VIII SIMPOSIO INTERNAZIONALE ICPBR

HAZARDS OF PESTICIDES TO BEES

Bologna, 4-6 Settembre 2002

Effetti dell’imidacloprid sulle api

Toxicity of imidacloprid feedings on honeybee (Apis mellifera) colonies

Jean-Paul Faucon, Clément Aurières, Patrick Drajnudel, Magali Ribière, Anne-Claire Martel, Sarah Zeggane, Marie-Pierre Chauzat and Michel Aubert

AFSSA, Les Templiers, 105 route des Chappes, B.P. 111 – 06 902 Sophia-Antipolis Cédex, France. E-mail: mp.chauzat@afssa.fr

In Europe, weaknesses or losses of honeybee hives have been noticed for many years. Many factors influence hive population: environmental conditions including weather and pollutants, pathogens and use of bee races more or less adapted to local conditions. In France, the systemic insecticide GauchoNT is used as seed coating since 1994. Its active ingredient – imidacloprid – and its metabolites have been accused to be responsible of bee mortality. In order to test this hypothesis, colonies have been fed with various concentrations of imidacloprid in syrup during a full year and their summer development and winter survival have been followed and compared. Groups of 8 hives each were fed with: syrup alone, syrup supplemented with imidacloprid at a concentration of 0.5 ppb, or syrup supplemented with imidacloprid at a concentration of 5 ppb. A fourth negative control group was not fed.

Parameters to assess hive activity were: number of returning bees at 2 p.m., presence or absence of pollen brought back by bees, bee mortality outside entrances, colony weight, honey production, capped brood area size, hive population evaluated with the number of inter-frame occupied by adult bees. The other factors were: brood quality, presence of eggs and queen cells, pathologies such as acarapisosis, nosemosis, varroosis, american foolbrood, european foolbrood, chalkbrood, chronic bee paralysis. Multi-residual analysis were conducted in order to assess chemicals in wax. Specific analysis was conducted in honey and syrup to quantify imidacloprid.

These parameters followed the same trend in all groups. At the beginning of experiment (July), activity at hive entrance was high (ranging from 10 to 44 entering bees per minute) and then decrease to 3 to 30 bees per minute in December. Colony population increased until early August ranging from 8 to 19 occupied inter-frames and then decrease to a range of 7 to 11 inter-frames in September. An overall decrease of capped brood area size was observed from 10.5 to 79.8 dm2 at the beginning to 0.5 to 19.8 dm2 in late October. The statistical analysis did not indicate any negative influence of syrup supplementation with imidacloprid despite the use of very high dose (5 ppb). Other parameters – mortality, colony weight, pathologies including varroosis number – did not exhibit any significant difference between treatments.