Oxalic acid for mite control is used early spring or late fall when little or no brood is present to treat varroa mites. Api-Bioxal can be applied either via the dribble or vaporization/sublimation method. You can also spray package bees following the instructions on the Api-Bioxal label. This 35g package can treat 20 colonies using the dribble method and 35 colonies using the vaporization/sublimation method. Warning: Use protective mask, gloves, and glasses, and long sleeves when mixing and applying oxalic acid. Api-Bioxal has a 5-year shelf life.