>Why does the plant need more "leaf protection" later in the season?

The neonics are effective insecticides, of a different mode of action than
other classes.

Their strong point is their ability to move systemically, with their best
use to be as seed treatments, drenches, or injections.

But that doesn't mean that they can't also be used as foliar applications.

There are pests that have developed resistance to pyrethroids, OPs, and
other insecticides on the market.  Foliar neonics may be effective in
controlling them.

But there are indeed several concerns for pollinators with foliar
applications, and to me, with the allowable tolerances in the petitions.

I spent an hour in a conference call to the ecotoxicologists at Syngenta
yesterday, asking them for answers, and then submitted the following
comments to EPA:

Re EPA-HQ-OPP-2013-075, EPA-HQ-OPP-2013-0758 by Syngenta Corp for new or
amended tolerances for thiamethoxam.

By Randy Oliver

ScientificBeekeeping.com

I am a commercial beekeeper and independent bee researcher, writing monthly
for the American Bee Journal, maintaining the website
ScientificBeekeeping.com, am deeply involved in pesticide issues, and have
amicably consulted with the ecotoxicologists from Syngenta about my
concerns.

 Regarding neonicotinoids in general, application by either seed treatment
or carefully controlled drench or injection appear to be the highest and
best usages.  That said, as EPA phases out the OPs and carbamates, and as
pests develop resistance to the pyrethroids, it is understandable that
growers are seeking foliar insecticides with other modes of action.
Foliar-applied
thiamethoxam is an option.

 *Crops of particular concern*

My concerns are with crops that are specifically known to be attractive to
pollinators, to wit from the petitions noted above:  alfalfa, sunflower,
buckwheat, corn (esp. sweet corn), soybean, and legumes.  Beekeepers are
quite concerned about insecticide applications to these particular crops,
as all but corn are important honey crops, meaning that both honey bees and
native pollinators stand a plausible chance of suffering unreasonable risks
from the use of foliar thiamethoxam applications.

Look at some of the requested numbers, keeping in mind that anything over
10 ppb causes some adverse effects in honey bees, and by 50 ppb causes
clear adverse effects:

Sunflower—400 ppb

Alfalfa—1000 ppb

Buckwheat and some legumes—900 ppb

 *Concerns about regulations re timing of applications relative to bloom*

It will be very important to have restrictions as to spraying not only
during bloom, but also during the time period shortly prior to bloom.  For
example, there is little or no data regarding the amount of a.i. that is
found in alfalfa nectar post foliar application of thiamethoxam.  Were a
grower to apply foliar thiamethoxam on alfalfa a week before intended
cutting, and then had the cutting delayed for some reason, thus allowing
the alfalfa to come into bloom, would pollinators suffer?


*Concerns about systemic transport into nectar and pollen*

Thiamethoxam, being systemic in the xylem, could transport to the nectar
and pollen not only of crops sprayed shortly prior to bloom, but also in
flowering weeds (and escaped alfalfa) along the field margins at the time
of spraying.  The Syngenta ecotoxicologists are under the impression that
such transport would be short term, and not affect new growth.  However,
that still leaves the concern with flowering immediately following
application.

Firm restriction of any foliar applications to only crops not in bloom, nor
expected to bloom within 2 weeks, would greatly help in reducing risk to
pollinators.


*Concerns about aerosol particles*

I also have concern about the residues from overspray on flowering weeds in
field margins.  There is preliminary data suggesting that neonics in
finely-aerosol form may be especially toxic to bees (pers comm).  We are
well aware of the adverse effects of thiamethoxam planting dust from corn
seeding; we must determine whether the drift of aerosols from foliar
applications may also exhibit unreasonable adverse effects upon pollinators.

*Concerns about seriously high allowable residue limits*

I understand why the high limits have been petitioned for, and that they
are not requests for higher *application rates*.  However, some of the
requested limits seem to be excessively high, e.g., 1 ppm (1000 ppb) in
alfalfa seed, and nearly that in buckwheat and legumes.  And an incredible
10 ppm (10,000 ppb) in alfalfa hay—which is typically cut right at the
beginning of bloom.  It is hard for me to imagine that alfalfa sprayed to
contain 10,000 ppb of thiamethoxam when typically cut right at the
beginning of bloom would not produce nectar acutely toxic to pollinators if
there were any delay whatsoever in cutting.  The fact is that many
beekeepers make a honey crop on alfalfa, so clearly a large amount of
alfalfa goes into bloom each season.


*Concerns about contaminated dust and residues on leaf surfaces*

Since the high-level tolerance levels are not from systemic action via seed
treatment, but rather from residues on the surfaces of the plant material,
that means that the actual residues on the surfaces of the seeds or hay
would be greater by at least an order of magnitude—e.g. 100,000 ppb.  These
are truly high levels of such a pollinator-toxic insecticide!  My concern
is that any residue-containing dust on the foliage or blooms could be quite
toxic to pollinators.  And we must consider any drift onto surrounding
vegetation, which could also wind up with such excessively high levels of
surface residues.

Such toxic surface residues require very careful measurement of RT25’s for
pollinators, supposing that EPA feels that a 25% kill of any visiting
pollinator species is not an “unreasonable risk to man or the environment.”


*Concerns about overuse or misuse*

Another concern with raising the allowable tolerances is that it removes
much of the incentive of growers to minimize their applications of the
products, since the “normal” check of products to meet human safety or
export requirements would be set to such high levels.  Such high tolerances
invite the misuse or over application of this insecticide by growers, who
today tend to apply insecticides more as risk management rather than by
actual need.  The lower limits created an effective check on over
application of systemic insecticides; I’m not sure that the raised limits
would.


*Summary*

In summary, I am not opposed to the requested tolerances, provided that
rock solid data exist for each crop, under normal field conditions, that
the registered applications required to reach those tolerance levels would
not create unreasonable risk to pollinators, both honey bees and native.  Such
data should be made freely available to beekeepers and the public.


-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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