UNIVERSITY PARK, Pa. (WHTM) — For years, honey bee colonies have been dying off at alarming rates. According to one study, between April 2019 and April 2020, there was a 43% colony loss across the United States. When you consider that one-third of the food we eat comes from crops pollinated by honey bees, “alarming” really is the right word for the situation.

But what causes the dieoffs? There are a lot of possibilities, and a lot of studies about the possibilities, but many of them zero in on a single possible cause, or only study one part of the country. A new study by Penn State researchers took a different approach.

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According to Luca Insolia, first author of the study, “Some previous studies have explored several potential stressors related to colony loss in a detailed way but are limited to narrow, regional areas. The one study that we know of at the national level in the United States explored only a single potential stressor. For this study, we integrated many large datasets at different spatial and temporal resolutions and used new, sophisticated statistical methods to assess several potential stressors associated with colony collapse across the U.S.”

The research team gathered publicly available data about honey bee colonies, land use, weather, and other potential stressors from the years 2015 to 2021. “In order to analyze the data all together, we had to come up with a technique to match the resolution of the various data sources,” said Martina Calovi, corresponding author of the study. The researchers used the resolution-matched dataset they created, as well as statistical modeling techniques they developed, to study the potential stress sources at the same time.

The research team found that multiple stressors impact honey bee colony loss at the national level, including pesticides, frequent extreme weather events, and weather instability. In addition, the parasitic mite Varroa destructor, which reproduces in honey bee colonies, can weaken the bees and transmit viruses. The researchers found that losses typically occurred between January and March, likely related to challenges with overwintering- but not all states follow this pattern.

“Our results largely reinforce what regional studies have observed and confirm that regional patterns around these stressors are actually more widespread,” said Insolia, a beekeeper himself. “These results also inform actions that beekeepers could take to help circumvent these stressors and protect their colonies, including treatments for the Varroa mite‚ especially in areas of weather instability. Beekeepers could also consider strategies to move their colonies to areas with high food availability or away from nearby pesticides or to provide supplementary food during certain seasons or months with frequent extreme weather events.”

The researchers would also like to use their techniques to do a deeper dive into information at the local level.

“In many cases, beekeeping associations and other organizations collect this data, but it is not made available to researchers,” said Calovi. “We hope our study will help motivate more detailed data collection as well as efforts to share that data — including from smaller organizations such as regional beekeeper associations.”

To read the original study, click here.