News from Cornell University:
new Cornell study of New York state apple orchards finds that
pesticides harm wild bees, and fungicides labeled “safe for bees” also
indirectly may threaten native pollinators.
The research, published June 3 in
Proceedings of the Royal Society B, finds the negative effects of
pesticides on wild bees lessens in proportion to the amount of natural
areas near orchards.
Thirty-five percent of global food production benefits from insect
pollinators, and U.S. farmers have relied exclusively on European
honeybees, whose populations have been in decline for decades due to
colony collapse disorder.
“Because production of our most nutritious foods, including many
fruits, vegetables and even oils, rely on animal pollination, there is
an intimate tie between pollinator and human well-being,” said Mia Park,
an assistant professor at the University of North Dakota and the
paper’s first author, who worked on the study as a Cornell entomology
graduate student. Co-authors include professor Bryan Danforth and
associate professor John Losey, both in entomology.
“With honeybee numbers in decline, relying on wild pollinators and
encouraging the services they provide seem very important,” Park said.
The researchers studied 19 New York state apple orchards over two
years, 2011 and 2012. They determined the health of bee populations by
analyzing the numbers of wild bees and honeybees and the number of
species for each orchard. They also created an index of pesticide use
from low to high use, then quantified the amount of natural areas that
surrounded each orchard.
“We found there is a negative response of the whole bee community to
increasing pesticide use,” Park said, adding that fungicides also are
contributing to the problem.
The effects of pesticides on wild bees were strongest in the
generation that followed pesticide exposure, Park said, possibly
suggesting pesticides affect reproduction or offspring. Park said her
research only looked at one generation to the next, and more study is
The study found no effect of pesticides on honeybees, but
European honeybee hives are brought in to an orchard for short periods
during blossoming then removed. In addition, growers are careful not to
spray while honeybees are in the area. “Honeybees may have shown a
response if they were allowed to stay,” Park said.
“Our studies of wild bees in apple orchards are showing how important
wild bees are for apple pollination in the eastern U.S.,” said
Danforth. With more than 20,000 known bee species, native bees are
abundant and diverse in many agricultural habitats, and likely pollinate
watermelons, squashes, blueberries and other orchard crops, he said.