Biotechnical methods in colony management, and the use of Apiguard and Exomite Apis for the control of the varroa mite (Varroa destructor) in Irish honey bee (Apis mellifera) colonies

The benefits of incorporating biotechnical methods into honey bee (Apis mellifera L.) colony management for varroa (Varroa destructor Anderson & Trueman) control was evaluated. The effect of modifying bottom boards was determined by dividing the test colonies into three treatment groups: normal floor, mesh floor, and sticky floors. Invasion pressure was estimated by treating five colonies continuously with Bayvarol. The effect of drone brood trapping as a method of reducing mite populations was examined by dividing the colonies into two test groups: colonies with and without (control) drone brood trapping. In the former, a shallow (super) frame was placed in the brood box. At three week intervals, the sealed drone brood was removed and the total number of sealed cells and viable varroa mites were counted. Brood area and honey bee population were also measured on each sampling date. Standard management practices were used throughout the season. The percentage efficacy of Apiguard and Exomite Apis under Irish weather conditions was examined from August - September 2005. Both products were administered according to the manufacturer's instructions for a four week period. Total mite drop was counted and the percentage efficacy was estimated by treating all colonies with Bayvarol. Variation in floor type reduced mite population growth early in the foraging season, but the effect was not significant. In contrast, a significant benefit was realized by the inclusion of drone brood trapping as a colony management strategy for reducing varroa mite populations. Although colony development was not affected by drone brood trapping, the possible impact of removing large number of drones unnecessarily is discussed. Apiguard was more effective than Exomite Apis as an autumn treatment under Irish weather conditions. The recorded percentage efficacy (approximately 85%) was, however, relatively low when compared with that reported for elsewhere in Europe and would be insufficient as a sole autumn treatment for the effective control of the varroa mite. Results also indicate that brood area post-treatment reduced the percentage efficacy of both products, but colony development was not affected.