Pollinators, pesticides in focus at Fruit Research and Extension Center

BIGLERVILLE, Pa. -- An apple orchard in full bloom: for many, a simple harbinger of spring. But for David Biddinger and his colleagues and graduate students at Penn State’s Fruit Research and Extension Center, the delicate blooms carry the promise of a future in which bees and pesticides can do their work in harmony at fruit farms across the nation. Their work is part of ongoing efforts across the College of Agricultural Sciences and throughout the University to develop a holistic approach to pollinator health, an area in which Penn State has built a strong reputation.

Even in low doses, some pesticides have been found to have negative effects on bees and their offspring, said Biddinger, who is an associate professor in Penn State’s Department of Entomology. At the core of the research whether subtle alterations in the timing of early-spring pesticide applications or choice of pesticide can reduce or even eliminate bees’ exposure.

It's all about timing

For three years, Biddinger and his team have been studying this by applying about a dozen commonly used pesticides to specific apple trees in a patch of rolling Biglerville orchard, varying timing each year. Researchers don’t worry about the amount of compound on the leaves of the trees because bees’ contact is limited to the insides of flowers, which have not bloomed at the time of application. Rather, researchers measure trace amounts of the compounds that end up in pollen and nectar, which are meticulously collected from each tree during the spring bloom.

Back in the lab or in field trials, bees are exposed to corresponding levels of compounds and the health of the colonies is measured over multiple generations.

“What we’re trying to do is learn from field experience, using the same spraying methods and timings as a grower, to see what a bee is actually exposed to [as a result of their foraging for pollen and nectar],” said Biddinger. “We know some of these compounds have what we call sub-lethal effects. They wouldn’t kill a bee in 48 hours, but may kill a bee down the road.”

Biddinger said some compounds may appear to have no effect on a current generation of bees, but lead to sterility or other problems in the following generation. “So this work will help us to determine realistic field exposure levels. If an entire generation of bees is exposed, even at low levels, we want to know what’s going on.”

The controlled environment of the lab will help researchers to determine best practices for the application of pesticides, which should lead to healthier bees and crops.

Early results

Early results have been intriguing. Sarah Shugrue, a master’s student in entomology whose work has focused on this question, was in the orchard as this year’s round of apple blossoms popped, pollen-collection tools in hand.

“Last year, we sprayed five days earlier than we normally would have. We found that the pesticides were still effective against the pests we were trying to prevent, but levels in pollen and nectar were significantly reduced,” Shugrue said.

“We have found that we control the pests just as well and the residue levels drop below the point of detection if we apply earlier,” Biddinger said. “So, we can use a product that may be toxic to a bee, but won’t impact that bee if we adjust the timing of the application.”

Shugrue, who recently graduated, said she chose Penn State’s entomology program because she wanted to make an impact.

“Penn State has one of the nation’s top entomology programs,” she said. “I knew I wanted to go into some sort of application of entomology, not just research, so I thought going to a school that has a track record for making an impact, and faculty members who have the same record, would be a good idea.”

Biddinger said results have been published in various academic journals and Penn State Extension publications for fruit growers, such as the Penn State Fruit Times and the Tree Fruit Production Guide. Additional publications can be found at the following links: 1, 2, 3, 4, 5.

Biddinger will join researchers and agricultural industry leaders the International Conference on Pollinator Biology, Health and Policy, being held on Penn State’s University Park campus from July 18-20.