By Tom J. Bechman

Christian Krupke first stated that insecticides exhausted from corn planters were collecting on flowers bordering agricultural fields and were present in beehives near those fields in 2012. The insecticides were compounds called neonicotinoids, used as seed treatments on corn.

Krupke, a Purdue University Extension entomologist, and colleagues recently published a paper in the Journal of Applied Ecology that contains information from more recent studies on this topic. The report covers both measurements of dust from planters and data from yield trials indicating no yield benefit to these insecticide seed treatments.

Naturally, not everyone sees the same take-home message in Krupke’s work and report. A seed industry spokesman, a scientist with a company that makes a neonicotinoid seed treatment and an independent researcher have other viewpoints.

Key findings
First, here are five findings reported by Krupke and his colleagues.

• Insecticide can settle up to 100 meters from the edge of planted fields. Krupke; Jeff Holland, also of Purdue Entomology; Elizabeth Long, Ohio State University; and Brian Eitzer with the Connecticut Agricultural Experiment Station found insecticides on flowers up to 100 meters out, which was the farthest distance examined in the study.

• A vast majority of bees are exposed to these insecticides. Mapping Indiana’s corn acreage and areas that may receive drift, the report says 42% of the state is exposed to neonics during planting. Using public data and projecting foraging patterns, the report says 94% of honeybees could fly through areas that contain lethal doses of insecticide.

• The study found no evidence that neonics increase yield. The authors tested treated and untreated corn seed at three locations in Indiana. There were differences in pest damage at one site, but that did not translate into yield loss.

• Target pests may be scarce. The report notes that this study and inconsistent findings in the U.S. and Europe “suggest that the current use levels of insecticidal seed treatments in North American row crops are likely to far exceed the demonstrable need, and our results likely reflect a scarcity of pests.”

• Risk to bees and other non-target organisms could be even bigger. The authors conclude that the risk to bees may be even more significant than their paper indicates, since the study was limited to 100 meters and only involved cornfields.

Exclusive interviews
Penton Ag discussed the report with several people in the ag industry. Here are additional comments from Krupke about his findings.

What is the bottom line for you after conducting this study? There are actually two bottom lines. First, insecticides attached to dust particles escaping from the planter could actually be going far beyond the planting area. As documented in our study, it’s actually going much farther than we expected.

What is your other take-home point? We could not find any yield benefits in our tests over three years.

How many yield trials did you do? We did three trials in both 2012 and 2013, and two trials in 2014. They were replicated, small-plot trials. They were small plots because it’s difficult to get seed corn which isn’t treated.

Kevin Cavanaugh

Kevin Cavanaugh offers his insight on the latest report and on seed treatment insecticides, in general. He is Beck’s director of research.

Will there be changes in the seed industry based on this report? No, not likely. Nearly all seed corn in the industry is treated with neonic insecticides. About 70% of soybeans are treated, although not all those are treated with insecticides. We also treat wheat seed because there’s demand for it.

What can be done to reduce risk? We’re using fluency agents, which don’t allow much dust to leave the planter. You don’t see it blowing in the wind. We’re keeping dust and any insecticides attached to it in the planter. Other farmers could do this, too.

Why do you anticipate that you will continue offering treated seed? The reality is that farmers want this product. This debate has been public for five years, and I’ve yet to have the first farmer tell me that he doesn’t want neonic seed treatment on his seed. Yes, some of the pests these products control are inconsistent. But with planting earlier and trying to be efficient, farmers don’t want to take the risk. They want the insurance provided by knowing seeds are protected.

Dave Fischer

Dave Fischer is director of pollinator safety for Bayer CropScience.

Can insecticides such as neonics be toxic to bees? Yes, absolutely. There are LD50 levels set for the active ingredients in seed treatment insecticide products.

You have looked at the recent report in the Journal of Applied Ecology. What are your comments? They measured dust at various distances from the field, and it shows that there is risk of exposure to neonics. However, there is a huge difference between risk of exposure and risk of effect.

Can you explain that further? Yes. Based on my interpretation of their data, the LD50 level, which is the level at which the active ingredient is toxic, is about 100 times higher than the levels they found outside fields. What struck me was that the concentrations of insecticides they found were very low.

Could there be an additive effect of exposure at low levels over time? That’s not likely. Neonics are rapidly metabolized within the body. These substances are nothing like PBBs or DDT, where residues can remain in body fat for long periods. The bottom line is that yes, there is risk of exposure to bees, but not a high risk of effect.

Pete Nowak

Pete Nowak is a former professor at the University of Wisconsin-Madison and an independent seed researcher with Ag Informatics.

Your business is to compile reports of research and other information, correct? Yes. We compiled results of 3,359 studies from universities and other places related to neonics. That includes 800 trials on corn. Compared to no treatment, the average yield increase over 800 trials was 17.4%.

What does your information say about farmers’ attitudes toward neonic seed treatments? We surveyed 3,000 farmers. By a very large margin, farmers believe there’s an advantage to using these products. They say it’s cheap insurance, and most aren’t willing to take the chance of planting without it.

What are your thoughts about this issue going forward? Underground pests controlled by these insecticides are highly variable. The problem is that the techniques used by Integrated Pest Management developed decades ago work best on aboveground pests. Until we have new IPM techniques that can more accurately predict presence or absence of these belowground pests, I expect farmers will continue to rely on these insecticides.