Modern beekeepers seldom keep honeybees exclusively for beeswax production. Queen breeders are specialist beekeepers who raise queen bees for other beekeepers. She is a beekeeper and a member of the British Beekeepers Association. Bee brood is harvested by beekeepers in many countries. In 2006, U.S. commercial migratory beekeepers reported sharp declines in their honey bee colonies. Some beekeepers provide a pollination service to other farmers. These benefitted the crop-growers, vineyard growers (winemakers), and the beekeepers and shepherds, respectively. Contract pollination has overtaken the role of honey production for beekeepers in many countries. The mite "Varroa destructor" has become the largest single problem faced by beekeepers worldwide. Some villagers were fishermen, beekeepers, or trappers. The popularity of this hive is growing among 'sustainable-practice' beekeepers. Hollow sections of black gum trunks were formerly used as bee gums by beekeepers. As part of this event she established the European forum of beekeepers and farmers. Medieval beekeepers used castoreum to increase honey production. These beekeepers might not produce any honey for sale.