get some Neem Oil (totally organic, made from the Neem tree)...mix it as according to directions...with a little dish soap...spray on your plants and the mildew will be gone...mine were infected really bad...took 3-4 applications of Neem (either morn or evening)...it stinks though so you can't put it on the buds....so get rid of the mildew before that...if it's just here and there, take the leaves off.....good luck....Iris

ps mildew is usually caused by a lack of circulation of air...are you outdoors or indoors? I read a post that said for an indoor grow to burn sulphur pellets....but don't know if that works....