Apart from the efficiency of coumaphos against Varroa mites, its impact on the oxidative status and survival of the honey bee (Apis mellifera) was assessed. The research was conducted on hives from the same apiary, equalised regarding the number of bees, brood area and food storage. Based on Varroa infestation the hives were allotted to two groups: non-infested (N) and infested (I). Both groups were either treated (T) – NT and IT, or untreated (U) – NU and IU. The treatment of infested bees was controlled with a follow-up treatment with amitraz. The efficiency of coumaphos was 96-97%. This organophosphate had a negligible effect on bee survival, but it significantly affected their oxidative status: superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) activities, and the concentrations of malonyl dialdehyde (MDA). Coumaphos significantly (p˂0.0001) decreased SOD activity in non-infested bees, but increased it in those infested. By contrast, both CAT and GST activities, as well as MDA concentrations significantly increased (from p˂0.05 to p˂0.0001) after treatment in all groups, with the exception of IT, where it declined. Coumaphos in non-infested hives caused oxidative stress per se, not unlike varroa in infested colonies. However, in infested colonies it decreased oxidative stress, owing to its efficacy against Varroa mites and contributed to the recovery of bee colonies. In spite of its certain downsides, coumaphos remains an effective anti-varroa substance, but should be used with precaution, not to add to the effects of environmental factors which may cause red-ox misbalance.
