. >> for several years now, tibor has watched large stocks of his beloved honeybees die off. >> bees just sitting on plant leaves, hundreds of bees running around in the grass not coming home, twitching and spas spasmin fronts of the hive, a good population of the colony has disappeared. >> reporter: the flight is part of a crisis among the colonies. according to a report by the federally federal government said the healthy loss hovers around 15%. but in the winter between 2010 and 2011 the loss of managed honeybee colonies on average was 30%, well over the acceptable range. the following year, 22%, then the death rate rocketed back up to 31% in the winter of 2012-2013. and this past season at 23%. the u.s. department of agriculture has been closely watching high losses . over researchers see a range of other lethal factors such as viruses, parasites, environmental changes and pesticides. >> we'll reach a threshold where it's not going to be worth it for a bee keep for maintain a colony only to see 40% of his colonies die every year. >> reporter: bees are highly evolved socially and