Treating with oxalic acid – how can our in-hive sensor help?

The varroa mite is a major honeybee pest and is known to be a leading cause of colony collapse. Beekeepers have several treatments available to help tackle the mite and keep its numbers low within the hive. However, varroa have evolved resistance to many treatments such as amitraz, fluvalinate, and coumaphos (Sammataro et al. 2005) prompting researchers to explore alternatives such as oxalic acid.

At the University of Nebraska, Ellis and Aliano (2005) found that oxalic acid is about 70 times as toxic to mites as it is to adult bees, but is it safe for larvae? Studies have shown that oxalic acid is very toxic to honeybee larvae and beekeepers need to be aware that using oxalic acid for varroa control, while larvae are present, could have a negative effect on the colony population size and wintering capability (Terpin, B., Perkins, D., Richter, S. et al. 2019).

Oxalic acid is recommended to be used in the winter months when the hive is mostly brood-less as treatments only kill phoretic mites and are ineffective against mites in sealed cells. So, how can you be sure your hive is brood-less without opening it up and peeking inside?

Our in-hive sensor continuously monitors temperature within the hive, specifically the brood temperature. A healthy colony with a laying queen will regulate the temperature within the brood nest to an almost perfect 34 degrees C, this an be seen on the graph below.

However, as soon as the queen stops laying and the hive becomes brood-less, the bees stop regulating the brood nest temperature, as there is no need. As can be seen in this graph.

You can be fairly confident that with a temperature that fluctuates and is much lower than 34 degrees that the queen is not laying and the hive is brood-less, making it safe, and efficient, to treat with oxalic acid.

References

Sammataro, D., Untalan, P., Guerrero, F., Finley, J. (2005) The resistance of varroa mites (Acari: Varroidae) to acaricides and the presence of esterase. Int. J. Acarol. 31(1), 67–74

Ellis, M. & Aliano, N. (2005). Prepublication presentation at the 2005 California State Beekeepers Convention.

Terpin, B., Perkins, D., Richter, S. et al. A scientific note on the effect of oxalic acid on honeybee larvae. Apidologie 50, 363–368 (2019).