CORVALLIS, Ore. — By the time she was studying the mechanics of stag beetle pinchers as an undergraduate student, Emily Carlson knew she had been bit by the research bug.
Literally.
“Basically, I just got them really angry, saw how hard they could pinch, and then dissected their heads,” Carlson said.
Disclaimer: Beetles aren’t “true” bugs, but in the United States they are referred to colloquially as bugs.
Carlson went on to work in natural resources nonprofits and local governance as she figured out what bug to devote her time to. This experience set her up well to pursue a doctorate at Oregon State University, where she conducted research in the Honey Bee Lab and Pollinator Health Program.
Carlson, who graduated in June, is the lead author on a study in the highly respected journal PLOS ONE that showed that the existing tool used to monitor honeybee pesticide exposure fails to capture important data. The finding is an important reference for policymakers and researchers.
Her co-authors on the study were Ramesh Sagili, professor of apiculture and Oregon State University Extension Service honeybee specialist in OSU’s College of Agricultural Sciences, and Andony Melathopoulos, Extension pollinator health specialist and associate professor in the College of Agricultural Sciences.
Bees and pesticide
In 2013, a pesticide application in Wilsonville led to the largest documented mass fatality of bumblebees in North America. The estimated deaths doubled to 100,000 based on new research in 2021.
The Oregon Legislature responded by funding both OSU’s Pollinator Health Program and the position that was filled by Melathopoulos in 2016. Carlson’s research builds upon the program’s foundation by filling in a key gap.
“You can report on bee poisonings, but there is no system to try to understand what pesticides are out there and what bees are exposed to them,” said Carlson. Both the Environmental Protection Agency and the Office of the Inspector General in the U.S. Department and Health and Human Services have identified this as a big problem.
It’s no easy feat. “Bees are a very interesting agricultural product, because unlike cows, you can't put a fence around them. You can't tie little leashes to them. They're going to forage where they want to forage,” Carlson said.
So instead of monitoring the bees, researchers monitor the pollen bees collect, which can be distinguished by species and identified by unique protein structures.
Hazard quotient
Currently, pesticides are broadly monitored with a unitless metric called a hazard quotient that determines how much pesticide hazard bees experience.
Understanding hazard quotient involves exposure, hazard and risk. Carlson compares it to coffee consumption.
“We know that caffeine in a high enough dose can cause death, so caffeine itself is a hazard,” Carlson said. “It has the potential to cause harm.”
“But you have to think about your exposure,” she said. If someone has a cup of coffee a day, their exposure to the hazardous substance is low, therefore they are at a low risk of harm.
Hazard quotient attempts to communicate that same risk but for bees and pesticides. Instead of coffee, the vehicle is pollen. The quotient is widely used in literature and monitoring, researchers debate if it can accurately convey risk.
Additionally, there isn’t clear guidance on how much pollen must be tested and from how many sites to accurately monitor risk. That is where Carlson’s research comes in.
The experiment
Carlson set out to calculate how many sample sites — that is sites where the pollen was collected — were needed to detect a 5% annual change in hazard quotient every year for a five-year period. To get data, Carlson collected pollen from hundreds of hives across various crops.
Carlson discovered that the detecting shifts in risk varied widely by crop. One crop only needed 139 sites and cost less than $150,000 to detect the shifts in risk; another needed over 7,000 sites and cost over $3 million.
Carlson’s research challenged hazard quotient as an imprecise and expensive tool.
“I am not trying to communicate with this study that we need to entirely throw hazard quotient out of the window,” Carlson cautioned, noting its usefulness in assessing general hazard.
“This study highlights testing the assumptions we have about our systems,” she said. “We have had hazard quotient for at least 10 years, and this is the first study that ever asked the question: How many sites do we need to monitor to get a good understanding of how hazard changes?”
Information is lost in hazard quotient, as well, she said. For example, bees pollinating carrots are exposed to pesticides. The pollen is tested for pesticides. Is it the pesticide used on the carrots, or did it come from another source?
A useful metric would be determining the specific pesticide present in the pollen. If it’s from an outside source, growers can invest in projects like drift barriers — plantings designed to deflect pesticide spray. If it is from the pesticide on the carrots, then the grower could make choices about the frequency of application to protect bee colonies.
Bees and growers
The emphasis on protecting bees from pesticides may suggest there is some animosity between growers and beekeepers. That is the furthest thing from the truth, Carlson said.
Commercial beekeepers and growers are partners. “Commercial beekeepers don’t make their money through honey sales,” said Carlson. “They make their money through pollination contracts with almond growers, cherry growers, blueberry growers, etc., because those farmers will get much better fruit if there are bees in the field.”
Both growers and beekeepers have a strong interest in limiting bees’ exposure to pesticide. That’s why they partnered with Carlson on the research.
“We are so lucky to have beekeepers who will put their livelihood in our hands and let us use their beehives for research,” said Carlson.
“The bees are being paid to pollinate,” said Carlson, who laughed and then corrected herself. “Well, the beekeeper is paid on behalf of the bees, but the bees are getting benefits.”
Carlson’s research was supported by the Oregon State Beekeeping Association, the Natural Resource Conservation Service in the U.S. Department of Agriculture, the Foundation for Food and Agriculture Research, and the National Science Foundation’s Graduate Science Research Fellowship.
