UMD Researchers, Partners Find Unusually High Summer, Low Winter Hits to Survival
Preliminary results of the 14th annual nationwide survey conducted by the nonprofit Bee Informed Partnership showed that beekeepers across the U.S. lost 43.7% of their managed honey bee colonies from April 2019 to April 2020, with record summer losses.
Beekeepers across the United States lost 43.7% of their managed honey bee colonies from April 2019 to April 2020, with record summer losses, according to preliminary results of the 14th annual nationwide survey conducted by the nonprofit Bee Informed Partnership (BIP).
The losses are the second largest since the partnership began conducting the survey in 2006 with data collected and analyzed by the University of Maryland and Auburn University, measuring well beyond the average annual loss rate of 39%.
The survey results highlight the cyclical nature of honey bee colony turnover: Although the high loss rate was driven by a rough summer for colonies, winter losses were markedly lower than in most years, at 22.2%, 6.4 points lower than the survey average. Summer losses were reported at 32%, 10.4 points above the average.
“This year, summer loss was actually the highest we’ve ever recorded, even higher than winter losses, which is only the second time we’ve seen that, and it’s mostly commercial beekeepers that are driving that loss number, which is unusual,” said Nathalie Steinhauer, BIP’s science coordinator and a postdoctoral researcher in the University of Maryland Department of Entomology.
Since beekeepers began noticing dramatic declines in their colonies in the early 2000s, state and federal agricultural agencies, university researchers and the beekeeping industry have been working together to understand the cause and develop best management practices. The BIP annual survey has been an integral part of that effort.
“When BIP started doing this survey, winter loss was the main focus because that period of the year was thought to be the most challenging for beekeepers and their colonies, especially in temperate climates,” said Geoffrey Williams, assistant professor of entomology at Auburn and co-author of the survey. “Adding summer loss into the survey in 2010-11 was quite revealing. For the first time, we had the numbers to show that loss occurs throughout the year, and that summers are not insignificant for beekeeper losses.”
The survey asks beekeeping operations of all sizes to track the survival or turnover rates of their honey bee colonies. This year, 3,377 beekeepers managing 276,832 colonies across the country responded, representing about 10.4% of the nation’s estimated 2.67 million managed colonies.
According to Dan Aurell, BIP field specialist based at Texas A&M University, the health of the queens that head production colonies is a major factor in summer losses. In addition, beekeepers split their colonies after winter to strengthen them as a best management practice, and the health of those colonies at that time is critical to their longevity.
On the other hand, he said, winter loss is closely related to fall management practices, such as whether colonies have good conditions during the summer to build a robust fall population, and if the population of the parasitic varroa mite was up.
“I’ve heard beekeepers say that the California queen raising season in 2019 was the worst in 30 years,” Aurell said.
Commercial beekeepers typically have lower losses than backyard and smaller operations, but that hasn’t been the case in the past year, when commercial colonies were hit hardest. Because commercial honey bees pollinate $15 billion worth of food crops in the United States each year, their health is critical to food production and supply.
And commercial losses are costly, Aurell said, with 400 colonies costing upwards of $80,000 to replace.
Many of the summer losses this year could represent carry-over from a particularly poor winter last year, when BIP reported the highest winter losses ever, 37.7%. Higher levels of the varroa mite may have weakened colonies going into spring 2019. Additionally, weather conditions may have promoted brood diseases, affected the availability of mated queens when they were needed, or contributed to a lack of food for honey bees.
“There is always going to be some turnover,” Steinhauer said, “but it is about what is a normal turnover and what is abnormally high, and how BIP can help arm beekeepers with the information they need to manage it.”
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