We used LC/MS-MS to analyze samples of honey bees, pollen stored in the hive and several potential exposure routes associated with plantings of neonicotinoid treated maize. Our results demonstrate that bees are exposed to these compounds and several other agricultural pesticides in several ways throughout the foraging period. During spring, extremely high levels of clothianidin and thiamethoxam were found in planter exhaust material produced during the planting of treated maize seed. We also found neonicotinoids in the soil of each field we sampled, including unplanted fields. Plants visited by foraging bees (dandelions) growing near these fields were found to contain neonicotinoids as well. This indicates deposition of neonicotinoids on the flowers, uptake by the root system, or both. Dead bees collected near hive entrances during the spring sampling period were found to contain clothianidin as well, although whether exposure was oral (consuming pollen) or by contact (soil/planter dust) is unclear. We also detected the insecticide clothianidin in pollen collected by bees and stored in the hive. When maize plants in our field reached anthesis, maize pollen from treated seed was found to contain clothianidin and other pesticides; and honey bees in our study readily collected maize pollen. These findings clarify some of the mechanisms by which honey bees may be exposed to agricultural pesticides throughout the growing season. These results have implications for a wide range of largescale annual cropping systems that utilize neonicotinoid seed treatments.
Source:
Krupke CH, Hunt GJ, Eitzer BD, Andino G, Given K (2012) Multiple Routes of Pesticide Exposure for Honey Bees Living Near Agricultural Fields. PLoSONE 7(1): e29268. doi:10.1371/journal.pone.0029268 (attached)
Honeybees are sensitive to seed treatments used in virtually all corn and many other seeds. There seem to be multiple modes of exposure for bees, but it's been found that talc, used to lubricate treated seeds in planters, harbors these neonicotinoid insecticides at levels 700 times the lethal level for honeybees, and is being carried in the air during seed planting and landing on flowering plants where honeybees can be exposed to them.
Reports of large numbers of dead bees just outside their hives at multiple apiaries in Indiana, April 2010, prompted a Purdue University study to investigate what was causing the honeybee deaths.
Integrated Pest Management (IPM) specialist and entomologist at Purdue, Christian Krupke, began looking at what was being applied to fields at the same time-planting season-as the bee deaths were being reported.
"I went through the laundry list of things that were going on corn and soybean fields," Krupke shared. Herbicides are primarily what are being used during planting, but there are also insecticides and fungicides used on seed.
He said when they visited the affected apiaries, they saw bees exhibiting classic neurotoxic symptoms-nerve poisoning.
"Most of our insecticides we use are nerve toxins," he noted. Evaluating the dead bees they found neonicotinoid insecticides (insecticides that affect the central nervous system of insects), particularly thiamethoxam and clothianidin, better known as Cruiser and Poncho, at lethal levels in the dead honeybees. Seed treatments of field crops, primarily corn, are the only major source of these two compounds-there aren't really homeowner applications of these compounds, Krupke said. Virtually all corn seed is treated with Cruiser and Poncho, as well as most soybeans, canola, sorghum, cotton, wheat and other seeds.
The underlying question in the study was figuring out how the honeybees were ingesting the seed-applied insecticides. The study found pollen stored in the hives with dead bees had high levels of neonicotinoid insecticides, so the bees were getting contaminated pollen somewhere and bringing it back to the hive.
"So bees were going somewhere where [treated seed] was being planted," he said, "but how does it get from being on the seed and planted in the ground to being somewhere where bees can get it. Bees are interested in flowers-pollen and nectar. They're not interested in unplanted corn fields. They're not interested in bare soil."
The study looked at the paths the neonicotinoid insecticides could possibly take to getting into pollen. They started with soil. Planting happens in spring when soil becomes dry enough to be workable, so it's dusty and windy. "The dust from where soil is stirred up clearly can move a long ways," Krupke noted. They sampled topsoil and subsoil in fields with known histories and found neonicotinoid insecticides two-plus years after treated seed was planted in the soil. The half life of Poncho and Cruiser is about three years, so it hangs around for a long time.
The next place they looked was dandelions, as they're the most readily available source of pollen for bees in the spring during planting season. And a lot of dandelions grow near fields. Neonicotinoid insecticides were found on the dandelion heads, although not at levels that would explain the high mortality seen in affected hives, Krupke said.
The next area of examination was talc, which is widely used to lubricate treated seeds in the planter to avoid skipping and seed doubling caused by seeds sticking together from the insecticide treatment. "When you have a vacuum planter, you have a system of fans and manifolds, but you also have an exhaust fan," he pointed out. "Coming out of the exhaust fan is a lot of talc."
Some talc exits with the seed, some exits in the planter exhaust and about 30 percent stays in the manifold system until it's cleaned out, with no cautionary notes or directions in manuals about how or where to safely dispose of the contaminated talc. About 5 million pounds of talc are used annually for planting corn seed alone.
Sampling the used talc they found as much as 50 million parts per billion (ppb) of the neonicotinoid insecticides-700 times the lethal level for bees. Whatever is on the seed comes off in the talc. Talc particles are very small and potentially very mobile, meaning they can easily land on flowering plants near fields, exposing honeybees.
Another issue the research noted is neonicotinoid insecticides are persistent and systemic. They get taken up by the seed as it grows-protecting the seed and seedling. When the crop starts to shed pollen the neonicotinoid insecticides are found in the pollen as well, although in low levels. While the levels in the pollen were low, they found that apiaries located near corn fields had 44.5 percent of their pollen collected from corn.
"We were surprised at the volume of pollen from corn the bees collected," Krupke noted. Bees will only travel as far as they need to get pollen.
Krupke acknowledged that although the study showed unintended negative consequences from seed-applied insecticides, the seed treatments are important, but possibly not at the broad level they're currently used.
"We're using [neonicotinoid insecticides] everywhere. In IPM we don't like to see blanketing-every crop treated, especially 85 million acres of corn-with the same pesticide application and level of application."
Honeybees living near agricultural fields have multiple routes of exposure to neonicotinoid insecticides-dandelions, soil, talc and pollen.
FROM AGRI-VIEW MAGAZINE, BY SHANNON HAYES, MANAGING EDITOR
http://www.agriview.com/news/crop/seed-treatments-linked-to-honeybee-de…
Posted: Thursday, February 2, 2012
Dr. Krupke Discusses His Research On Bees And Neonicotinoids
The Organic View Radio Show, March 2, 2012
http://www.blogtalkradio.com/theorganicview/2012/03/02/dr-krupke-discus…
An EPA memo dated September 28, 2005 (attached) summarizes the Environmental Fate and Effects Division’s (EFED) screening-level Environmental Risk Assessment for Clothianidin:
- Clothianidin is expected to dissipate very slowly under terrestrial field conditions, based on the results of five bare ground field experiments conducted in the US and Canada. Half-lives of clothianidin, based on residues in the 0-15 cm soil depth, were 277 days (Wisconsin sand soil, incorporated), 315 days (Ohio silt loam soil, not incorporated), 365 days (Ontario silt loam soil, incorporated), and 1,386 days (North Dakota clay loam soil, not incorporated), and could not be determined at a fifth site due to limited dissipation during the 25-month study (Saskatchewan silty clay loam soil, incorporated). Incorporation did not appear to be a significant factor in determining the rate of dissipation. Clothianidin was generally not detected below the 45 cm soil depth except at one site, where it moved into the 45-60 cm depth. No degradates were detected at >10% of the applied, and degradates were generally only detected in the 0-15 cm soil layer. However, in many cases most of the parent remained untransformed at the close of the study; further accumulation of degradates could have occurred. Two studies were conducted to investigate leaching of clothianidin under field conditions. These studies were conducted in the Federal Republic of Germany and were apparently designed to fulfill certain European regulatory requirements. In these monolith lysimeter studies, 42 to 59% of the applied remained in the soil approximately 3 to 4 years following the first of two applications, and residues were primarily undegraded clothianidin.
- Direct contact and dietary exposure studies of honeybees indicate that clothianidin is highly toxic to honeybees (acute contact LD50 = 0.0439 µg/bee and acute oral LD50 = 0.0037 µg/bee). There is the potential for toxic exposure to honeybees, as well as other nontarget pollinators, through the translocation of clothianidin residues in nectar and pollen. In addition, studies indicate that clothianidin residues may affect foraging behavior. Data from studies determining the toxicity of residues on foliage indicate that clothianidin should not be applied to blooming, pollinating or nectar producing parts of plants because clothianidin will remain toxic to bees for days after a spray application. In honey bees, the effects of this toxic exposure may include lethal and/or sub-lethal effects in the larvae and reproductive effects to the queen. The field study EFED is requesting should resolve uncertainties dealing with clothianidin’s affects on bees. Clothianidin’s major risk concern is to nontarget insects (that is, honey bees). EFED expects adverse effects to bees if clothianidin is allowed to be sprayed on blooming, pollen-shedding, or nectar producing parts of plants. Although EFED does not conduct a risk quotient based risk assessment on non target insects, information from standard tests and field studies, as well as incident reports involving other neonicotinoids insecticides (e.g., imidacloprid) also suggest the potential for long term toxic risk to honey bees and other beneficial insects. Further studies may be needed to determine toxicity to honeybees from granular, seed treatment or foliar spray applications.
- The available data on clothianidin shows that the compound is relatively persistent to very persistent under most circumstances. Clothianidin is stable to hydrolysis at all pH's at environmental temperatures, moderately to highly stable under aerobic soil metabolism conditions (half lives range from 148 to 6,900 days).....Certain degradates appeared to accumulate in some soils under some conditions; over the very long term significant contamination of soil and water with these products might occur. The terrestrial field dissipation studies confirm the findings in the laboratory studies. Clothianidin was found to be persistent in the field (half lives of 277 days, 1,400 days, and too high to calculate).
- The Agency acknowledges that pesticides have the potential to exert indirect effects upon the listed organisms by, for example, perturbing forage or prey availability, altering the extent of nesting habitat, and creating gaps in the food chain
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