By Matt Hayes
periodiCALS, Vol. 6, Issue 2, 2016
Foraging for food in the flowers of crops—and in the process pollinating crops from apples to zucchini—bees are essential to billions of dollars in annual agricultural production worldwide, and $500 million in New York alone. Our agricultural success has been due in no small measure to an alliance with our partner pollinators. But last year, more than 50 percent of the honeybees in New York perished, on the heels of a decade of decline for managed and wild bees alike.
Disease outbreaks, diet, habitat fragmentation, pesticide exposure and even sub-optimal beekeeping practices have all been raised as possible contributors, and experiments parsing their relative importance and possible interactions are providing exciting clues. CALS research scientist Scott McArt, Ph.D. ’12, started by asking just what managed honeybees are actually eating.
Honeybees typically forage about a mile away from their hive in all directions, more rarely up to nine miles. While orchards near Lake Ontario often have expansive swaths of apple trees, elsewhere in New York, orchards are often rimmed by woody areas or nearby fields planted with diverse crops, offering more complex environments for bees.
For a project funded by the New York Farm Viability Institute, McArt and his students systematically inventoried individual pollen grains carried by bees back to hives placed in 30 New York apple orchards. Those bees tasked with pollinating apple trees, it turns out, only foraged about 10 percent on apples, gathering pollen from up to 20 different sources during apple bloom.
“Honeybees are brought to orchards to pollinate apples, but the bees don’t know that,” McArt said. “Our data show that honeybees are pollinating apple, but they’re also visiting many other plants during the apple bloom period.”
McArt and colleagues also quantified pesticides in the pollen that honeybees carried back to the hive. While fungicides for apple diseases were the most abundant pesticides in honeybee-collected pollen and correlated with apple pollen foraging, the levels of insecticides—which account for the greatest pesticide risk to bees—reflected the number of non-apple pollen types collected by bees.
“The pesticide results are very interesting. Our results suggest that the greatest pesticide risk to bees during apple pollination is coming from non-focal crop sources of pollen. Whether these pesticide residues are coming from contaminated wildflowers in the field margins or other sources in the agricultural landscape is clearly a topic we need to investigate further.”
Cornell researchers are also working to figure out the relative importance of diseases versus pesticides. A $2.2 million project funded by the National Institutes of Health and led by McArt will better explore how pathogens spread among the 416 bee species in New York. And this summer, as lead of the newly established New York Tech Team for Beekeepers, Emma Mullen, honeybee extension associate, visited hobby and commercial beekeepers for detailed assessments of their practices and the environments to which bees are exposed.
By measuring aspects such as pest and virus levels and taking wax samples to determine pesticide levels, Mullen will be able to compare health and survival rates and give beekeepers specific actions they can take to improve bee health—and, by extension, the availability of our state’s most important food crops.
“By next year, we hope to have identified the vital attributes to bee colony health and steps to improve operational success for beekeepers of all sizes,” Mullen said. “Ultimately, we’ll be describing best practices for healthy, productive and viable colonies.”