Author Topic: Neonicotinoid pesticides tied to collapse of bee colonies  (Read 1235 times)

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Neonicotinoid pesticides tied to collapse of bee colonies
« Reply #1 on: March 29, 2012, 06:18:12 AM »
By Miguel Llanos, msnbc.com

A widely used crop pesticide first introduced in the 1990s has caused significant changes to bee colonies worldwide and removing it could be the key factor in restoring nature's army of pollinators, according to two studies released Thursday.

A bee with a transmitter glued to its back was one of the specimens in a study that used the radio technology to track what happened to bee colonies exposed to a widely used pesticide.

The scientists behind the studies called for regulators to consider banning the class of chemicals known as neonicotinoid insecticides. In the U.S., the Environmental Protection Agency told msnbc.com that the studies would be incorporated into a review that's currently underway.A pesticide trade group immediately questioned the data, saying the levels of pesticide used were unrealistic, while the researchers said the levels used were typical of what bees would find on farms.

"Our study raises important issues regarding pesticide authorization procedures," stated Mikael Henry, co-author of a study on honey bees. "So far, they mostly require manufacturers to ensure that doses encountered on the field do not kill bees, but they basically ignore the consequences of doses that do not kill them but may cause behavioral difficulties."

"There is an urgent need to develop alternatives to the widespread use of neonicotinoid pesticides on flowering crops wherever possible," added the authors of the second study on bumble bees.

Last week, a coalition of environmental groups and beekeepers asked the EPA to suspend the pesticide's use.
The studies are the first to go outside the lab and into the fields, where the experts said they detected how the pesticide impacts bees as they collect pollen and pollinate flowers and crops.

Honey bee populations have been crashing around the world in recent years, and pesticides have been suspected, along with other potential factors such as parasites, disease and habitat loss, in what's known as Colony Collapse Disorder. In the U.S., some beekeepers in 2006 began reporting losses of 30-90 percent of their hives, according to the U.S. Department of Agriculture.

Combating Colony Collapse Disorder is hardly an esoteric exercise. The USDA notes that "bee pollination is responsible for $15 billion in added crop value, particularly for specialty crops such as almonds and other nuts, berries, fruits, and vegetables.

"About one mouthful in three in the diet directly or indirectly benefits from honey bee pollination," it adds.
Published in the peer-reviewed journal Science, one study by British scientists looked at honey bees and the other by French scientists examined bumble bees, which unlike honey bees live in the wild but also are key pollinators.
In the bumble bee study, researchers concluded that colonies treated with nonlethal levels of the pesticide "had a significantly reduced growth rate and suffered an 85% reduction in production of new queens" compared to colonies without the pesticide.
"It was quite massive," researcher Penelope Whitehorn said of the reduction at a press conference Thursday. (Click here for audio of the news conference.)
"Bumble bees have an annual life cycle and it is only new queens that survive the winter to found colonies in the spring," the authors noted. "Our results suggest that trace levels of neonicotinoid pesticides can have strong negative consequence for queen production by bumble bee colonies under realistic field conditions, and this is likely to have a substantial population-level impact."

In the honey bee study, radio transmitters were attached to the back of bees to see how they foraged in conditions with and without the pesticide.
The pesticide, the researchers concluded, impaired the homing ability of bees and exposed bees were two to three times more likely to die while away from the hive. That "high mortality ... could put a colony at risk of collapse" within a few weeks of exposure, especially in combination with other stressors, they noted.
"We were actually quite surprised by the magnitude," Henry told reporters.
CropLife America, a pesticides trade group, said in a statement to msnbc.com that the studies "fail to account for the many real-world factors that impact bee and colony health, and the researchers used unrealistic pesticide dose levels that are not commonly found in practical field situations in agriculture."
The EPA, contacted by msnbc.com, provided a statement saying that it has "begun reviewing the two studies ... and they will be considered as part of registration review." Non-EPA scientists will weigh in at a special meeting in the fall, it added.
The prevailing view among most scientists and regulators is that "complex interactions among multiple stressors" are to blame, the EPA stated.  "While our understanding of the potential role of pesticides in pollinator health declines is still progressing, we continue to seek to learn what regulatory changes, if any, may be effective."


Pesticide Toxicity Profile: Neonicotinoid Pesticides1
Frederick M. Fishel2

This document provides a general overview of human toxicity, provides a listing of laboratory animal and wildlife toxicities and a cross reference of chemical, common and trade names of many neonicotinoid pesticides registered for use in Florida.

General
The mode of action of neonicotinoid pesticides is modeled after the natural insecticide, nicotine. They act on the central nervous system of insects. Their action causes excitation of the nerves and eventual paralysis which leads to death. Because they bind at a specific site (the postsynaptic nicotinic acetylcholine receptor), they are not cross-resistant to the carbamate, organophosphate, or synthetic pyrethroid insecticides, which was an impetus for their development. As a group, they are effective against sucking insects, but also chewing insects such as beetles and some Lepidoptera, particularly cutworms. All neonicotinoid products are classified as general use and have been registered under EPA's Conventional Reduced Risk Program due to their favorable toxicological profiles.

Acetamiprid is for use against sucking insects, such as aphids and whiteflies, on leafy vegetables, cole crops, citrus, cotton, ornamentals, and fruiting vegetables. Ready-to-use formulations are available in addition to wettable powders and water-dispersible granules.

Clothianidin was registered in 2003 by Bayer initially for corn and canola seed treatment use. Additional approved sites include grapes, pome fruit, rice, tobacco, and turf and ornamentals.

Imidacloprid was first registered for use in the U.S. in 1992 and is possibly the most widely used insecticide of the group. It has a wide range of target pests and sites, including soil, seed, structural, pets, and foliar treatments in cotton, rice, cereals, peanuts, potatoes, vegetables, pome fruits, pecans, and turf. It is a systemic with long residual activity and particularly effective against sucking insects, soil insects, whiteflies, termites, turf insects, and Colorado potato beetle. Products are available in dusts, granules, seed dressings as flowable slurry concentrates, soluble concentrates, suspension concentrates, and wettable powders. The application rates for neonicotinoid insecticides are much lower than older, traditionally used insecticides.

Thiamethoxam's chemical structure is slightly different than the other neonicotinoid insecticides, making it the most water soluble of this family. Because of its greater water solubility, it moves readily in plant tissue. Products are labeled for soil, seed, and foliar treatments to a wide range of vegetable and field crops. Product formulations include emulsifiable concentrates, water dispersible granules, and soluble concentrates.

Toxicity
Neonicotinoids are classified by the EPA as both toxicity class II and class III agents and are labeled with the signal word “Warning” or “Caution.” Because the neonicotinoids block a specific neuron pathway that is more abundant in insects than warm-blooded animals, these insecticides are more selectively toxic to insects than mammals. The most available toxicity data of the neonicotinoids is with imidacloprid. These data indicate that it is less toxic when absorbed by the skin or when inhaled compared to ingestion. It causes minor eye reddening, but is non-irritating to the skin. Signs of toxicity in rats include lethargy, respiratory disturbances, decreased movement, staggering gait, occasional trembling, and spasms. There are no accounts of human poisoning, but signs and symptoms of poisoning would be expected to be those similar for rats. A chronic toxicity study showed that rats fed up to 1,800 ppm resulted in a No Observable Effect Level (NOEL) of 100 ppm. The EPA categorizes imidacloprid as a “Group E” (no evidence of carcinogenicity). In animals and humans, imidacloprid is quickly and almost completely absorbed from the gastrointestinal tract, and eliminated via urine and feces within 48 hours. Of the neonicotinoids, imidacloprid is the most toxic to birds and fish. Both imidacloprid and thiamethoxam are highly toxic to honeybees. Mammalian toxicities for neonicotinoid pesticides registered in Florida are shown in Table 1. Table 2 lists the toxicities to wildlife by the common name of the neonicotinoid pesticide. Table 3 provides a cross listing of many of the trade names that these products are registered and sold by in Florida.

Bee Keeping Resources at Back 40 Books:

Table 3. Cross reference list of common, trade and chemical names of neonicotinoid insecticides.
Common name*   Trade names**     Chemical Name
 
Acetamiprid
 Acetamiprid®, Assail®, Tristar®
 (E)-N-(6-chloro-3-pyridinyl)methyl)-N1-cyano-N-methylacetamidine
 
Clothianidin  Acceleron®, Arena®, Belay®, Celero®, Clutch®, Nipsit Inside®, Poncho®  (E)-1-(2-chloro-1,3-thiazol-5ylmethyl)-3-nitroguanidine
 
Imidacloprid
 Admire®, Advantage®, Gaucho®, Merit®, Premise®, Touchstone®
 1-(6-chloro-3-pyridin-3-ylmethyl-N-nitroimidazolidin-2-ylidenamine
 
Thiamethoxam
 Cruiser®, Platinum®
 3-(2-chloro-1,3-thiazol-5-ylmethyl)-1,3,5-oxadiazinan-4-ylidenene(nitro)amine
 
*Basic molecule; isomers not listed.
 
**Does not include manufacturers' prepackaged mixtures; major agricultural brands for basic manufacturers.
 
Insect Pest Management Department at Back 40 Books:url=http://www.back40books.com/get_list_1149.htm][/url]