I

ANNO 1 Numero 2
Roberta Ferrero [1], Paola Ferrazzi [1], Antonio Nanetti [2]

Control of Varroa destructor (Anderson & Trueman) through oxalic acid administered by sublimation or by trickling sugar solutions

[1] DI.VA.P.R.A. Entomologia e Zoologia applicate all’Ambiente “Carlo Vidano” Università di Torino (I)
[2] Istituto Nazionale di Apicoltura, Bologna (I)

The trickling and sublimation methods for oxalic acid (OA) administration in the autumn-winter control of Varroa destructor (Anderson & Trueman) were compared in continental areas of Italy (Piedmont and Emilia-Romagna). With regard to the first one, a 4.4% OA solution and 31% sucrose in water solution (w/v) was employed in Piedmont, whereas 4.2% OA solutions at variable sugar concentrations were used in Emilia-Romagna. The sublimation was attained through the use of a specific heating device (Varrox). In most cases both methods were highly effective, however the outdoor relative humidity seemed to have played a role in the development of acaricidal effect. Single administrations made when the relative humidity was above 85-90%, with 60, 30, and 15% sugar solutions, attained an efficacy as high as 94.3, 93.8, 92.9%, respectively, whereas Varrox yielded 95.8%. Double administrations made with 31% sucrose solutions attained an efficacy of 95.2 and 96.8%. Conversely, in low relative humidity conditions (Piedmont, 2003) either as dropped sugar solution or as sublimate, the average efficacy was around 60%. In Piedmont, two trickling administrations showed detrimental effects on colony size and on the honey yield. On the contrary, Varrox treated colonies and control colonies showed good conditions and great honey yield.

Contact: roberta.ferrero@unito.it; ananetti@inapicoltura.org