Abstract
Summary Amitraz is a varroacide used the longest (over thirty years) and most commonly by Polish beekeepers. This involves high risk of V. destructor developing amitraz resistance. Therefore it is necessary to monitor the effectiveness of treatments to ensure appropriate protection of the honeybee colonies. The objective of this study was to evaluate the efficacy of amitraz used as the contact varroacide (Biowar 500 formulation) to control V. destructor in honeybee colonies. Field studies were conducted in 2011 and 2012. In both years, the amitraz treatments started in the last weeks of August. Two strips of Biowar 500 (500 mg of amitraz per strip) were inserted into each colony and removed after 8 weeks. The control colonies were left untreated for 8 weeks. After removing the strips the control therapy was conducted in all colonies. The average efficacy of amitraz (E%) calculated for the two years combined, after 6 and 8 weeks of treatment, amounted to 90.6% and 94.6%, respectively. As a result of the natural mortality in the control colonies, the population of parasites lowered only by 16.4% and 23.9% during 6 and 8 weeks. The efficacy of the strips was lower in colonies with larger amount of brood.
Highlights
Over several decades, the infestation of the ectoparasitic mite V. destructor (Anderson and Trueman, 2000) has been the dominant problem of beekeeping worldwide
After 3 weeks of treatment, the strength of the control colonies significantly decreased with relation to both parameters
Amitraz effectiveness does not depend on the strength of bee colonies measured before, and after 3 and 6 weeks of the treatment
Summary
The infestation of the ectoparasitic mite V. destructor (Anderson and Trueman, 2000) has been the dominant problem of beekeeping worldwide. The recent research proved that V. destructor contributes the most to the honeybee losses in many countries (Brodschneider et al, 2010; Chauzat et al, 2010; Dahle, 2010; Genersch et al, 2010; GuzmánNovoa et al, 2010; Le Conte et al, 2010; Schäfer et al, 2010; Topolska et al, 2010; Pohorecka et al, 2011; van Engelsdorp et al, 2011; Martin et al, 2012; Nazzi et al, 2012) Fighting these mites is still a priority in beekeeping management (Delaplane, 2011). This, in turn, leads to the accumulation of the therapeutic agent residues in the hive environment (Lodesani et al, 1992; Bogdanov and Kilchenmann, 1995; Bogdanov et al, 1998; Wallner, 1999) and to the development of Varroa mite resistance to these compounds (Lodesani et al, 1995; Milani, 1999; Floris et al, 2001; Spreafico et al, 2001)
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