Evaluating and optimising formic acid treatment against varroa mites on honey bees with MOx-sensors and a control loop

In many parts of the world beekeepers report high numbers of honey bee colony losses, which is both an environmental and an economical problem. Varroa mites (Varroa destructor) are a major factor of honey bee colony losses. Many beekeepers use formic acid to fight varroa, but treatments show low efficacy when weather conditions are suboptimal or the acid is not handled correctly. To monitor different treatment approaches, a sensor setup with commercially available MOx gas sensors has been implemented and used for comparative measurements. With the sensors installed in the bee hive, the acid level can be measured continuously - which also allows to set up a control system. Together with adequate hardware for automated acid application and a closed loop approach, the varroa treatment can be made more stable. It also allows for optimization of its efficacy, since target values for acid concentration and duration of the treatment can be adjusted and tested in a reproducible way. We provide a thorough discussion of advantages and disadvantages of the MOx technology.