Abstract
Gamma irradiation is known to inactivate various pathogens that negatively affect honey bee health. Bee pathogens, such as Deformed wing virus (DWV) and Nosema spp., have a deleterious impact on foraging activities and bee survival, and have been detected in combs. In this study, we assessed the effects of gamma irradiation on the flight activities, pathogen load, and survival of two honey bee stocks that were reared in irradiated and non-irradiated combs. Overall, bee genotype influenced the average number of daily flights, the total number of foraging flights, and total flight duration, in which the Russian honey bees outperformed the Italian honey bees. Exposing combs to gamma irradiation only affected the age at first flight, with worker bees that were reared in non-irradiated combs foraging prematurely compared to those reared in irradiated combs. Precocious foraging may be associated with the higher levels of DWV in bees reared in non-irradiated combs and also with the lower amount of pollen stores in colonies that used non-irradiated combs. These data suggest that gamma irradiation of combs can help minimize the negative impact of DWV in honey bees. Since colonies with irradiated combs stored more pollen than those with non-irradiated combs, crop pollination efficiency may be further improved when mite-resistant stocks are used, since they performed more flights and had longer flight durations.
Highlights
The performance and productivity of honey bee colonies greatly depends upon their health.Worldwide, the continued decline in honey bee health impedes the profitability of beekeeping operations
When daily foraging flights were analyzed by cohorts, the average number of daily flights was consistently higher in the Russian honey bees than the Italian honey bees, but significantly differed only in Cohorts A (F = 5.13, p = 0.025; Italian = 3.23 ± 0.14 flights per day, Russian = 3.85 ± 0.17 flights per day) and C (F = 6.30, p = 0.014; Italian = 3.14 ± 0.19 flights per day, Russian = 3.9 ± 0.24 flights per day)
When all of the data were pooled, the flight duration was longer in Russian honey bees honey bees (1070.25 ± 63.44 min) than the Italian honey bees (876.50 ± 54.84 min) (F = 6.41, p = 0.012)
Summary
The performance and productivity of honey bee colonies greatly depends upon their health. Deformed wing virus (DWV), which is characterized by causing wing deformities in honey bees, is transmitted vertically from queen to worker, horizontally from worker to worker or worker to larvae, and by varroa mite-feeding [5]. In addition to varroa mite-feeding as a route of pathogen infection for honey bees, diseases can be acquired from used combs since the wax harbors many contaminants, including various pathogens. Gamma irradiation technology has been used to reduce exposure to and control pest problems in a variety of settings It is currently used in food decontamination to kill food-borne pathogens and pests to increase the shelf life of various fruits and vegetables [20,21]. We used flight activity as a proxy for colony performance and fitness [39]
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