i once had an infestation so bad that towards the end of the plants lives i would use a vacuum. using the wand or tube attatchment i would carefully vacuum the bugs off where i could see them. don't spray anything on buds that are four weeks or less from harvest (thats just my personal rule). the biggest problem at this late stage in the game is how many bugs you smoke in each bowlful. i hate smoking spider mites and assume you probably will too. get as many off as you can before smoking. or screw it and torch those little f-ers. as they say smoke-em if you got-em.