![]() ![]() Widespread resistance to commonly used acaricides poses a serious threat to efficient chemical control of the parasite and makes the development of novel methods urgent, particularly those targeting mites in the brood, thus not contributing to increase the parasite's virulence. The mite can parasitize both adult bees and pupae, but it is during the pupal stage, when reproduction takes place, that it causes most damage, such that eclosing bees often bear very high viral loads associated with crippled wings and drastically reduced lifespan. ![]() In particular, Varroa plays a central role in the transmission and activation of deformed wing virus (DWV), resulting in devastating overt infections. The parasite causes a number of detrimental effects on bees at the individual level and is involved in the transmission of bee viruses. Since the recent shifting from the original host Apis cerana to Apis mellifera, the parasitic mite Varroa destructor has become the most serious threat to honeybees worldwide and plays a fundamental role in the decline of honeybee colonies observed in the Northern Hemisphere in the last decade. For these reasons propolis is regarded as an important component of social medication in honeybees. Furthermore, by reducing the hive's microbial load, propolis allow bees to invest less in individual immune function and may prime the detoxification pathways, with consequent beneficial effects at colony level. Due to its antimicrobial properties, propolis can have a direct effect on several hive pathogens, including Paenibacillus larvae, Ascosphaera apis and Nosema ceranae, that are the causal agents of American foulbrood, chalkbrood and nosemiasis, respectively. Propolis is also used to seal unwanted open spaces within the hive, to wrap the dead body of possible intruders and for polishing the honeycomb cells between successive brood cycles, although information about this latter use is scarce. Propolis is a substance deriving from resins collected by foragers on plants, and used by honeybees to coat the walls of the cavity hosting their nest. ![]()
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