Gaucho is the trade name for a systemic insecticide containing the active ingredient imidacloprid. It is produced by the chemical firm Bayer AG.
Imidacloprid is applied to the seed before sowing, or the leaf of the plant. It diffuses in the plant vascular system. Insects ingest it by sucking the plant fluids. Imidacloprid is a very toxic insecticide (very quick and effective on insects), and is highly persistent in the crop. It is widely used on sunflowers, rice, vegetables as well as on corn (maize). The basis of the toxicity is the excessive activation of nicotinic acetylcholine receptors in the insect nervous system.
Seed applied insecticides have been gaining acceptance as a preferred way to deal with numerous insects as they are easy to use, comparable in cost to most traditional insecticides used at sowing time. Some also indicate that it might be better for the environment because less chemical is required than for broadcast or banded applications, or at least because less chemical is sprayed in the air. It is also easier and safer to use for the farmer. However, some note that the use of seed-applied insecticides at each season implies the chemical is used whether there is need to fight insect or not.
Gaucho use is highly controversial in France, where its use is believed to be linked to high losses in bees. According to the National Union of French Beekeepers, the number of hives in France has plummeted to one million in 2003, from 1.45 million in 1996. Between 1995 and 2001, the average production of honey went from 75 kg/hive down to 30 kg/hive. The AFFSA indicate the national production went down from 40000 tons to 25000 per year.
French beekeepers claim that Gaucho, as a seed treatment for sunflowers has killed many bees and caused a significant drop in honey production.
Some requested that systemic insecticides uses be withdrawn from crops where bees might be affected, while others called for a complete ban on Gaucho use.
In France, Gaucho started being used in 1994 as a seed-coating for sunflowers. The following years, some beekeepers mentionned the possibility of a relationship between the pesticide and some behavioral troubles in bees. Bayer CropScience made some studies on the topic, which concluded Gaucho was a non toxic to bees. At this point, most discussions were kept rather private between Bayer and beekeeper associations.
However, during summer 1997, heavy losses of bees where observed in several regions of France and the controverse became public.
In 1998, a french official study was conducted, which goal was to determine whether Gaucho was responsible for the population decrease, as well as the reduction in honey production during the flowering season of sunflowers.
Ecotoxicology studies had to define the living being in danger (the bees, to define the chemical concerned (imidaclopride) to evaluate the quantity necessary to kill the living being with the chemical and define the concentrations at which there is no detrimental effects on the living being
In the case of the accusation carried out against imidaclopride, the issue is not the direct death of the bees, but behavioral changes (disorientation, feeding issues, communication disturbance). Initial studies were aimed at determining the minimal amount for which bees showed these behavioral changes.
The study, lead by AFSSA (Association de Coordination Technique Agricole et Centre National d'Etudes Vétérinaires et Alimentaires), in four different areas showed no differences in terms of bees behavior, mortality, evolution of the beehives and honey harvest with or without Gaucho.
A study led by Wilhelm Drescher in 1998 from the University of Bonn, on the activity of bees in sunflower fields in western france, concluded that no results could prove Gaucho, used on sunflower seeds, had a detrimental effect on bees. It also mentionned that other possibilities, such a viral diseases favored by varroa larvae (population of such being on the rise since 1996 due to appearance of resistance to acaricides). It essentially concluded that the French bee loss was not linked to imidacloprid but to a viral disease or a spiroplasm in bees which produces similar symptoms.
In parallel several studies have been conducted by Bayer CropScience to evaluate the risk for bees, related to the use of Gaucho on sunflowers.
Bayer claimed that several studies had been made in open air as well as in greenhouse in Argentina, Canada, Germany, France, Great Brittain, Italy, Sweden, South Africa, Hungary and USA, and that all those studies confirmed Gaucho was not dangerous to bees.
Bayer also claimed that other arguments may be provided to explain the loss of bees. They indicated that in a study led in 1975 (Wilson, Menapace), bees decline had been obverved in 27 american states. Most disappearances were seen in wet and fresh spring. Inspectors mentionned a disease, famines, unusually wet and fresh weather, diarhea, lack of pollen, dead queens, genetic defaults, stress...
Another study by Kulincevic et al in 1983, mentionned that the primary reason for malnutrition in bees, is an insufficient pollen offer. It was mentionned modern techniques could help by offering food substitutes to bees, but that poor substitutes (such as soja) could provoke bees decline.
Jean Glavany renewed the ban in 2001 for two additional years and asked a panel of experts to make an complete epidemiological study to try to figure out all the factors that might explain bees decline, still observed during these years.
At the end of 1998, studies indicated there were no effects, but doses were very little and non measurable in laboratory. A second set of studies was lauched in 1999, to define :
The "Commission des Toxiques" brought these conclusions in 2001 :
Gerard Eyries, marketing manager for Bayer's agricultural division in France was cited saying studies confirmed that Gaucho left a small residue in nectar and pollen, but there was 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 studies indicated that concentrations were especially high when the plant is young. These would often be of
In 2001, Bayer also brought a judicial case against Maurice Mary, one of the leaders of the French association of beekeepers for disparagement of the chemical Gaucho. The action was dismissed by the judge in May 2003.
In 2003, agricultural Minister Jean Glavany extended again the suspension on the use of Gaucho on sunflower seeds.
In spite of a 4 years ban already on sunflower seeds treatment, a significant drop in bee individuals is still observed. Beekeepers were cited as saying the measure was insufficient, as studies found that Gaucho left a residue which meant that even after two years, plants sowed on the same spot as the crop originally treated contained traces of the product.
Some also suggest that the bee colony losses could also be due to the use of imidacloprid on corn as well, or by the replacement of it by another systemic insecticide called Fipronil. 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 accute toxicity by Fipronil (as the active chemical in the systemic insecticide called Regent), while it was recognised Gaucho had no responsability in the bees death. Some national field studies are currently under way (2003) to assert the responsability of Gaucho.
A similar battle is occurring in Nova Scotia, where beekeepers are accusing Gaucho used on potatoes for massive losses of bees needed for blueberry pollination.Gaucho, a seed applied insecticide
Gaucho controversy
Initial observations of bees decline
1998 : estimation of Gaucho toxicity
Gaucho banned as a sunflower seed treatement in 1999
Finally, Jean Glavany, minister of Agriculture in the French government used the precautionary principle and decided to withdraw the use of imidacloprid as a sunflower seed treatment in 1999. Bayer scientists denied again that the product was responsible for the colonies death in a meeting in 2000.Second set of studies in 1999 and 2000
Bayer CropScience results show that the maximal dose for which no effect was observed was 20 ppb, while the amount of residue in parts of the plant available to the insect (aerial parts) was below 1.5 ppb. They concluded bees could not be in contact with high enough concentrations to be able to be affected by the pesticides, and that the sunflower seed treatment was risk free for bees.
The commission concluded that it had no serious indicators suggesting Gaucho might be dangerous to bees. However, the commission suggested a risk could exist with seed-treated corn pollen.
Bayer then agreed that the insecticide may cause disorientation of bees at levels above 20 parts per billion of the active ingredient. Recent studies by researchers at the Institut National de la Recherche Agronomique (INRA) suggest that bee behaviour is affected at levels between 3-16 ppb or possibly even 0.5 ppb.
Current situation of bees decline