[Pollinator] Killer in a Bottle? Household insecticides may play a role in declining bee populations

Wed Oct 24 11:36:33 PDT 2012

Killer in a Bottle?

Household insecticides may play a role in declining bee populations

http://www.cfans.umn.edu/Solutions/Fall2012/Killer_Bottle/index.htm

By Becky Beyers

Bees.

Vera Krischik

Vera Krischik's lab tested how bees would respond to applications of
neonicotinoid pesticides on ornamental plants such as roses.
Photos by David Hansen

Vera Krischik and her lab in the Department of Entomology
<http://www.entomology.umn.edu/>  are exploring a different avenue: how
neonicotinoids, a group of insecticides commonly used in urban gardens and
forests as well as in agricultural fields, might be making bees less
resistant to the parasites and pathogens that researchers now believe are
likely causes of Colony Collapse Disorder.

Infesting the system

About two-thirds of the world's crops rely on bees and other pollinators; if
the bees are gone, so are the fruits, vegetables and other plant-based foods
they help create.  

Other insects are less beneficial, however, so farmers and gardeners turn to
insecticides to protect their crops. The first neonicotinyl insecticide,
imidacloprid, came on the market in the 1990s. Since then, three
more-thiamethoxam, clothianidin and dinotefuran-have been registered for
use. All have similar toxicity to bees and all are commonly used in
Minnesota: in 2009, more than 8 tons of insecticides primarily using
imidacloprid and nearly 10 tons of clothianidin were used on farms and
nearly another ton of imidacloprid was used on the state's landscapes. When
it was first introduced, imidacloprid was considered a breakthrough because
it wasn't harmful to humans or mammals, and they're now extremely popular.
"Most people didn't realize that this is a systemic insecticide," Krischik
says.

Imidacloprid is commonly sold to farmers as Admire, Provado and Gaucho and
to businesses and home gardeners under names Merit, Marathon, Bayer Advanced
Flower and Shrub, Bayer Tree and Shrub Protect, Bayer Complete Insect Killer
for Turf, Krischik says. When neonicotinoids are applied to a field or
garden, the chemicals are absorbed through the plants' vascular system,
which makes the entire plant toxic to insects. That works well for unwanted
leaf-feeding pests, but the chemicals that kill unwanted insects also go
into the nectar and pollen that pollinators need. The toxic effects to bees
can last for several months to years in pollen and nectar from just one
application. When the insecticide is applied to soil it can last for years,
adding to the imidacloprid reservoir in the plant. 

Honeybees, bumblebees and solitary bees all respond to the insecticides,
which are also commonly used for controlling emerald ash borer and Japanese
beetles. Less-than-lethal exposures can cause honeybees to have problems
flying and finding their way back to the hive, lose their sense of taste and
have more difficulty learning new tasks, according to a group of scientists
called the Xerces Society for Invertebrate Conservation, who summarized some
of the existing research on bees and neonicotinoids this year. 

Neonicotinoids are banned from use on corn and canola seed in both France
and Germany, and after two studies last spring that made a strong connection
between their use and declining bee health, support is growing in the United
States for stronger regulation both in agricultural and home use. Early this
year, beekeepers from Minnesota and California petitioned the Environmental
Protection Agency to immediately suspend sales of neonicotinoid
insecticides, but in July the EPA denied the request and said it will review
the insecticides' effects, a process that could take until 2018. More
recently, members of Congress have asked the agency to speed up the process.
Krischik says more research is needed.

Krischik and Jamison Scholer examining bees in their habitat.

CFANS-Solutions-2012-Fall-bees2

Krischik and graduate student Jamison Scholer check the status of two sets
of bees in their protected garden habitat: a control group and one fed
pesticide-laced food.

Digging in to home use

For years, beekeepers, scientists and chemical companies have argued about
the amount of insecticide used as a seed treatment. The imidacloprid seed
treatment Gaucho permits 0.675 mg AI (active ingredient) imidacloprid/seed
for corn and 0.11 mg/seed for canola, Krischik says. But the greenhouse rate
used on perennial landscape plants allows for 300 mg AI/ per 3 gallons-a 444
times higher rate on landscape plants than on field corn. Consequently,
greenhouse and urban landscapes use higher concentrations of imidacloprid,
and to make matters worse, gardeners often disregard the products'
instructions and reapply the insecticide or use it at peak flowering time,
giving home use much greater potential to affect bees and other beneficial
insects.

It gets even worse with trees, Krischik says. A surface soil application of
imidacloprid in agriculture is limited to about 4mg/sq ft. But when used to
stop emerald ash borers or Japanese beetles, the allowable application for a
similar area is 1,675 times greater. These higher application rates in urban
areas have huge implications for movement of imidacloprid into flowers and
effects on bees and beneficial insects.

Addressing the controversy

So how much imidacloprid kills a bee? Bayer says 20 parts per billion will
alter behavior and 170 ppb in food will kill a bee while it is drinking. 

So how much imidacloprid ends up in nectar and pollen from a standard
application dose in agriculture or landscapes? Is it enough to kill
pollinators?

Jamison checking bees.

Jamison checks bees in the same study kept inside a greenhouse.

The seed treatment Gaucho results in around 6 ppb imidacloprid in canola
pollen and 0.6 ppb in canola nectar, 3 ppb in corn pollen and 3 ppb in
sunflower pollen and 1.9 ppb in sunflower nectar. In landscapes, a standard
300mg dose to a 3 gallon pot results in 1,600 ppb in milkweed nectar, around
800 times more than from a sunflower seed treatment, according to Krischik.
That concentration can cause high mortality in beneficial insects other than
bees such as lady beetles or lacewings. Krischik's lab is the first to study
how the higher concentrations affect bees. 

By partnering with a local golf course that had applied a surface drench of
imidacloprid to linden trees, Krischik found that 1 month after application
the linden leaves had around 100 ppb imidacloprid-which had the desired
effect of killing Japanese beetles-but 12,865 ppb imidacloprid remained in
the soil under the linden trees. Any flowering plant growing under the
linden will pick up the imidacloprid and move it to pollen and nectar. 

"Our data demonstrates that a homeowner application to rose bushes results
in 812 ppb, which will kill any insect eating the pollen," Krischik says.
"We have seen in our trials that bees die on the flowers while feeding on a
mint treated with the standard dose or a second application of imidacloprid,
which is permitted. We showed that a rose bush will kill leaf-feeding
Japanese beetles for 3 years after one standard consumer application of
imidacloprid. However, you can apply it many times a summer."

Because the neonicotinyl insecticides (imidacloprid, thiamethoxam,
clothianidin and dinotefuran) have a similar lethal effect on bees and other
beneficial insects, the problem is enormous, Krischik says. Her lab showed
that 4 species of lady beetles, a parasitic wasp, a predatory green lacewing
and bumblebees all die at the standard application rate of imidacloprid. In
bumblebee colonies, queen mortality, colony weight and stored nectar all are
affected in direct proportion to daily dosages. Imidacloprid also reduces
bumblebee memory in her lab studies and stops bee foraging. 

Unfortunately, she says, research about neonicotinoids' effects and consumer
education on how to use them safely aren't getting the funding they need
from federal agencies. Krischik was awarded a 2009 state grant to study the
effects of imidacloprid on bees; a second grant in 2010 that would have
allowed her to investigate the uptake of ash and linden trees of
imidacloprid and potential nontarget effects on bees and beneficial insects
was awarded, but revoked six months later by state legislators who didn't
see the value in understanding consequences of the high amount of
imidacloprid used in urban landscapes. "Wow, it is frustrating," Krischik
says. 

The Xerces Society report published earlier this year also made the case for
continued long-term independent research, noting a long list of questions
about bees and neonicotinoids that no one has yet studied in depth. 

Bees are too important to be ignored, Krischik says. "If you don't support
managing them in the appropriate way, you'll lose part of your diet, a lot
of the anti-oxidants found in fruits. People rally for polar bears 3,000
miles away and that is great. We need people to rally for bees in their own
back yard."

----------

Ashley Minnerath

Pollinator Program Administrator

The Xerces Society for Invertebrate Conservation

1971 - 2011: Forty Years of Conservation!

628 NE Broadway Suite 200, Portland, OR, 97232 USA

 <mailto:ashley at xerces.org> ashley at xerces.org

Tel: (503) 232-6639, ext. 102

Toll free: 1-855-232-6639, ext. 102

Fax: (503) 233-6794

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The Xerces Society for Invertebrate Conservation is an international
nonprofit organization that protects wildlife through the conservation of
invertebrates and their habitat. To join the Society, make a contribution,
or read about our work, please visit  <http://www.xerces.org/>
www.xerces.org/

Buy our Best Selling Book:

<http://www.xerces.org/announcing-the-publication-of-attracting-native-polli
nators/> Attracting Native Pollinators. Protecting North America's Bees and
Butterflies

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