Backyard Wildlife: Bee expert talks about pesticide

In my May column, I wrote about the Bayer Crop Science Bee Center in Research Triangle Park and its studies examining the impact of neoniconitoids on bees.

Neoniconitoid is a type of pesticide made partially with nicotine that has been widely used in agricultural since about the 1980s. Various forms of the chemical were developed in response to concerns that older types of pesticides were killing numerous beneficial animals, from small mammals to butterflies and bees.

Bees, of course, are responsible for pollinating many of the crops grown in the U.S. and have been showing signs of decline for several years. The decline has been attributed to variety of factors, from loss of bee habitat because of land development to pesticide use by growers.

I heard from a few readers who objected to my conclusion that “the jury is still out” on the safety of neoniconitoids, including Clayton beekeeper Charles Heatherly, who wrote: “The worst offense of this article is to allow the Bayer spokesman to get away with the assertion that ‘...bee scientists have not been able to link pesticide, when used exactly as intended, to major drops in bee populations.’”

Feeling a bit sheepish about the absence of an opposing opinion in the May column, I decided to follow up with a scientist who studies bees and bee colony health for a living.

David Tarpy, a professor at N.C. State University and the apiculturist for North Carolina’s agricultural extension program, was the source suggested by Heatherly. Tarpy holds a doctorate in entomology from the University of California-Davis, and his research focuses on insect societies, primarily honey bee queen behavior.

I spoke with Tarpy, who agreed that the data is bit confusing.

While neoniconitoids are less damaging to wildlife than previous forms of pesticides, he said, there is still much that is unknown about results of their long-term application. Unlike traditional pesticides, neoniconitoids are most often applied by coating the crop seeds – not by spraying plants.

“There have been studies and data from both sides showing that in field-relevant doses, neoniconitoids don’t really have a significant impact on honey bee populations,” Tarpy said. “The problem is, things go wrong and there are always things you didn’t know about, indirect effects. Emerging evidence suggests that even when bees are subjected to sub-lethal doses, they may become more susceptible to diseases. These lingering things are harder to quantify, harder to see cause and effect.”

In other words, when used as instructed, the products have not been linked directly to deaths of honeybees; however, there are indirect effects that are still being studied.

Two years ago European countries placed a ban on neoniconitoids, yet bees in Europe are still having problems, Tarpy said.

“I think when applied property, growers are better off using these types of pesticides than the ones in the past known to kill bees and give us cancer,” he said.

While extremes in the pesticide/honeybee debate range from neoniconitoids as “the sole cause” for honeybee decline to the contention that they have no role at all, Tarpy concludes: “The truth is probably somewhere in between.”

This story was originally published June 26, 2015 at 6:53 AM with the headline "Backyard Wildlife: Bee expert talks about pesticide."