Effect of oxalic acid on the mite Varroa destructor and its host the honey bee Apis mellifera

Abstract

Here, we study the effect of oxalic acid on isolated varroa mites and on varroa mites parasitizing caged honey bees treated with oxalic acid per os or topically (by trickling or by sublimation). We also study the effect of oxalic acid (trickling and sublimation) on individual bees, focusing on their lifespan, midgut morphology and function, and Malpighian tubule morphology. Effect on mites: contact of isolated mites with oxalic acid coated surface (Petri dishes treated by sublimation) significantly decreased mite viability. In an experiment on varroa mites parasitizing caged bees treated with oxalic acid, the strongest acaricidal effect was observed following oral application and the lowest when oxalic acid was applied through sublimation. Effect on bees: oxalic acid applied by sublimation did not decrease bee lifespan over the 21 days of observation contrary to trickling, where a nonsignificant lifespan decrease was observed. Topical application of oxalic acid increased the rate of midgut cell apoptosis, with a stronger statistically significant effect seen in the group treated by trickling. However, neither trickling nor sublimation caused epithelial destruction in the midgut and Malpighian tubules or loss of digestive tract function.