CORVALLIS, Ore. — The lives of honey bees are shortened — with evidence of physiological stress — when they are exposed to recommended application rates of two widely used commercial pesticides, according to new research from Oregon State University.
This is the first study to examine sublethal effects of sulfoxaflor (the active ingredient in Transform) and flupyradifurone (the active ingredient in Sivanto).
In a study published in the journal PLOS ONE, researchers in Oregon State’s College of Agricultural Sciences found detrimental effects in bees exposed to Transform and Sivanto — two pesticides developed to be more compatible with bee health and approved for use in the United States.
The western honey bee is a major pollinator of fruit, nut, vegetable and seed crops. These crops rely on bees for pollination to ensure high quality and yield. Exposure to pesticides — when combined with other stressors such as varroa mites, viruses and poor nutrition — can hinder honey bees’ ability to function properly.
Beekeepers and environmental groups have raised concerns about the negative effects of these insecticides in recent years.
According to the researchers, this is the first study to examine sublethal effects of sulfoxaflor (the active ingredient in Transform) and flupyradifurone (the active ingredient in Sivanto). Sublethal effects do not immediately kill bees but result in physiological stress and reduced lifespan.
In the case of Transform, most of the bees died within six hours of direct exposure to recommended application rates, confirming its severe toxicity, the researchers said.
Call for better labeling, not bans
Lead author Priyadarshini Chakrabarti Basu, postdoctoral research associate in the Honey Bee Lab in the College of Agricultural Sciences, said the research team is not recommending that Transform or Sivanto be taken off the market.
“We are suggesting that more information be put on the labels of these products, and that more studies need to be conducted to understand sublethal effects of chronic exposure,” Basu said.
Transform and Sivanto are used to control aphids, leafhoppers, whiteflies and other pests. Many crops that attract bees for pollination are also treated with these pesticides. Some restrictions do exist — for example, Transform may not be applied to blooming crops.
Bees may be exposed indirectly
Bees can be exposed indirectly through pesticide drift, said study co-author Ramesh Sagili, associate professor of apiculture and Extension honey bee specialist in the College of Agricultural Sciences.
“The average lifespan of a worker honey bee is five to six weeks in spring and summer, so if you are reducing its lifespan by five to 10 days, that’s a huge problem,” Sagili said. “Reduced longevity resulting from oxidative stress could negatively affect colony population and ultimately compromise colony fitness.”
How the study was conducted
The researchers conducted two contact exposure experiments — a six-hour study and a 10-day study — in May 2019 using bees from six healthy colonies at the Oregon State apiaries. In each experiment, groups of 150 bees were divided into three cages. One group was exposed to Transform, a second to Sivanto, and a third served as a control group.
Researchers assessed honey bee mortality, sugar syrup and water consumption, and physiological responses. Mortality in each cage was recorded hourly during the six-hour experiment and daily during the 10-day experiment.
Sivanto also showed sublethal impacts
While Sivanto was not directly lethal following contact exposure, results from the 10-day experiment showed that field-application rates reduced survival and increased oxidative stress and apoptosis (programmed cell death) in honey bee tissues. The authors concluded that, although less toxic than Transform, Sivanto may still reduce honey bee longevity and cause physiological stress.
In addition to Basu and Sagili, co-authors of the study included graduate student Emily Carlson and faculty research assistant Hannah Lucas, who both conduct research in the Honey Bee Lab; and Andony Melathopoulos, assistant professor and Extension pollinator health specialist.
