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American Bee Journal

Notes from the Lab – September 2020

By September 16, 2020 No Comments

Neonicotinoid insecticides: When there’s risk to bees, when there are economic benefits to users, and when there are viable replacements

Neonicotinoid insecticides. If you’re like many people who we interact with, you just read those two words and already have an opinion. Perhaps such a strong opinion that there’s little point to us writing more.

But for those brave souls who are willing to wade into the science on neonicotinoids (neonics, for short), here’s your chance. We just published a 432-page report in which we comprehensively synthesized all literature on risk to pollinators (>400 peer-reviewed studies regarding exposure to and effects from neonics) and economic benefits to farmers/applicators (>5,000 paired neonic/control field trials) for each context in which neonics are used. In addition, we summarized all application contexts in which neonicotinoid insecticides could be reliably replaced by alternative chemical insecticides or non-chemical pest control technologies or techniques.eonicotinoid insecticides. If you’re like many people who we interact with, you just read those two words and already have an opinion. Perhaps such a strong opinion that there’s little point to us writing more.

So, for our thirty-third Notes from the Lab, we’re going to summarize the main take-home messages from “Neonicotinoid insecticides in New York: Economic benefits and risk to pollinators,” written by us and freely available for download at:
https://pollinator.cals.cornell.edu/pollinator-research-cornell/neonicotinoid-report/.

Why did we write this report? Two reasons. First, like many of you, we’ve been surprised by the lack of a comprehensive synthesis on this topic that’s relevant to policy makers. A synthesis that quantifies risk to pollinators and benefits to farmers/applicators for each context in which neonics are used. There is potentially risk to pollinators from every chemical insecticide, and there are potentially economic benefits to users for every chemical insecticide. But how much risk is there from neonics? And how large are the benefits?

Second, here in New York, we have a governor and state agencies that are committed to ensuring our Pollinator Protection Plan (PPP) is more than just a list of guidelines. In addition to surveying wild pollinators, improving habitat, working with beekeepers to improve management practices, and many other actions, there is real money being put toward research on poorly understood or controversial topics, including pesticides. Since the state’s PPP was initiated in 2016, New York has allocated $1.2 million to applied research so we can improve our understanding of factors shaping pollinator health. And that includes neonicotinoids.

Why is this report unique? The scope of the report is limited to direct economic benefits to users and risk to pollinators. Thus, it is intended to complement existing studies and risk assessments, particularly the comprehensive reviews of neonicotinoid active ingredients conducted by the U.S. Environmental Protection Agency (USEPA). At the same time, the report is unique (and hopefully useful for policy makers!) since it summarizes new analyses and quantifies benefits to users and risk to pollinators in a side-by-side manner for the five major application contexts in which neonics are used: field crops (corn, soybean, wheat); fruit crops (e.g., apple, strawberry, blueberry); vegetable crops (e.g., squash, pumpkin); ornamentals, turf, & landscape management (e.g., golf courses, ornamental plant nurseries); and conservation & forestry (e.g., control of hemlock woolly adelgid in forests).

OK, let’s get to it. What did we find regarding risk to pollinators? For risk, lots of exposure data exist for field crops, while less is known regarding neonicotinoid exposures in tree fruits, vegetables, and turfgrass & ornamentals settings. And no exposure data exist that are relevant to pollinators in conservation & forestry settings. This means we have better insight about risk in field crops compared to all other settings.

Taking an LOEC approach to quantifying risk (i.e., using Lowest Observable Effects Concentrations from the peer-reviewed literature for neonic impacts on honey bees to set the bar for what’s defined as risk), the 4-panel figure in Figure 1 shows when risk occurs in each setting. All the blue data points above the red line indicate risk, while all the data below the red line indicate no risk. In and near corn and soybean fields that are planted with neonicotinoid-treated seeds, 74% of exposures are likely to impact honey bee physiology (cellular respiration), 58% of exposures are likely to impact honey bee behavior (worker memory and foraging efficiency), and 37% of exposures are likely to impact honey bee reproduction (egg laying and survival of new queens). With 96 exposure assessments, we have high confidence in these results; risk from neonics is often high in field crops settings.

Risk can also be high in other settings, but less data exist (i.e., there are fewer blue data points compared to field crops in Figure 1). Therefore, we have less confidence about conclusions regarding risk in these settings. This is an important conclusion in and of itself; we actually don’t know much about risk to pollinators from neonicotinoid insecticides in most application contexts because few studies have quantified exposure in these contexts. In other words, while there are literally hundreds of studies that have assessed hazard from neonics (i.e., studies that dose bees with neonics and assess how those doses impact mortality, reproduction, behavior or physiology), surprisingly few studies have assessed exposure to bees in the settings where neonics are used. Since risk is the product of hazard and exposure, we’re therefore often limited in what we can say about risk without knowing more about exposure.

That said, there are three additional take-home messages regarding risk. First, risk from neonicotinoids used on cucurbits (e.g., squash, pumpkin) result in exposures that are likely to impact honey bee reproduction in 85% of cases. The USEPA has recently recognized the high risk of neonicotinoids in cucurbits, issuing a recommendation to prohibit use of imidacloprid-, clothianidin-, and thiamethoxam-based products on cucurbits between vining and harvest to protect pollinators. Our analysis extends this window before the vining stage, since applications before or during planting (i.e., treatments applied to soils before seeding or at the time of transplanting) result in exposures known to impact honey bee reproduction.

Second, exposures in ornamentals (i.e., flowering plants in nurseries) are likely to impact honey bee reproduction in 70% of cases. While this conclusion is based on only 18 exposure assessments, the results are likely indicative of broader patterns given the widespread use of neonicotinoids on ornamental plants at nurseries.

Finally, it’s important to note that each neonicotinoid insecticide is not created equal. Specifically,   ….

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