Acute contact toxicity test of oxalic acid on honeybees of the southwestern zone of Uruguay.

Leonidas Carrasco-Letelier1*, Yamandú Mendoza1, and Gustavo Ramallo1

This work studies the acute contact toxicity of oxalic acid (OA) on a honeybee polyhybrid subspecies (Apis mellifera), which is the dominant biotype in southwestern Uruguay (SWU) and the country’s most important honey-producing region. We determined the mean lethal dose (LD50), as well as the no observed effect level (NOEL) and the lowest observed effect level (LOEL) values. We also estimated the total number of honeybees per hive in the test area. The aim was to assess the relationship between the maximum OA dose used in Uruguay (3.1 g OA per hive) and the toxicological parameters of honeybees from SWU. The current dose of 3.1 g OA per hive corresponds to 132.8 g OA per honeybee since determined NOEL is 400 mg OA per honeybee; our results indicate that the current dose could be increased to 9.3 g OA per hive. The results also highlight some differences between the LD50 value in SWU honeybees (548.95 mg OA per honeybee) and some published LD50 values for other honeybee subspecies.

Keywords: LD50, Varroa destructor, Uruguay.
1Instituto Nacional de Investigación Agropecuaria (INIA), Estación Experimental Alberto Boerger INIA La Estanzuela, Ruta 50, km 11, Colonia, Uruguay. *Corresponding author (lcarrasco@inia.org.uy).