Varroa treatment-free colony losses in the European honey bee ( Apis mellifera): a review of published literature

Varroa treatment-free beekeeping has been practised for decades throughout Africa and Latin America and is becoming more popular in Europe and the USA. This type of management relies on the bees developing Varroa resistance, replacing the use of varroacides and biotechnical control methods. Many national and statutory bodies, for instance in the UK, Spain, France and Germany, advise or even legislate against Varroa treatment-free beekeeping. This review brings together published data on honey bee colony loss within the first 5 years of the transition of colonies to Varroa treatment-free management. It also looks at long-term data on treatment-free colony survival. In the transition phase, four types of strategy were identified of which two were particularly successful: 1. starting with known Varroa-resistant bees; or 2. starting with non-resistant bees and then selecting bees showing resistant traits, whilst mitigating losses with biotechnical methods in the first summer, followed by requeening in colonies with high Varroa counts. In both strategies, winter colony loss was 6–17% and was similar to control colonies (8–23%). Colony losses were higher (27–28%) if treatment was stopped in colonies without any mitigating strategies other than standard colony management, such as swarm capture or colony splits. If colonies were left untreated without any management, other than winter feeding, the majority died after 3 years, although up to 11% of colonies survived 5 years. Once Varroa treatment-free apiaries were established, they have been shown to survive for 20 years or more. The advice given against treatment-free beekeeping therefore is misplaced.