A new study published recently by Oregon State University has flagged a new honeybee concern for two widely used insecticides. Researchers have found that the lives of bees can be shortened, with evidence of physiological stress, when they’re exposed to the products.
The researchers are not calling for a ban on the products, but rather suggesting that more information be put on product labels, and that more studies are needed to understand the sublethal effects of chronic exposure to the products.
The two identified insecticides are sulfoxaflor, the active ingredient in Transform; and flupyradifurone, the active ingredient in Sivanto. According to the researchers, this is the first study to investigate “sublethal effects” of the two products. Sublethal effects mean that the bees don’t die immediately but experience physiological stress that results in a shortened life span.
The researchers found that in the case of sulfoxaflor, the bees’ lives were severely shortened. A majority of honeybees exposed to the product died within six hours of exposure, confirming severe toxicity to bees when exposed directly to field application rates recommended on the label, the researchers say.
The western honeybee is a key pollinator of fruit, nut, vegetable and seed crops that depend on pollinators for high quality and yield. Coupled with other stressors such as varroa mites, viruses and poor nutrition, effects from these pesticides can render honeybees incapable of performing their tasks smoothly. Beekeepers and some environmental groups have raised concerns in recent years about these insecticides and their potential negative effects on bees.
A look at the study
Study lead author Priyadarshini Chakrabarti Basu, a postdoctoral research associate in the Honey Bee Lab in OSU’s College of Agricultural Sciences, is clear that researchers aren’t calling for these products to be removed. Sivanto and Transform are used to kill aphids, leafhoppers and whiteflies, among other pests. Many of these same crops that attract these insects also attract bees for pollination. There are some restrictions on their use. Transform, for example, can’t be applied to crops in bloom.
Bees might be exposed indirectly through pesticide drift, according to study co-author Ramesh Sagili, associate professor of apiculture and honeybee Extension specialist at OSU. Sagili notes the average life span of a worker honeybee is five to six weeks in spring and summer, “so if you are reducing its lifespan by five or 10 days, that’s a huge problem. Reduced longevity resulting from oxidative stress could negatively affect colony population and ultimately compromise colony fitness,” he says.
Priyadarshini Chakrabarti Basu, Oregon State UniversityBEE WORK: One cage from each of the three experimental groups in an Oregon State University honeybee study is shown here. The control cage (far left) has more live bees than the cages in which the bees were exposed to Sivanto (middle) and Transform (far right).
For the study, the researchers conducted two contact exposure experiments: a six-hour study and a 10-day study in May 2019. The honeybees were obtained from six healthy colonies at the OSU apiaries. In each experiment, groups of 150 bees were placed in three cages. One group was exposed to Transform and a second to Sivanto. The third was a control group that wasn’t exposed to either pesticide.
Honeybee mortality, sugar syrup and water consumption, and physiological responses were assessed in bees exposed to Sivanto and Transform, and compared to bees in a control group. Mortality in each cage was recorded every hour for the six-hour experiment and daily for the 10-day experiment.
While Sivanto was not directly lethal to honeybees following contact exposure, the 10-day survival results revealed that field-application rates of Sivanto reduced adult survival and caused increased oxidative stress and apoptosis in the honeybee tissues. This suggests that even though Sivanto is apparently less toxic than Transform, it might also reduce honeybee longevity and impart physiological stress, according to the study authors.
Co-authors on 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, an assistant professor and pollinator health Extension specialist.