers/sprays... but sometimes it is needed... if you do need to fog make sure that the fogger you use is useable on vegetables or other edible crops and that it can be used up until harvest....
you should try to have the pest problem taken care of or at least thoroughly in check before harvest if you can... i wouldnt spray or mist the plants with anything to "wash off" whatever you use.. it wont be needed if you use the right stuff...
http://homeharvest.com/insectspraystotalreleasefoggers.htm this can be used safely up to 2 days prior to harvest.. make sure you get the correct size can for the area you are fogging.. dont over do it...
if i can help out anymore feel free to ask...