(Beyond Pesticides, April 25, 2017) Past use of agricultural pesticides puts honey bees at risk across multiple growing seasons, according to research from scientists at Cornell University in New York. According to lead author Scott McArt, PhD, “Our data suggest pesticides are migrating through space and time.” Honey bees, which over the past decade have experienced unsustainable declines over 40% each year, are at great risk from exposure to a range of pesticides, chiefly the neonicotinoid class of insecticides. This new research adds to calls from beekeepers, environmental groups, and progressive farmers to transition agriculture away from pesticide-dependent practices.
Cornell researchers conducted a massive study that analyzed both the pollen source and pesticide residue found therein for 120 experimental hives placed near 30 apple orchards in New York State. The landscapes surrounding each orchard were classified based on the amount of natural area or agricultural land that was present. Scientists analyzed risk to honey bees by collecting information about pesticide use during the growing season as well as the amount of pesticide contamination in “beebread,” pollen tightly packed unto pellets by bees used as food or in the production of royal jelly.
“Beekeepers are very concerned about pesticides, but there’s very little field data,” said Dr. McArt in a press release. “We’re trying to fill that gap in knowledge, so there’s less mystery and more fact regarding this controversial topic.”
Results showed that while nearly every colony collected apple pollen, it comprised a relatively small percentage of total forage – roughly 9% of total pollen on average out of the 120 hives. The most frequently sought pollen was buckthorn, which was also found in nearly every hive, but averaged 39% of the total quantity collected.
While the amount of land used for apple production correlated with higher numbers of pesticides found in beebread, that data point alone does not indicate a higher risk to pollinators. In this case, the type of pesticide detected made a difference. Consistent with current agricultural practices, significant quantities of fungicides are used on apple crops. However, researchers determined that insecticides put honey bees in greatest danger. In fact, most of the insecticide load in colonies was determined to be from pesticide applications made in prior years. In 28 out of 30 orchard sites, pesticides not sprayed during that year are detected, totaling 64% of total pesticides found, with roughly 2.8 novel pesticides discovered at each site. The researchers indicate that this is consistent with trends found in other studies, which have shown wildflowers and field margins to contain high levels of pesticides years after these chemicals were applied.
Overall, 17% of colonies have pesticide levels so high they present an acute hazard to honey bees, while 73% contain residues that indicate a chronic exposure risk. Ultimately, researchers determined that neonicotinoids as well as a range of other insecticides present significant risks to pollinating honey bees.
“We found risk was attributed to many different types of pesticides. Neonicotinoids were not the whole story, but they were part of the story.” Dr. McArt said in a press release. “Because neonicotinoids are persistent in the environment and accumulate in pollen and nectar, they are of concern. But one of our major findings is that many other pesticides contribute to risk.”
Results of this study are consistent with past research from Cornell University. A study published in 2015 focused on wild pollinators and found that as the number of pesticide applications increased, wild pollinator numbers subsequently decreases. While this current study calculated risk based on lab-derived toxicity data, the prior study found empirical evidence of lower numbers of wild pollinators when fungicide applications are made before bloom, and insecticide applications are made after bloom occurs. It follows that while fungicides may present a lower toxicological risk on paper, their influence in real-world conditions, where these fungicides are likely to be combined with other pesticides, indicates their effects may be more significant than previously assumed.
Concerned individuals can join in the protection of pollinators by encouraging their local and state officials to enact strong policies that protect these critical species. With one in three bites of food dependent on crop pollination, including nutrient dense foods like apples and almonds, urgent action is needed now. Learn more about how you can get involved by visiting Beyond Pesticides’ BEE Protective webpage.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.