Label rates scaled to however many hives you're walking out to.
Read this first. Oxalic acid is a registered pesticide and the
label is the law. This tool does the arithmetic off the current Api-Bioxal label rates — it does
not replace the label on the package in your hand, and rates differ between products (Api-Bioxal,
EZ-OX and VarroxSan are not interchangeable). Vaporizing demands a proper acid-gas respirator, not
a dust mask: the fumes will scar your lungs and your corneas. Goggles and acid-resistant gloves for
every method. Never vaporize into a hive you haven't sealed, and stay upwind.
A seam is a gap between two frames with bees visibly in it.
Count them with the lid off before you start.
Mixing the dribble solution
Api-Bioxal
—
Sugar
—
Water
—
Makes
—
Label rate is 35 g of Api-Bioxal per 1 litre of 1:1 sugar syrup (sugar
by weight, water by volume). Mix the syrup first and let it cool, then stir the acid in. Use it
the day you mix it — dissolved oxalic acid breaks down into HMF over time, and old solution has
killed bees.
The label rates
Method
Rate
Notes
Dribble
35 g per 1 L of 1:1 syrup; 5 mL per occupied seam, 50 mL per colony maximum
Works best on a cool morning while they're in a loose cluster. Warm bees scatter and you dose them unevenly.
Vaporization
4 g per brood chamber
Seal the entrance and any cracks, vaporize, leave sealed about 10 minutes, then open up.
Extended release
4 VarroxSan strips in the lower brood chamber; on a double deep, up to 2 more in the top box only if it's fully populated with bees (6 max, not 8) — left 42–56 days
The one oxalic method that keeps working as mites emerge from capped brood.
Timing beats dosing. Oxalic acid cannot reach a mite under a capping — dribble and vapor
only kill what's riding on adult bees. With brood in the hive that's maybe a third of your mites,
which is why a single fall dribble on a brood-full colony disappoints so many people. In our part
of Pennsylvania the broodless window usually falls somewhere from late November into December.
Hit that window and one treatment can take out the great majority of the mite population.
Otherwise use extended-release strips, or a product that penetrates cappings.
There's a second broodless window most people miss, and it's in summer. Any colony you make
queenless runs itself out of capped brood — a walk-away split, or a hive that has swarmed. Once
the last old brood has emerged and before the new queen's eggs are capped, there is nowhere for a
mite to hide. That gap is usually about a week, it lands in the middle of summer when mites are
building, and it costs you nothing to use. The
split & queen timeline works out the exact dates for your hive.
Honey supers. Oxalic acid is exempt from residue tolerance requirements, and the Api-Bioxal
label permits use with supers in place — one of the few treatments that does. Confirm it on your
own label before you rely on that, and understand it's still not a great idea during a flow:
the treatment works poorly with a full brood nest anyway.