Varroa Control in the Summer

By Russell Smith.

After visiting a lot of commercial beekeepers in the winter months and speaking to a big number at the national conference in June, a number of facts became very clear.

  1. Varroa issues are getting worse each year.
  2. The synthetic strips do not appear to be working as well as they used to.
  3. Hives used for kiwifruit pollination were especially susceptible to getting high mite loadings.
  4. Mite numbers are building to greater numbers through the summer months than they used to.
  5. In some areas, beekeepers were adding synthetic strips in Feb at the time of honey harvest but they weren’t successful in knocking the mite numbers back before the colony collapsed.
  6. In areas with high bee populations in Autumn, mite numbers were increasing as a result of re-invasion from other hives, even though the beehives had the correct number of synthetic strips in place.
  7. Varroa mite re-invasion is a huge issue in Autumn and is a result of visits from robber bees and/or from social bee visits.
  8. This was highlighted at the conference by an excellent study done by Dr Dennis vanEngelsdorp and shown in this video Watch content from 27 min to 33 min. Remember the study was done in Autumn in USA.
  9. Beekeepers are having to do a lot more mite counts than they used to. They can’t assume what they did with synthetic strips last year will work this year.
  10. When the beehives are weakened by varroa mites in Autumn, their ability to fight off wasps is greatly compromised.


What is the solution?


Beekeepers have been using Oxalic Acid mixed with Glycerine all over the world for many years.

They have found it extremely beneficial to the health of the colony.

We now have a large number of clients in NZ using Oxalic Acid during the summer to keep varroa mite numbers down at low levels very successfully.

That means the hives are in good health after harvest and have a far greater chance of surviving the Autumn with whatever treatment the beekeeper chooses.


Oxalic Acid (OA) is an approved substance for varroa control in NZ under the “Own use exemption”.


There are many ways that beekeepers can use it but one very cost effective & popular way is to use the Beequip Strips and soak them in an Oxalic Acid / Glycerine solution.

Click here for a full instruction guide.

Click here to view the range of Oxalic packages available.


Many beekeepers are adding a set of strips to the brood box each time they add supers.


A few key points:-

  1. Oxalic acid is exempt from the requirement of an MRL (Maximum Residue Level) in NZ when used as an agricultural compound for the control of Varroa.
  2. There is nothing in NZ law that specifically states that OA cannot be used for varroa control while honey supers are present.
  3. OA is naturally present in all honey with a very large range of variation from one honey type to another.
  4. The best mix ratio for most applications in NZ has been observed to be 40% Oxalic Acid mixed with 60% Glycerine by weight.
  5. A hive with high mite loadings has a lot bees wounded by the varroa, and when the acid gets carried around the hive, it appears to be very painful to the wounded bees. We have noted that a proportion of these wounded bees will fly out of the hive, even if it is night, and die.
  6. If maximum bee numbers are an issue, the solution is to add the strips to the hive when mite loadings are low and to maintain mite control with regular treatments after that.
  7. If the OA strips are added when most of the bees are healthy, virtually zero adult bee mortality is observed.
  8. Use 3 to 4 strips per brood box.
  9. See pages 7 & 8 in the instruction guide about best strip location in the hives, and how long the strips are effective for.
  10. Even with a little extra labour, these strips still work out very cheap, especially if added to the brood box when doing an inspection anyway.


Varroa Control in Autumn.

Check out the new RobberGards.

They will make a huge difference to varroa and wasp issues in Autumn & Winter.