Assegid Garedew

Microcalorimetric and respirometric investigation of the effect of temperature on the antivarroa action of the natural bee product-propolis

The antivarroa action of propolis and its synergism with temperature was investigated calorimetrically and respirometerically, using female Varroa destructormites from adult workers, worker- and drone broods. The treatment of Varroa mites with 4% propolis affected their metabolic activity, with the influence directly related to the temperature of treatment. The changes in heat production and oxygen consumption rates, as a function of temperature, showed similar patterns before as well as after treatment with 4% propolis. The mites collected from worker- and drone broods reacted similarly to propolis treatment at different temperatures. In contrast, the mites from adult workers, phoretic mites, responded differently: the treatment with 4% propolis at 40 ◦ C resulted in 100% mortality of mites from adult workers but only reduced the heat production rate of mites from worker- and drone broods by 68 and 60%, respectively. Exposure of mites to 45 ◦ C agitates them as witnessed by the elevated heat production rates (23.5 ± 2.5W/mg compared to that at 35 ◦ C with 14.4 ± 1.0W/mg). After treatment with propolis at 45 ◦ C all mites died regardless of their origin indicating that the simultaneous use of varroacides and high temperature treatment for a short period of time could be more effective rather than the prolonged use of either method.

Microcalorimetric investigation of the action of propolis on Varroa destructor mites

Abstract Treatment of Varroa destructor (Anderson and Trueman) mites with propolis has displayed both narcotic and lethal effects. The length of narcosis and rate of mortality showed dependence on the concentration of propolis used, the duration of contact time and the extraction procedure. Investigation of the action of propolis on the heat production rate of Varroa mites was performed by means of a Biocalorimeter (BCP 600). Calorimetric results point to the fact that even weak propolis concentrations with feeble lethal effects have a strong influence on the specific heat production rate. Thus, treatment with a 20% propolis solution in 40% ethanol resulted in a mortality rate of only 34% but dropped the heat production rate by 75%, a corresponding 5% propolis solution had no lethal effect but reduced the specific heat production rate still by 37% and treatment with a 0.5% propolis solution in 55% ethanol resulted in a non-significant mortality rate of 7% but reduced the specific heat production rate by 29%. Propolis showed a strong impact on the structure of the calorimetric power–time (p–t) curves. The usually highly structured p–t curves were smoothed due to treatment even with weak propolis concentrations.