The pesticides, called neonicotinoids, became popular among farmers during the 1990s. They're used to coat the seeds of many agricultural crops, including the biggest crop of all: corn. Neonics, as they're called, protect those crops from insect pests.
But they may also be killing bees.
Christian Krupke, a professor of entomology at Purdue University in Indiana, is among the scientists whose research has alarmed beekeepers. Last month, I caught up with Krupke at a DoubleTree Hotel in Bloomington, Ill., where he was giving a talk to several hundred farmers and the agricultural consultants who advise them about seeds, fertilizer and pesticides. The meeting was organized by GrowMark, a farm supply company.
This was a skeptical audience, filled with people who make their livings using or selling pesticides. They listened quietly as Krupke laid out the reasons why neonicotinoids have fallen under suspicion.
These pesticides are typically applied to seeds — mainly of corn, but also other crops — as a sticky coating before planting. When a seed sprouts and grows, the chemicals spread through the whole plant. So insects, such as aphids, that try to eat the plant also get a dose of poison.
But could they be killing more than aphids? Krupke put up a picture of a beehive surrounded by a carpet of dead honeybees. In several places across the Midwest, there have been reports of bees dying in large numbers like this. And tests detected the presence of neonics on them.