Corn Planting Sends Tremors Through Bee Country

Posted by .

Sometimes laboratory science and the reality of what’s happening on the ground intersect in a graphic way. That’s what struck me this morning as I was watching a video shot by Minnesota beekeeper Steve Ellis on May 7.

Ellis has documented the die-off of bees on the very day that neighboring fields were planted with corn. As the camera pans the landscape and shows bees dead or so disoriented that they can’t even forage, Ellis talks about the fact that corn seeds coated with a type of pesticide called neonicotinoid is to blame. Such claims are not new, but a recent Purdue University study has made it clear we can no longer ignore the relationship between our pollinator crisis and pesticide use in farm country.

As we’ve written about in the Minnesota Conservation Volunteer, pollinators are the kinds of keystone critters we all can play a role in helping—or hurting. As I realized while producing two LSP Ear to the Ground podcasts (episodes 54 and 60) on the subject, everyone from beekeepers to entomologists agree on that one.

We need to keep that in mind even when doing things that are seemingly unrelated to the lives of bugs. For example, when buying a potted plant or figuring out how to control the growing emerald ash borer menace, we may want to think twice about the unintended consequences when it comes to the health of our apian workhorses.

Every third bite of food is directly or indirectly connected to the work of pollinators. And wild habitats such a native prairies wouldn’t be quite the same if bees and other bugs weren’t hauling pollen from plant-to-plant.

That’s why scientists are frantically trying to figure out why honeybees seem to be suffering so much from Colony Collapse Disorder and other maladies these days. And why are their wild cousins in decline as well (including here in Minnesota)? Is it habitat loss, feedlot beekeeping, introduced diseases or the stress of becoming the insect version of migrant workers by being transported across the country to custom-pollinate almond groves? Or is it, as University of Minnesota bee expert Marla Spivak believes, a complicated combination of factors?

One part of the mix that cannot be ignored is pesticides, which have dogged wild and domestic pollinators since they became ubiquitous after World War II. Bees and other pollinators are notoriously sensitive to pesticide poisoning. And because bees are natural born collectors, they often bring chemical contaminants back to their hives.

A Penn State study released in 2008 showed that low levels of over 70 pesticides and metabolites of those pesticides were present in hives. Most of them were common insecticides and herbicides, including atrazine, used in agriculture and around the home. Penn State researchers are particularly concerned that when the pesticides combine in a hive, they can have a synergistic effect hundreds of times more toxic than any of the pesticides individually.

Up until quite recently it was thought labeling restrictions (no spraying during the middle of the day when bees are most likely to be foraging) and a transition to chemicals of lower toxicity made it less likely bees would be killed outright by spraying. Iowa’s agriculture department has a “Bee Rule” that limits applications of insecticides labeled as dangerous to bees.

However, research has shown that a new class of pesticides could offer a more insidious threat to bees and other pollinators. In recent years, organophosphate insecticides, which are toxic to mammals and birds, have been replaced by a class of pesticides called neonicotinoids. Derived from nicotine (yes, the same stuff that makes your body crave Marlboros and Copenhagen), these bug killers are systemic, meaning they are put on a plant’s seed, or injected straight into the roots or stem. They work their way up to the leaves, killing insect pests that feed on the plant.

The advantages to these kinds of bug killers are many: for one thing farmers, greenhouse keepers and homeowners aren’t spraying toxins in the open air, reducing the chance of the chemical going where it’s not supposed to. In addition, it works specifically on insects, offering little threat to other creatures, including humans. That’s the main reason neonicotinoids have become one of the most widely used pesticides—particularly in greenhouses, by landscape companies and in homes. If you bought a potted plant recently, likely it’s been fortified with neonicotinoids. And over 90 percent of all corn seed planted in this country this spring is coated with the neonicotinoid insecticides.

“I can’t impress on you how common this is on everything,” U of M entomologist Vera Krischik told me, adding that these types of pesticides can stay in a plant for up to a year.

A few years ago Krischik noticed that after feeding on some potted plants that were in her backyard, bumblebees would become disoriented, and fall to the ground where they would suffer from tremors before dying: a classic sign of neonicotinoid poisoning (the Steve Ellis video shows honey bees suffering from tremors).

She did follow-up research and found that plants containing the neonicotinoid insecticide imidacloprid caused high death rates in beneficial insects like pink lady beetles, green lacewings and parasitic wasps.

The effects of neonicotinoid insecticides such as imidacloprid on local non-target species such as bees is of particular interest now that the emerald ash borer, a devastating killer of ash trees, has arrived in the Minnesota and other Midwestern states. This class of pesticides is one borer-control tool being promoted by tree experts.

“This pesticide isn’t all bad. It’s just not a good idea if it finds its way into plants insects use for nectar,” says Krischik.

It also turns out this class of pesticides may not “stay” within plant tissue as much as we’d like. What the Purdue University study found was that during the spring bees near corn fields are exposed to “extremely high concentrations of neonicotinoids in waste talc.” In other words, all that dust formed when a planter passes over a field isn’t just dirt—it also contains neonicotinoids, and bees may be getting doused in it. That may explain why Steve Ellis’ bees were suffering the same day neighboring fields were being planted with corn.

Fifteen European Union countries recently voted to ban neonicotinoid chemicals after they were linked with bee die-offs there. Bayer CropScience, the major manufacturer of neonicotinoids for corn, denies there is any evidence that its pesticide is linked to bee die-offs. But the scientific (and video) evidence is getting increasingly hard to ignore.

Spivak says it’s unlikely pesticides are the only cause of CCD or other mass bee die-offs. Typically in a CCD situation, one colony will collapse and a neighboring one won’t, although the bees often forage in the same areas where pesticides were applied.

“But the pesticides are a problem,” the entomologist told me. “And we need to pay attention to them, whether they are the root of the problem or not.”

One Response to “Corn Planting Sends Tremors Through Bee Country”

  1. John Martin

    I have a garden and orchard that rely on bees for pollination. Apples were serviced well by a few honey bees, and wood bees as well. Just noticed, as have some of my neighbors, that there are suddenly no bees of any kind in the garden . Beans, peppers, etc are not setting fruit like they should.

    Bees forage on corn pollen for food. The corn is tasseling and has been for about a week. Coincidence?

    I walked through the neighbors corn. Didn’t find any dead bees, but I did find a few ants, and several dead and dying deer mice. The soil looks like a garage floor.