Imidacloprid effects on bees

Imidacloprid is a systemic neonicotinoid insecticide produced by the German chemical firm Bayer CropScience and sold under such trade names as Gaucho, Admire, Merit, Advantage, Confidor, Provado, and Winner. It acts as an insect neurotoxin and works by interfering with the transmission of nerve impulses in insects by binding to specific nicotinic acetylcholine receptors. Imidacloprid has been suspected of being associated with honeybee colony collapse disorder in man made hives. It has not however been directly linked to this disorder and research in recent years now points at other causes such as miticide sprays used by bee keepers to control mite parasites that are directly sprayed on the hive, a virus, and a fly known to parasitize American bumble bees and wasps has recently been discovered parasitizing California honey bees, causing bees to abandon their colonies in the night. Bees parasitized by the phorid fly became disoriented, "turning into zombies", flying out into the night to die the next day. Parasitism was widespread in the study area near the San Francisco Bay. Parasitism was found at 77% of the sites they investigated. The highest rate of parasitism was 91% of the nocturnally active bees at one site.

As a systemic pesticide, imidacloprid translocates or moves readily from the soil into the leaves, flowers, fruiting bodies, pollen, nectar, and guttation fluid of plants. Imidacloprid has limited mobility in the soil and does not bioaccumulate. For imidacloprid to be ingested in bees, it has to be translocated into plants and then the flowers where the bees can ingest it as they forage for pollen. Imidacloprid and other pesticides have been shown to weaken bees, making them more susceptible to parasites and other health issues. However, scientists no longer point directly at imidacloprid as the cause of this disorder. In fact despite banning imidacloprid and other neonicotonoids in France in 1999, Bee colony collapse disorder continues to be a serious issue. In Australia, where imidacloprid is widely used, there are no reports of colony collapse disorder, and there are also none of the viruses and mites that have also been linked as possible causes.

Contents 1 History 2 Toxicity of imidacloprid to bees 2.1 Acute 2.2 Sublethal 2.3 Chronic 3 Synergistic effects 4 Other studies 5 Uncertainties 6 Events in the decline of bees 6.1 2001 6.2 2002 6.3 2003 6.4 2008 6.5 2010 6.6 2011 7 Media portrayal 8 See also 9 References 10 External links

History

Over the past 20 years there has been much conjecture and guessing at the cause of bee die off in man made hives. And while imidacloprid has been pointed at by some, it must be recognized that research now points at other causes and that this epidemic was not happening everywhere imidacloprid was being used, but spread much like a disease spreads. Even in France, despite the widespread use of Imidacloprid, not all hives in all areas experienced die off at the same time. While a serious issue in some places in the 1990's, it did not become recognized to be a serious issue in the United States until the mid 2000's.

Imidacloprid was first registered in the United Kingdom in 1993 and in the United States and France in 1994.^[1] In the mid to late 1990s, French beekeepers began to experience die-offs of bees in their man made hives, and blamed the introduction of imidacloprid to fields that had been recently used. In 1999 the French Minister of Agriculture suspended the use of imidacloprid on sunflower seeds. The French Agriculture Minister also appointed a team of expert scientists to examine the impact of imidacloprid on bees. In 2003, this team of experts called the Comite Scientific et Technique issued a 108-page report, which concluded that imidacloprid poses a significant risk to bees.^[2] In 2004, the French Minister of Agriculture suspended the use of imidacloprid as a seed treatment for maize (corn).

Toxicity of imidacloprid to bees

Acute

On an acute basis, the lethal dose to kill 50% of the population of adult honeybees (LD50) equals 0.078 micrograms active ingredient/bee (ug a.i./bee) for contact toxicity and 0.0038 ug a.i./bee for oral ingestion.  Other insecticides that are as toxic or more toxic than imidacloprid include spinosad, emamectin benzoate, clothianidin, fipronil, thiamethoxam, and dinotefuran.[3]

Sublethal

The majority of studies that measure toxicity of pesticides to bees focus on estimating the lethal dose (LD50) in acute toxicity tests to adult honeybees. This is only a partial measure of the harmful effects that pesticides can have on bees. For a complete analysis of the impact of pesticides to bees, sublethal effects should be considered.

Dozens of research articles have been published in peer-reviewed journals, which show sublethal effects to adult bees exposed to low levels of imidacloprid. In these studies, sub-lethal doses of 1-24 ug/kg and 0.1 - 20 ng/bee have been shown to impair navigation, foraging behavior, feeding behavior, and olfactory learning performance in honeybees (Apis mellifera).^{[4][5][6][7][8][9][10]} Other studies examining higher levels of imidacloprid (50 - 500 ppb) also found that imidacloprid decreases foraging activity and affects bee mobility and communication capacity.^[11][12][13]

Chronic

In 10-day chronic feeding studies with honeybees (Apis mellifera), 50% mortality was reached at levels between 0.1 and 10 ug/kg imidacloprid.^[14] Other chronic toxicity studies conducted by Moncharmont et al. (2003) and Decourtye et al. (1999) have demonstrated chronic NOAEC values of <4 ppb and 4 ppb, respectively in honeybees.^[15][16] In bumble bees, Mommaerts et al. (2009) demonstrated a LOAEC of 10 ppb for imidacloprid.^[17]

Many tunnel and field studies have been conducted to show the potential effects of imidacloprid in the natural environment. Unfortunately, most of these field studies have design and implementation deficiencies, which make them difficult to use.^[18][19]

Synergistic effects

Two research teams led by Jeff Pettis at the U.S. Department of Agriculture and Cedric Alaux at INRA/France have demonstrated that interactions between the pathogen Nosema and a neonicotinoid imidacloprid significantly weaken the immune systems of honeybees (Apis mellifera). In their research, Alaux et al. (2010) found that bees infected with Nosema and exposed to 0.7 ug/kg imidacloprid had an increased rate of mortality compared to the controls. The combination of Nosema and imidacloprid also significantly decreased the activity of glucose oxidase, an important enzyme that allows the bees to sterilize their colony and brood food. Without this enzyme, bees can become more susceptible to infections by pathogens. Both the USDA study and the INRA study demonstrate that a combination of stressors (pesticides and pathogens) may be responsible for the recent high level of bee losses.^[20][21]

In 2012, researchers announced findings that sublethal exposure to imidacloprid rendered honey bees significantly more susceptible to infection by the fungus Nosema, thereby suggesting a potential link to CCD, given that Nosema is increasingly considered to contribute to CCD.^[22]

Other studies

Bayer CropScience studies show that the maximum dose of imidacloprid for which no adverse effects were observed in bees is 20 ppb. Since Bayer claims that residue levels are usually below 5 ppb in pollen and nectar, they contend that imidacloprid poses a negligible risk to bees.

Gerard Eyries, marketing manager for Bayer's agricultural division in France, states that studies confirm that imidacloprid leaves a small residue in nectar and pollen, but there is no evidence of a link with the drop in France's bee population, adding, "It is impossible to have zero residue. What is important is to know whether the very tiny quantities which have been found have a negative effect on bees." He also added that the product was sold in 70 countries with no reported side effects.

Other independent studies have indicated that imidacloprid residues in plants can be higher:^[23][24][25]

• 10 to 20 ppb in upper leaves
• 100 to 200 ppb in other leaves
• 1.5 ppb in nectar
• 2 to > 13 ppb in pollen

Uncertainties

It is important to note that the majority of studies conducted on pollinators have been performed in adult honeybees (Apis mellifera). Very few studies have been conducted on wild bees, most of which are solitary and raise their young in burrows and small colonies. There are also few studies that have been conducted on brood, larvae, or the queen, making it difficult to determine the impact of pesticides on different members of the colony and life stages of the bee.

Events in the decline of bees

2001

In 2001, Bayer CropScience brought a judicial case against Maurice Mary, one of the leaders of the French Association of Beekeepers for disparagement of the chemical imidacloprid. The action was dismissed by the court in May 2003.

2002

A similar battle occurred in Nova Scotia, where beekeepers believed that imidacloprid used on potatoes resulted in massive losses of bees, which are needed for blueberry pollination.

2003

In 2003, French Agricultural Minister Jean Glavany again extended the suspension of the use of imidacloprid on sunflower seeds. In spite of a four-year ban already on sunflower seeds treatment, a significant drop in bee individuals was not observed. Beekeepers were cited as saying the measure was insufficient since studies found that imidacloprid accumulates in soil and leaves a residue. Even after two years, plants sowed on the same spot as the crop could contain traces of the product.

Some also pointed out that bee colony losses could also be due to the use of imidacloprid on other crops such as corn, or from the replacement of imidacloprid by another systemic insecticide called fipronil. Fipronil is as toxic to honeybees on an acute oral basis as imidacloprid. Indeed in May 2003, the DGAL (Direction Générale de l'Alimentation du ministère de l'Agriculture ) indicated death of bees observed in the south of the country had been caused by acute toxicity by fipronil (trade name Regent). Imidacloprid was not believed to be the likely cause for the bees death.

2008

In June 2008, the German Federal Office of Consumer Protection and Food Safety suspended the registration of eight neonicotinoid pesticide seed treatment products used in oilseed rape and sweetcorn, a few weeks after honeybee keepers in the southern state of Baden Württemberg reported a wave of honeybee deaths linked to one of the pesticides, clothianidin.^[26]

In August 2008, the Coalition against Bayer Dangers (CBG) brought a legal case against Werner Wenning, Bayer's chairman, for marketing dangerous pesticides (neonicotinoids), which are causing the death of bees worldwide.^[27]

2010

In November 2010, an EPA document was released, detailing the risks to honeybees from exposure to clothianidin, a neonicotinoid similar to imidacloprid. The EPA document states: "This compound is toxic to honey bees. The persistence of residues and potential residual toxicity of clothianidin in nectar and pollen suggests the possibility of chronic toxic risk to honey bee larvae and the eventual instability of the hive."^[28]

2011

In January 2011, an online petition to save the bees was launched by Avaaz.org to push the United States and European Union to join the ban of the neonicotinoid pesticides.^[29]

Media portrayal

In October 2009, a documentary film, Vanishing of the Bees, was released in theatres in the UK. The film interviewed a number of experts in connection with CCD and suggested a link does exist between neonicotinoid pesticides and CCD. However, the experts interviewed conceded no firm scientific data yet exist. Industry-sponsored studies appear to be inconsistent with those produced by independent scientists.^[30][31]

In February 2010, the documentary film Nicotine Bees was released. This film analyzes the possible factors contributing to the large bee die-offs worldwide and concludes that the large use of neonicotinoids is the most probable cause of the recent bee die-offs.^[32]

See also

• Pesticide toxicity to bees
• Bees and toxic chemicals
• Colony collapse disorder
• Vanishing of the Bees

References

External links

• webpage from Bayer CropScience page on Imidacloprid and Bee safety noting independent trials show product as safe for bees
• link to example of Bayer product containing Imidiacloprid noting product is a high risk to bees
• juridical case lost by Bayer, requalified defaming toward Maurice Mary
• demonstration against Imidacloprid and links on beekeeping.com
• imidacloprid and "mad bee disease"
• Honey bees in US facing extinction, The Telegraph, 14 March 2007
• Various links on scientific reports and news articles (French & English) on the website of the Union Nationale de l'Apiculture Française (UNAF) union
• British Bee Keepers Association position on Bayer's pesticides
• Official documentary website of the 2009 documentary film Vanishing of the Bees
• Bayer-kills-bees.com advocacy site updated about five times per month
• How to Reduce Bee Poisoning from Pesticides PNW 591, (Pacific Northwest Extension)