Issue |
Apidologie
Volume 32, Number 1, January-February 2001
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Page(s) | 49 - 55 | |
DOI | https://doi.org/10.1051/apido:2001110 |
Apidologie 32 (2001) 49-55
First detection of strains of Varroa destructor resistant to coumaphos. Results of laboratory tests and field trials
Massimo Spreafico, Francesca Romana Eördegh, Iris Bernardinelli and Mario ColomboIstituto di Entomologia agraria, Milano University, Via Celoria 2, 20133 Milano, Italy
(Received 5 May 2000; revised 19 September 2000; accepted 28 September 2000)
Abstract
The susceptibility of four populations of Varroa destructor to the organophosphorous
acaricide coumaphos was studied. The mites were taken from apiaries kept in Lombardy
(northern Italy) and tested with a laboratory assay on paraffin wax with known
concentrations of coumaphos. The susceptibility of two populations to coumaphos
was close to that of susceptible populations, indicated in the literature
(LC50 at 24 hours: 12.6 g/g); a third population showed a significant, but slight
increase in tolerance (LC50 at 24 hours: 29 g/g) while the fourth population had a
much higher LC50 (>200 g/g at 24 hours). In subsequent field trials carried out in
the apiary in which the latter population had been sampled, the total average
efficacy of two treatments with Perizin® (the commercial formulation of coumaphos)
in colonies without capped brood was 46% (28-88% ).
Key words: coumaphos / Varroa destructor / resistance / bioassay / field trial
Correspondence and reprints: Massimo Spreafico
e-mail: colomar@mailserver.unimi.it and mario.colombo@unimi.it
© INRA, EDP Sciences, DIB, AGIB 2001