Oxalic acid is a naturally occurring acid within the hive. We can use this acid from common wood bleach, sold at most hardware stores, to create a last varroa mite treatment for the fall before we seal the hives for winter. Keeping our bees varroa free greatly increases their chances of winter survival. When the bees are clustered in their hive in late fall, find a day where the temperatures reach 50ºF or greater. Here in Central New Jersey, we perform our Oxalic Acid Dribble treatment around Thanksgiving.
600mL warm water
35g wood bleach
600g white table sugar (roughly 3 cups)
Mix the warm water and wood bleach until the bleach crystals are dissolved. Next add the table sugar and stir until the sugar is dissolved. Test the temperature to ensure it will not scald the bees.
To apply to the bees, dribble with a syringe at the rate of 5mL per seam. A seam is the gap or space between the frames within the hive. Do not exceed more than 50mL per colony. Again, ensure the temperature outdoors is around 50ºF.