In January, the Environmental Protection Agency released its preliminary risk assessment of imidacloprid’s impact on pollinators. This risk assessment helps fulfill EPA’s commitment to the president’s pollinator strategy. The preliminary risk assessment, which focused only on honeybee impact, will be followed by a full ecological and human health assessment to be released in December 2016.

Jill Calabro, science and research programs director for AmericanHort, is a bit concerned about how the industry will compile enough solid scientific data in time to meet EPA’s deadline. We asked her to catch us up on a controversial issue: pollinators and neonicotinoids.

Matt McClellan: Where does the industry currently stand with imidacloprid and other neonicotinoid pesticides?

Jill Calabro: There haven’t been any major regulatory changes lately, which is a very good thing. But there is still a tremendous amount of pressure from certain non-governmental organizations pressuring different stores to discontinue the sale of plants that have been treated with neonicotinoids. That pressure does not seem to be letting up.

MM: Home Depot and Lowe’s have made plans to phase out neonic-grown plants by 2018 and 2019. Are other retailers making similar moves?

JC: That’s what I have heard. I also have heard that Ace and TrueValue Hardware are being targeted, along with various other stores that sell plants. I think that will continue.


MM: So are we looking at the end of neonics?

JC: I really hope not. Our thought process at AmericanHort and the Horticultural Research Institute is that we are hoping that good decisions are made based on sound science. Hopefully this EPA risk assessment will be truly based on sound science.

MM: What were the EPA assessment’s conclusions, and how could they affect horticultural policy?

JC: The preliminary assessment was more encouraging than we had expected it to be, but it doesn’t include ornamentals. They haven’t evaluated ornamentals yet. So it is very unclear at this stage what the impact for ornamentals will be. The EPA is looking for data on ornamentals, but it is just not available yet. There are several studies underway to get the type of information they’re requesting, however given the vast amounts of variability in ornamental plant material, this is a huge undertaking. It’s very unclear what EPA will do with regard to ornamentals. They haven’t stated their plan of attack. So we are very concerned.

MM: A recent Washington State University (WSU) study measured honey bee colony exposure to four neonicotinoid insecticides (clothianidin, dinotefuran, imidacloprid, and thiamethoxam) in urban, rural and agricultural settings. What did the researchers find?

JC: The WSU study classified each hive as being in either urban, rural or agricultural landscape. They found greater numbers of (neonic) residue in beebread from hives in agricultural landscapes. That is not too surprising, but what was surprising was that of all the residues detected were all well below the EPA’s own designated 25-part-per-billion label.

In rural or urban landscapes, they found less than 5 percent of beehives in a two-year period had any detectable residues at all. The authors of the study concluded there is no risk of adverse effect on beehives in rural and urban landscapes, and there was a very low risk in agricultural landscapes. The highest amount found was 3.9 parts per billion in an agricultural landscape. EPA considers 25 parts per billion the cutoff for potential for adverse effects.

MM: How does the methodology of that WSU study differ from other studies that have been done?

JC: Even in the EPA’s own studies, the first level they evaluate is individual honeybee sensitivity to neonics. Those honeybees are fed from neonic-treated sources for a period of six weeks. It’s a very conservative approach, which I can certainly appreciate, but it is not realistic in terms of what happens in the real world. It’s not representative.

What was neat about the WSU study was that they looked at the whole colony level, not individual bees. They looked at entire beehives and apiaries. They studied 149 beehives in various regions of the state. That was significant, too. It was a statewide evaluation, and not a lab study, or one particular area. These were actively managed beehives, and the bees were allowed to feed and forage as they normally do. The researchers just collected wax and beebread samples periodically, and tested the wax and beebread for residue of neonicotinoids.

MM: Will this study affect policy or methodology of other studies?

“It’s very unclear what EPA will do with regard to ornamentals. They haven’t stated their plan of attack. So we are very concerned.” — Jill Calabro, AmericanHort science and research programs director

JC: I certainly hope so. I hope EPA looks at the results of the study. I don’t expect EPA to change their methodology, but I hope they consider the data and the conclusions that were drawn by the researchers.

MM: You mentioned that EPA needs more data before the final report, which will include ornamentals. Is this the type of research they want?

JC: They just want more data. A lot of the data is generated directly from the registrants as part of the registration process, which is normal. But this issue of residue analysis hasn’t been asked for in the past, especially with ornamentals. It’s very expensive and it’s very difficult to get products registered on ornamentals, period. There is little incentive for them economically speaking, to register products for ornamentals. That’s why the IR-4 group was established, to help our industry have more tools available to us. IR-4 is playing a key role in attaining this data for EPA.

MM: What role is IR-4 playing in the neonic matter?

JC: They are helping to facilitate a large grant proposal to get more residue information. It also looks at bee attractiveness of plants. We’re calling it a “mega-proposal.” It’s a $7 million grant request for the USDA SCRI grant program. I’m hopeful that it will be approved this year. We have been asked to submit the full proposal, which is very encouraging. It includes all sorts of different levels, but this information will be very important for the analysis.

MM: What about existing research into the effects of neonics on pollinators?

JC: HRI funded five different grants in 2015 that were pollinator focused. (Learn more at Some residue data will be collected from that, but it is extremely difficult to collect enough pollen for residue analysis and nectar. One researcher estimated you need 200 to 300 flower heads to get enough for one sample of nectar. It’s arduous. The amount of man hours that is involved is also great. It’s a very expensive, time-consuming undertaking.

A lot of samples have been collected, but they still need to be analyzed. We are waiting for those reports, which should come in the next few months. That should help with EPA’s final risk assessment, but I am really nervous about what they’ll do with ornamentals.

The preliminary assessment released earlier this year only included agricultural crops. It focused on honeybees and agricultural crops. It did not look at other pollinators like bumblebees or native bees, or ornamental crops. They admitted they don’t have full data on all the ag crops yet, but only two crops were flagged as a potential risk: cotton and citrus with foliar sprays. Even that can be mitigated, so it does not mean neonic use will go away permanently. I hope it does not. It would be terrible to lose this class of chemistry as an option.

Matt is managing editor for Nursery Management magazine, a GIE Media Horticulture Group publication.