Queen Caging and Oxalic Acid Treatment: Combined Effect on Vitellogenin Content and Enzyme Activities in the First Post-Treatment Workers and Drones, Apis mellifera L

Varroa destructor is a mite causing colony collapse in Apis mellifera. Common solutions for beekeepers to control Varroa mites are drone brood removal and queen caging and/or chemical treatments with formic or oxalic acid. Treatments performed against Varroa mites may affect honey bee welfare; they have the potential to cause negative effects on the immune system, as well as oxidative stress. In this study, effects of the combination of queen caging and oxalic acid treatment on both the immune system and antioxidant enzymes of first post-treatment generation workers and drones are investigated. The combination of the above anti-varroa treatments did not produce significant effects on the antioxidant system of the first post treatment generation. However, within the immune system, such treatments determined a decrease in glucose oxidase activity in drones, and an age dependent variation in vitellogenin content in worker bees. Such effects may result in cuticular sclerotization issue, dehydration, and pathogens transmission in drones, and in a general weakness of the immune system of both drones and workers with a subsequent higher risk of illnesses. Further investigations to assess the physiologic effects of such enzymatic activity variation on the welfare of honey bees subject to queen caging and oxalic acid treatment are desirable.