Randy Oliver, commercial beekeeper and scientist, has investigated and summarized the factors involved in colony losses this winter, including the contribution of pesticides. In this lengthy two-part analysis he has obtained many opinions from both commercial beekeepers and scientists.
By now, most everyone has heard that honey bee colonies died in massive numbers this winter. Reporter Dan Rather, in his newscast Buzzkill, showed unfortunate beekeepers, some of whom had lost half or more of their colonies, predicting gloom and doom for the bee industry. What were the causes of this year’s bee shortage? As Rather says, “Everyone has an opinion.” The question is whether those opinions are based upon fact! So let’s go over the events leading up to the bee supply debacle.
Setting the Stage
Nearly 800,000 acres of almond trees in California came into bloom this winter—the trees typically start flowering about Valentine’s Day, and the bloom lasts for only about two weeks. Almonds require cross fertilization between adjacent rows of varieties, and honey bees are trucked in from all over the country to do the job (roughly a million and a half colonies). Many large commercial beekeepers move their hives into California in November to overwinter in holding yards; others build them up on winter pollen flows in Florida or Texas, or hold them in temperature-controlled potato cellars until shortly before bloom. The hives are generally placed into the orchards about a week before the first flowers appear. There is virtually no forage in the orchards prior to, or after bloom in many areas.
The Lead Up
Two seasons ago there was also a shortage of bees in almonds, following the coldest January (2011) in 17 years (cold being a major stressor of wintering bee colonies). Beekeepers then replaced their deadouts with package bees and splits, thus starting a new generation of colonies, which tend to have lower varroa mite levels than established colonies. These colonies entered autumn 2011 in pretty good shape, and then enjoyed the fourth warmest January (2012) on record! As a result, there was the lowest rate of winter mortality in years, and plenty of bees for almonds in 2012.
I was curious as to whether the colony loss rate was linked to the use of neonicotinoid insecticides. There is no recent USDA data, so I went through the California Pesticide Use Reports (data available through 2010). I plotted the amount of imidacloprid applied to crops in California in the preceding year in red (the seed treatment clothianidin didn’t even make the top 100 list of pesticides applied). Although there appears to be a possible correlation from 2006 through 2009, the trends were reversed for 2010. I will be curious to add the 2011 data when it becomes available.
In March of 2012 I received a phone call from a California queen producer who had a prescient insight as to a potential brewing disaster. He was receiving calls for queen bees from Northern beekeepers whose bees had already grown to swarming condition due to the unseasonably warm spring weather.
The queen producer noted that such early brood rearing also meant early mite buildup, and predicted that since most Midwestern beekeepers treat for mites by the calendar, that they would unknowingly allow mites to build to excessive levels before treatment. This was strike one against the bees.
To continue reading, click here: What Happened to the Bees This Spring 2013