Getting started with our conservation webinar,
I’m Holli Kuykendall, National Technology Specialist for NRCS’ East National Technology
Support Center. I’m pleased to turn the webinar over to Dr. Bill Hohman. Bill is a
wildlife biologist on the National Wildlife Team and he’s located in Ft Worth, TX. Bill,
you may now begin. Thank you, Holli. Hello. Thank you for your
participation in today’s webinar. It is my distinct privilege to introduce today’s
speaker, Dr. Christy Morrissey. Dr. Morrissey is an Associate Professor of Biology in the
School of Environment and Sustainability at the University of Saskatchewan. Her research
expertise is in avian ecotoxicology, aquatic ecology, ecophysiology, and wildlife conservation.
Christy has 18 years of experience working on issues related to environmental contamination
and the use of birds as indicators of environmental change. She has published over 50 journal
articles, book chapters and reports. She has been an advisor and member of the International
Union for Conservation of Nature’s Task Force on Systemic Pesticides and works closely
with provincial and national governments on regulations pertaining to pesticides, wetlands
and the conservation of migratory birds. Dr. Morrissey has been featured very broadly in
national and international media including the Canadian Broadcasting Corporation’s
Quirks and Quarks and The Nature of Things, Audubon Magazine, Science Daily, and a full-length,
feature documentary film about songbird declines called “The Messenger” that was released
in 2015. Welcome, Christy. Delighted to have you!
________________________________________ Thank you very much, Bill. I appreciate the
invitation and the chance to speak to a sizable audience about our work. I will jump right
in and get started. Basically, I am going to talk a lot about our lab’s work which
is a collective effort and certainly what I am presenting, some of it is published and
I have provided some handouts of key publications as part of the webinar. I am also presenting
some unpublished data and hopefully that will be out fairly soon. A lot of what I am acknowledging
is the result of hard work by my graduate students who have been key in collecting this
data. Most of you are familiar with the controversy
around neonicotinoids and bees. Certainly, bee studies have been central to this neonicotinoid
debate that has been going on for several years now. Most of the studies were initially
focused on bee mortality, especially mortality events that occurred after planting. There
was also some interest in whether neonics were a potential cause of the colony collapse
disorder. Later studies have now become more focused on sublethal effects on bees. This
has become prominent in the literature. As you can see in this graph, there has been
a rapid rise in the science of neonicotinoids since they were brought on the market in the
early 1990s. So, this is the number of papers that have been published based on a quick
Web of Science search. You can see there has been a rapid increase year on year. To date,
we now have over 2000 papers that have been published on this topic. Of course, not all
on bees. There are plenty more papers on this topic.
The bees are important. They are central to the controversy and the issue. There has been
quite a bit of debate and interest about bees but it’s really not just about bees. I think
that I could have made the title of this webinar, “It’s not just about bees”, but I didn’t.
So, here we are. Neonics can contaminate whole ecosystems and
the bees are part of the story. They are a key part but there are whole other components
that neonics are affecting. In particular, neonics are affecting soils, surface water,
groundwater and other nontarget organisms that are important to functioning ecosystems.
I am going to talk a little about that and get into that a bit through this webinar.
So, why is the water issue and the soil issue so important? Well, it really starts from
the way that neonics were designed. By nature they were designed to have these three key
properties that help them to be useful as a plant systemic, but they also create environmental
issues. The first is that these have an extended half-life in soil. For example, the half-life
in soil for clothianidin (DT50) is in the range of 13 to over 1300 days. This is years
these can persist in certain soils under certain conditions. They also have very high water
solubility. This is quite unusual compared to most other insecticides that are on the
market past and present. For example, water solubility of thiamethoxam, which is the most
water-soluble neonic compounds, is 4100 µg/L. What does that mean? If you compare it to
some of the other organophosphate or pyrtheroid insecticides this is orders of magnitude more
soluble. In contrast, solubility of chlorpyrifos is just 1.4 µg/L and diazinon (which has
been banned) is 40µg/L. Cypermethrin is also not very soluble at all. In fact, it binds
tightly to soil and does not move. This is an important feature. They are also stable
in water. Many pesticides breakdown in water through a process known as hydrolysis, but
neonics do not undergo hydrolysis. They are stable. They need UV light to break down through
a process known as photolysis. It can be a highly variable on how efficient or how quickly
they break down when they are in water. It depends on the turbidity of the water. Whether
the neonic gets near the sediment layer. Whether there is any plant or algal cover over those
water bodies. How quickly neonics degrade depends on many factors.
Neonics are widely used. There is not a crop that you can list that neonicotinoids are
not approved for. The figure on the left from Doyles and Tooker (2015) shows why we are
seeing the rapid increase in neonicotinoid use is mainly due to widespread adoption of
seed treatments in maize and soybean crops that you are probably familiar with. On the
right, here’s the map for the U.S. estimating use of thiamethoxam, one of the key neonicotinoids
used across the Continental U.S. The same pattern is true throughout North America and
in fact worldwide because these are the major crops and neonicotinoids are applied as seed
treatments or foliar spray to most of those crops.
What kind of evidence do we have that these things are getting into water? I could spend
the whole webinar talking about water contamination. I will try to summarize it a bit for you here
because there has been an extensive amount of work in my lab and others around the world
that have found high frequency of detection in surface waters and more recently in groundwater
and even in drinking water after treatment. This frequency of detection is what is alarming.
There is repeated and chronic contamination of surface water. That is, because these compounds
are so persistent in the environment, as soon as there is rainfall or anything where you
have more water on the ground (e.g., through irrigation and other processes), you get frequent
and repeated contamination of water bodies. The exposure profile for anything that is
in water is chronic rather than the more typical acute scenario which would be for most other
insecticides. There is actually no specific association with crops or uses that have been
found to date. So, water monitoring data that has occurred has not been able to pinpoint
one or two smoking guns. It’s not one or two uses. It’s not just greenhouses or just corn
or whatever. The inability to precisely pinpoint sources of contamination causes an issue with
regulation of these chemicals. Finally, here in the northern climate where I’m from in
Canada, we have found that snowmelt water and run-off are the primary sources of spring
contamination of water-bodies even before planting, even before seeding and application
occurs. Because they are persistent in soil through the winter, you get neonic contamination
of wetlands early in the season that’s often unexpected. So, all of these things combined,
create a pattern of water contamination that is widespread.
Here is data from our lab over three summers (2012-14) in Prairie Canada. These measurements
were taken in Saskatchewan which is in the center of the Canadian prairies. I am showing
here mean concentrations in wetlands of each of the different neonics and a black bar which
represents the sum or total concentration of neonics found in wetlands during the three
summers. If you try to think, “What does this mean? Well, it turns out we have come
up with a chronic aquatic toxicity threshold or reference value of 35 ng/L that would be
considered safe. You can see most of these bars exceed that threshold. In fact, we know
that on average 50 to 60% of wetland samples are exceeding that threshold level.
We cannot discern where it is coming from. There are many crops that are using these
compounds. We found that barley, canola and oats all have higher concentrations than grassland
or hayland, but you can see that they are really present everywhere. So, they are consistently
found in a range of prairie crops. We did the large-scale summer water sampling
in an attempt to cover a wide geographic area as well as a large range of crop types, landscape
gradients, soil gradients, water gradients etc., that occur in the province of Saskatchewan.
This is data that we collected from 140 wetlands or ditches across 16 different sites. We get
the same pattern; that is, all four neonics show up. Acetamprid is very rare. The top
three are thiamethoxam, clothianidin, and imidacloprid . On the top of those bars is
the percent detection. It is typically about half for each of the compounds, but when you
put them together we are at upwards of 76% of wetlands have at least one of the neonics
in it.. On the far right you have TEQ neonics or the toxic equivalency. We have done some
work to better calculate what we should do when more than one neonics is present and
this in the toxic equivalency relative to imidacloprid.
Neonics are not all the same. We have been regulating them primarily based on data from
imidacloprid. Unfortunately, it’s difficult when you have multiple neonics out there.
“What you do?” They may act the same way or they may not. We have done work with larval
midges. Chironomus dilutus is our model test organism. It is a species that is found in
prairie wetlands and, indeed, in many parts of North America and Europe. So, it is a very
ecologically relevant species. We have done chronic aquatic lab studies with this species
looking at three different neonics. On the top of this figure we have thiamethoxam, in
the middle we have clothianidin, and at the bottom is imidacloprid We have actually found
that neonics vary in their toxicity. The left side is total larval abundance and on the
right side is the proportion of the adults that have emerged. You can see thiamethoxam
is the least toxic. Even at our highest dose of 10 µg/L which is pretty darn high, you
still get something coming out of the water and, although overall abundance is reduced,
you still see some emergence and survival. For clothianidin and imidacloprid survival
and emergence is quite a bit worse in those scenarios. We can rank the toxicity of these
compounds. Whereas thiamethoxam is the least toxic, clothianidin and imidacloprid are similar
with toxicities that are ten-times higher than that of thiamethoxam.
We’ve also found important sublethal effects. In addition to survival and abundance, we
also looked at timing of emergence and we saw effects at much lower levels. We also
see biased sex ratios with treatments producing a male biased sex ratio (i.e., more males
than females). Something may be going on there that is affecting females more than males
at low concentrations. It is important to look at these sublethal effects which can
be relevant in a natural environment. Some of the questions we have thought about
over the years is these things are not simply showing up by themselves. It’s not just one
neonic. If they vary in toxicity individually what happens when you put them together? About
70% of the detections from this broadscale sampling were mixtures, so we think that mixtures
should probably behave additively in the organism based on their similar mode of action.. The
default thinking is that they will be additive in toxicity, but that may or may not be true.
By additive, I mean that if I’ve given you a mixture of .5 µg/L clothianidin and.5 µg/L
of imidacloprid , then you should expect the same response as one µg/L of neonic. But
we don’t know that. We have been doing work on mixtures. This
is work done by Erin Maloney pictured on the right. She’s my PhD student who came up with
this fixed rate experimental design that uses a mixed path approach, so it’s a regression-based
approach that is more powerful and allows you to test a wide range of doses both in
terms of ratios of different neonic combinations as well as dose concentrations or dose levels.
It is based on the toxic unit approach. She’s done binary mixtures as well as tertiary mixtures
with all three neonics. This is fairly complex data. This is an acute toxicity study in which
we only expose midge larvae for 96 hours. I will show you the snapshot of the results.
We can compare the response of a mixture with what we know as reference models for four
different scenarios that we would expect. These are 3D binary mixture dose-response
surfaces that give you an idea what we could expect when we compare the actual data to
these modeled data. On the left is the clothianidin-thiamethoxam actual response of the organisms when we expose
them over this plane or array of different doses and dose ratios for the two compounds.
In essence, this combination causes weak synergism. So it actually matches the synergism model
statistically. We find that for all the combinations – they are all weakly synergistic. That is,
the combined effect is greater than additive toxicity.
We can move out of the lab and start thinking about, “What’s actually going on in the
field?” We want to know what’s going on in the real world because of criticism about
the generality of lab studies. What’s going on with bugs and are they really affected?
Working in the real world adds complication. I’m a big fan of working in the field. We
sometimes have to go somewhere in between in order to get conclusive results. Michael
Cavallaro, one of my PhD students, developed this limnocorral study where he deployed 21
of these custom-made, wetland limnocorrals. They are 1 m x 1 m in width and their depth
is about 1.5 m. The sides of the device have enough slack in them if the water-level goes
up or down the limnocorral floats to adjust up and down. They are anchored to the sediment.
We were able to test very similar to what we did in the lab. We tested three different
treatments for three neonicotinoids: clothianidin, imidacloprid and thiamethoxam. We were able
to do it at two different dose concentrations,.05 and .5 µg/L. These are low concentrations,
very much in line with what we see in the field, this is kind of average levels that
we might see. They are relevant, not high concentrations that would hit the organism’s
hard. We measured neonicotinoid concentrations throughout the experiment. We collected insects
from corrals every 3 to 4 days and monitored these over eight weeks of dosing and a further
six-week recovery period where dosing ceased. What did we find? Data from these experiments
is complex. We’re looking at community data, that is multiple invertebrate species that
are emerging out of these limnocorrals throughout the season both during the dosing and recovery
periods. The graphs on the right represent the three different neonic treatments. There
were replicates within each treatment and there’s a high and low dose. Responses to
the high dose are shown with solid symbols and solid lines; low dose with open symbols
and dashed lines. What you are looking at is where these lines change relative to the
control. The control would be the zero line across the middle. You can see for imidacloprid
during the dosing period, there’s a shift up in the whole community from the zero line.
That shift is significant. We see more multivoltine species occurring and there was a shift away
from what the controls actually looked like. The clothianidin treatment also had a shift.
It was in the downward direction but it was not formally significant because a large amount
of variation in the treatment corrals. For thiamethoxam we did not see a treatment affect.
Invertebrate responses to the thiamethoxam treatment were similar to the control. All
of the treatments seemed to recover within two weeks after dosing to near or at control
community. It suggests that these systems can recover, but I would like to add that
these limnocorrals were placed in clean ponds. We had the tops off at regular intervals and
so recolonization of the individuals back into the corrals was certainly possible throughout
the experiment. So it is possible that recolonization was driving the recovery.
We also note in these corrals that for chironimids, the test organism of choice and also the most
numerous organism in the corrals, that their emergence occurs significantly earlier, which
is not something we expected or something we hypothesized. We thought emergence would
be later or delayed. In fact, we see this both in the lab and here in the field. That
chironomids exposed to clothianidin and imidacloprid and to some extent thiamethoxam are emerging
seven 7 to 11 days earlier compared to the controls.
This slide provides an overview of what’s going on with invertebrates. Well, certainly
they are sensitive. Most are affected by neonics at varying concentrations. We have looked
at 49 species which are contained in over 200 lab studies that have been published or
unpublished. Some of these are government and industry studies. We have plotted the
species sensitivity distribution which shows you get this very wide range in sensitivity
between the most sensitive species on the bottom left to the least sensitive at the
top right. The key thing that you will notice is that insects which are the red dots are
much more sensitive than crustaceans on average. Of interest, perhaps, people have said to
me, “How did these compounds get registered for use, if there are so many of these species
that are sensitive at low concentrations?”. Most of the testing was done on this circled
organism on the top right, Daphnia magna. You can see Daphnia magna is insensitive to
neonics. You might assume or conclude that neonics are not a problem to invertebrates
if you only test species like Daphnia. Whereas Chironomus dilutes, the test organism that
we use in the lab is down there on the far left.
What amounts of neonics are safe in water? That depends on who you ask or what country
you ask. These are guidelines that have been published for various countries around the
world or various regions around the world. The least conservative guideline is the US
EPA which is sitting at 1.05 µg/L (average) or an acute exposure of 35 µg/L. I will talk
about how they are in the same boat as Canada in looking to revise that value, but that’s
where it is currently. Canada’s current guideline was.23 µg/L. You can see that once you look
at the European guidelines and the Netherlands in particular and recent published studies
including our own, these are getting much lower. We are now starting to look at data
that’s out there and suggest the guidelines need to be much, much lower than what they
are. So in the range of .035 µg/L for chronic or average exposure and Canada’s PMRA has
recently proposed new guidelines for imidacloprid of .041µg/L. That is close to the value we
published the year before at .035µg/L. When you look at what’s going on in the real
world in terms of how many monitoring studies are out there, we did evaluate what concentrations
there are in water around the world from published studies . We found out that of 27 studies
that reported peak concentrations of neonics in water, 22 of those or 81% exceeded our
acute threshold of .2 µg/L or 200 ng/L. If you look at the chronic studies, those that
have looked at neonics concentrations over time and produced average concentrations,
14 out of the 19 studies or 74% report data that exceed our published threshold of 35
ng/L that we think should be considered safe. You can see it is widespread that water concentration
are exceeding guidelines for safe levels for aquatic invertebrates.
What does this all mean for protecting our wetlands? Neonics are frequently detected
in wetlands, often as mixtures that are synergistically toxic when they are co-occurring. Concentrations
exceed the threshold where sublethal effects are expected on sensitive individual species
such as mayflies and true flies like chironomids. We do see community shifts as well as shifts
in the phenology or timing of when these insects emerge out of the water. These can occur at
low concentrations under chronic conditions and that is really relevant in the natural
environment. We do see that recovery seems to be possible, but that assumes that recolonization
is available to those waterbodies. If everything in the surrounding region is contaminated,
you may not have the same degree of recovery. Current water regulations in North America
are not protective of aquatic organisms. Those listed here are for the CCME as well as the
US EPA. These are now shown to be not protective. There are proposed new guidelines for Canada
and the U.S. that are moving towards more protective threshold levels. You will have
to stay tuned for that. Why do we care about losing a few bugs? I
hear that a lot. “So what about a midge or a mosquito?”. It’s because the things
that eat these sensitive aquatic insects are birds and other wildlife. I think we have
to extrapolate on what’s occurring in terms of a few bugs to what’s occurring in a whole
food chains. There was a nice study published in Nature
in 2014 by Hallman et al.. They looked at 15 farmland bird species in the Netherlands
where they have good data for over 20 years on imidacloprid concentrations in water as
well as bird data. They were able to do this analysis that you can see on the map there
are differences in concentrations of imidacloprid in surface water — the red or hot colors
is where there’s higher concentrations and they also had lower concentrations in other
parts of the country. They found on average a 3.5% decrease in the average number of those
insectivorous farmland birds in areas where imidacloprid exceeded 20 ng/L or .02 µg/L.
If you recall, that 20 ng/L is pretty close to the number (35 ng/L) that we found or published
in our review that said that would be a safe level for aquatic invertebrates. There seems
to be some evidence that this is a relevant number and that food chains including birds
are affected at higher water concentrations. Here in Saskatchewan we’ve done studies with
tree swallows, which are a model aerial insectivore. We found that adults and nestling tree swallows
are highly dependent on aquatic insects. On the stable isotopes plot, here this is work
done by Master’s student – Chantel Michelson, adult swallows were almost wholly dependent
on aquatic insects and nestling swallows a little less so. But both groups, throughout
the breeding season are highly dependent on these aquatic orders and really not using
terrestrial prey much at all. We also see that there are hints that in certain
years there is a mismatch in the timing of peak food availability. This may be a clue
that phenology is important for when these insects are emerging out of wetlands. If those
are affected by neonics, even a delay of 10 days can throw birds off quite a bit, because
birds are timing their clutch initiation and their hatching dates for when peak food availability
is occurring. On this slide, we show that the agricultural sites here have a mismatch
in the peak insect abundance relative to the clutch initiation date, whereas the grassland
site has a very well matched clutch initiation date to peak insect biomass. We are starting
to explore this more to see how frequently this occurs between years and how this relates
to the neonic concentrations in the wetlands. We also note that swallows at crop sites must
forge more aggressively. They have to spend more time away from their nests. Both males
and females spent more time away from the nest presumably foraging at the intensively
cropped sites than at the grassland sites. The consequences for nestlings is that at
sites where there are intensive crops using neonic seed treatments, those chicks have
lower body condition. This is circumstantial evidence that points to the fact that these
systems are not as productive and possibly because of the reduction in aquatic invertebrates.
How can we mitigate against these pesticide effects on wetland agroecosystems? This is
a huge question, “What do we do?” I will spend the last little bit here talking about
this question. In order to mitigate, you still need to know what factors influence the fate
and persistence of neonics in wetlands. You need to know what is driving them. So I will
give you a few little hints from the work that Anson Main did as part of his Ph.D.
Where you look at these two canola fields (you can see in the background the yellow
of the canola just emerging), you have different concentrations of neonics in the waters of
these wetlands . What’s driving that? We will try to explore that?
We’ve done extensive work coming up with a wetland assessment process and analyzed over
250 prairie wetlands and looked at the structure of these wetlands, a whole range of vegetation
criteria, landscape, hydrology, hydrogeomorphology and the wetland class to try to identify features
or factors may be driving neonics concentrations in these wetlands.
The main finding is that temporary and seasonal wetlands are the most susceptible to neonics.
Permanent and semi-permanent wetlands have lower neonic concentrations.
When we do this large what we called boosted regression tree analysis, it allows us to
put many variables in the same model and test which ones are more important in predicting
water concentrations. We interestingly find that the top factor that comes out in these
models, both for affecting concentrations in the water, associated with higher or lower
concentrations as well as detection probability, tends to be things like the shallow marsh
species composition as well as wet meadows species composition. There are other factors
like the crop and depth of the wetlands in the area but we were surprised to see vegetation
can play such an important role in predicting what is going on in these wetlands.
To give you a snapshot here’s what it looks like, these plots on the left show marginal
effect on neonicotinoid detection probability. Here we are ranking which plant species in
the shallow marsh are associated with higher detection probability at the top versus low
detection probability at the bottom of the figure. You can see some species (e.g., field
pennygrass and salt marsh bulrush) are associated with high neonic detection and some plants
(e.g., Bebb’s sedge and wheat sedge) are associated with low concentrations. In the
middle, we do look at “none”. My pointer is showing this “none”. We see there is
no plant material, so the buffer has been removed all together. It’s only associated
with no real effect, not positive or negative neonic concentration. So, the buffer alone
is not what’s doing it, it’s the plant species composition.
Vegetation disturbance in general is important. If you disturb wetlands more than 25% you
see this rapid increase in detection probability. Again, above 45-50%, you see another jump
in higher detections. Intact wetlands seem to be buffer pesticide
contamination. This is an interesting fact that we are exploring now. How much can vegetative
buffers help? It seems that if we look at wetlands with and without vegetative buffers,
those with the buffers have lower concentrations of neonics. Width of buffer does not seem
to matter. So we found no association with buffer width. It’s just whether it’s present
or absent that seems to be at least a partial driver.
We have been exploring whether or not wetland plants can reduce the amount of neonics in
the water or moving into the wetlands through accumulation in their tissue. In analyzing
these different species of wetland plants that are commonly found, we find that some
of the plants are able to take up neonics and we see detection probability for example
in this Horsetail that is around 78% detection frequency. Here on the left, just for comparison,
is a treated canola plant which you would expect to have 100% detection frequency and
it does; however, even some of the common wetland plants are between 50 and 80% detection.
Here is a snapshot for you to take away and start taking about. What we are finding is
widespread water and soil pollution that seems to be unavoidable given the magnitude of use
patterns, particularly for seed treatments which are often used prophylactically. These
compounds are so water-soluble that the motility, their movement off the seed and off treated
soils, is substantial. That combined with their long-term persistence both in soil and
water and repeated applications (e.g., corn-on-corn or canola-on-canola), you will see very high
rates of detection in water-bodies. There are negative effects to sensitive invertebrate
species. Also community diversity was affected. This is particularly from imidacloprid and
clothianidin; thiamethoxam seems to be less problematic on the scale of things. There
are direct and cascading indirect effects to wildlife. In particular, I’m talking about
birds here because that’s what we have studied. These potential effects on birds are important
for regulatory decision makers to consider. What do we do? We need to identify ecologically
sensitive aquatic ecosystems. Those that are important to us. Those that harbor important
birds and wildlife species. We need to completely avoid using neonicotinoids in these watersheds,
not just surrounding fields. That’s because we are seeing neonics in groundwater, even
in grassy areas, which we cannot trace an immediate source which suggests that it’s
coming from distant sources. You need to identify those places where they should not be used
and avoid using them in those watersheds altogether. Finally, plants matter. Using plants to restore
wetlands and mitigate for the effect of neonics can be a useful strategy. An important fact
here is not just putting a buffer in, which is helpful, but actually putting in a buffer
which consists of diverse vegetation (i.e., macrophytes) that seem to be important in
reducing the contamination problem. I can’t leave without telling you that agriculture
needs a redesign. It’s not swapping one chemical for another chemical. We need to
incorporate ecological intensification into these systems by reducing soil disturbance
and focus on soil quality. Cultivate a wider range of species through a variety of methods,
e.g., cover crops, perennial crops, intercrops, etc. Introduce more varieties of crops into
these systems to increase system resilience. Using integrated pest management which has
fallen away in the favor of using more pesticide products to control disease and weeds and
pest problems. We need to go back to that. Finally, maintaining and restoring wetland
and riparian buffer areas and use water efficient crops. Really focus on enhancing these wetland
areas which we are starting new work to see whether or not wetlands can buffer or offset
some of the damage of agriculture. A final thank you to the many people who do
this work, particularly my graduate students and the key collaborators that I have listed
and our funding organizations. With that I will take questions that Bill
will moderate. Thank you very much. That was wonderful presentation. Thank you.
We did get some questions. First one, “Is there any indication of bioaccumulation or
physiological effects on primary consumers or secondary consumers? The question is, “Is there accumulation
of neonics in the consumer organisms, both vertebrates and invertebrates?” In short,
we don’t know. There is a little bit of data out there and in fact we are doing a study
now to look at accumulation in insects. We believe it is fairly low, but there has been
one study done by Mark Bélisle’s group on swallows where they were able to detect
neonics in insect samples. So, we think that it can occur simply because these compounds
bind to the receptors. There is a biological basis for assuming they can accumulate to
some extent; however, these are not like the organochlorines that build up in tissues.
We don’t really know about other vertebrate consumers at this point. In insects, it’s
probably not a huge issue because it kills them or causes a major affect before they
can be passed on to the next food web level. What is the fate of those neonics that are
taken up by the plants. Wetlands are primarily detrital-based systems. If they persist in
the plants past senescence does that further expose aquatic invertebrates to neonics ? It’s a double edge sword. The plants are
able to take up the neonics. That’s great for the water organisms that are that are
potentially less exposed but what about those species that are using pollen or perhaps even
eating the whole plants. We don’t know anything about the exposure for organisms that are
using wetland plants. That is something we want to look at because it is an important
factor. We know muskrats and other things nibble on these plants. Many pollinators use
wetland flowering plants as a source of pollen. So, it is not without its issues that these
plants can accumulate them. In addition, plants do die off at the end of the season. To what
extent compounds in dead plants are remobilized back into the water, we do not know, because
we are not sure how much plants are metabolizing the compounds before they die off. We received a question related to risks to
pollinators, so thank you for that detailed response. How do these mixtures come about?
Is it a result of different cocktails being applied to seeds or different applications
to crops in agricultural watersheds? It’s a combination. Our most common mixture
that we see is clothianidin and thiamethoxam. That mixture is telling for two reasons. One
is, those two compounds are the most widely used in this region, e.g., . it’s the most
widely used on canola. The cereals often are using thiamethoxam and in the U.S. corn seed
treated with clothianidin would be the most common. This type of mixture is common because
of use patterns, both field rotations as well as neighboring fields, e.g., one field has
a seed treated with thiamethoxam and one has a seed treated with clothianidin. So, there
is that. The other thing is that thiamethoxam’s major breakdown product is clothianidin. Although
I did not mention that in the presentation, a key point about thiamethoxam having lower
toxicity to organisms is that we were not allowing those systems to breakdown thiamethoxam
and be exposed to both compounds. When thiamethoxam breaks down to clothianidin the organisms
would now be exposed to a more toxic, more persistent compounds. You see these mixtures
occurring in the field and it’s likely that there is some metabolism that occurs in the
field that is influencing that mixture. Certainly, that mixture is synergistically toxic when
the organisms are exposed to it. Are nestlings more susceptible to predation
when adults are away from the nest foraging? Yes, absolutely. In this study, because we
use nest boxes, the predation rates were low. However, if you were to extrapolate that to
other non-nest box species, I would anticipate that lower nest attendance rates would be
problematic and have been shown to be problematic in many ecology studies, e.g., higher predation
rates, killing of the chicks, lower growth rates, etc. There are lots of knock-on effects
that can happen when you spend more of your time away from the nest. Is it your sense that the effects of neonics
on secondary consumers like birds is primarily due to reduced food availability or direct
toxicity? I’m showing here that birds are indirectly
affected through the food web. That is, changes of timing in emergence and the changes of
abundance in emerging insects being a factor affecting insectivorous birds. There is another
group of birds, the grassland birds, that are primarily seed eaters and spend a lot
of time around farmland areas. Many are specialists in farmland areas. We have done some dosing
studies with seed eating birds to look at direct effects of consuming the equivalent
of a few treated seeds. We see very severe effects of imidacloprid on those songbirds
including mass loss and orientation and migratory behavioral changes. These are significant
but affecting different species. So, there are problems for the invertebrates food chain
as well as the seedeaters that would consume seeds in treated fields. As you know, in the U.S. many intensive agricultural
areas particularly in the Upper Midwest, have subsurface drainage. Do wish to comment on
risks to aquatic systems posed by surface versus subsurface runoff? Wish I could answer that more authoritatively,
because we don’t have any tile drained farmlands here in this region of Canada. So, I have
limited experience and none of our personal data to refer to. You would expect tile drains
to be enhancing the amount of groundwater contamination and movement. The one thing
about groundwater is that runoff is not exposed to light. You get no degradation from a fairly
large area where the drainage is occurring. It will degrade once it hits the wetlands,
but that’s already now more concentrated. I think tile drains is an area that we need
to explore seriously. I’m not aware of any studies that have looked at wetland contamination
in tile-drained versus non-tiled areas. I know that there was study recently published
that showed high levels in some of Iowa’s aquatic systems. Yes, there is a general study that showed
high levels, but no specific comparisons between tile drained and non-tile drained areas. I
would expect that tile drainage would increase neonic concentrations in aquatic systems . There are a few related questions. Are fish
or amphibians affected by neonics? The short answer is no. The longer answer
is food web effects could still potentially be there. There were some hints of that in
a new study that came out by Stacy Robinson looking at the effects of neonics on amphibians
and wood frogs in mesocosm. The dosing concentrations were not realistic, but you do see changes
in the food web and consequences for the frogs. In this case, there was a positive response,
because they got a lot of zoo plankton production (e.g., cladocerans) that the tadpoles fed
on readily. Frogs did well under those scenarios, but these things are difficult to predict
for every species. Direct toxicity does not seem to be an issue for most fish and amphibian
species. Sublethal, long-term contamination could affect the food web and potentially
affect subtle end points related to immune systems that we haven’t looked at yet. A participant observed that sublethal effects
that you reported here for seed-eating songbirds (i.e., confused orientation) are similar to
sublethal effects of neonics reported in bumblebees. One more question. Is it correct to assume
that neonics replaced some earlier class of pesticides and, if so, what were those and
what do we know about comparative toxicology? Neonics were brought on primarily
to improve upon organophosphates, an extremely diverse group of chemicals (e.g., chlorpyrifos,
diazinon, malathion, etc.), many of which are still available on the market today. Neonics
were brought on because many of the organophosphates were acutely toxic to vertebrates including
humans. There were studies linking organophosphates to increasing rates of ADHD in children and
other developmental problems in farmworkers and their families . That was part of it.
The other thing was that the other class of pesticides, pyrethroids, did not work very
well, although they were much less toxic to humans and wildlife. Neonics were this amazing
new development that you could apply as a seed treatment or systemic that would be taken
up by the plant. You could apply them in low concentrations. They were not toxic to vertebrates
including humans. It was a great idea, but not well thought out in terms of these larger
environmental issues we know today. Let’s leave it there. Thank you for a wonderfully
informative presentation. Thank you too for sharing your cutting edge research on this
important topic. [Oops, one more.] Is it your sense that seed coating for the delivery of
pesticides and fungicides is the direction that agriculture is going? Maybe I should
be answering that. It seems that the direction that agriculture is going is towards the delivery
of chemicals by means of seed treatments. Yes. The current paradigm in agriculture is
now to purchase your seed. The seed is owned by chemical companies and the seed has the
chemical on it. The fungicide and insecticide are on the seed. You buy these actually the
year before you use them. You buy the treated seed in the fall well before you know what
your pest problem is. That is the direction that agriculture has gone. I think that’s
one of the fundamental flaws here. The idea of having a targeted treatment has been perversed
in some way towards now using it everywhere on everything whether it needs it or not because
it’s convenient way of applying your chemical. Thank you again Christy Morrissey
Thank you for the invitation and the chance to speak to this group. I want to thank you Christy Morrissey. This
was an informative presentation and a pleasure working with you. It was also a pleasure working
with you, Bill. Thank you all that you do to educate our participants. We had more than
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