| |
|
 |
> ARCHIVIO EVENTI INA | |||||||||||||||||||||||||||
VIII SIMPOSIO INTERNAZIONALE ICPBR HAZARDS
OF PESTICIDES TO BEES Effetti dell’imidacloprid sulle api Long-term
toxicity assessment of imidacloprid (Gaucho®) to evaluate side effects
on honey bees exposed to treated sunflowers in Argentina A long-term field trial (226 days) was conducted to assess the effect of imidacloprid on population development and honey production of beehives exposed to sunflowers which had been seed-treated with Gaucho®. The trial was conducted in two parcels of 24 ha each, sown with 60.000 seeds/ha of sunflower, commercial hybrid (DEKASOL 3915 G3). The seeds of the test parcel were treated with 0,24 mg imidacloprid (a.i.) per seed and the seeds sown in the control parcel were left untreated. Apis mellifera (variety Italian) populations and sister queens of the same age were placed in 16 hives, consisting of two hive bodies and an excluder each. At the beginning of the study, the shape and population structure of the hives was uniform. Beehives were placed at the center of each parcel when sunflower came into bloom, and remained there during the flowering period, according to general pollination practices. After bloom, the beehives were transferred to a natural pasture field and their development was assessed during the subsequent 216 days. The control of bee parasites and diseases was done according to the usual beekeeping practice in Argentina, and the sanitary status of the hives as well as the whole study, were audited by personnel of the National Service of Health and Quality of Agricultural Products (SENASA). The evolution of the hives was assessed by analyzing population parameters sensitive to factors affecting the development of the hives: beehive weight, nectar, pollen, brood and honey production, foraging activity, pollen entrance and mortality. Residue analysis (HPLC mass-mass) of imidacloprid and its main metabolites in soil, sunflower heads and seeds, wax, honey and pollen completed the study. Also, honey and pollen samples were analyzed to determine the sunflower pollen content in the hives. No residues of imidacloprid or of its structurally related metabolites olefin-imidacloprid and hydroxy-imidacloprid were detected (>1.5 m g/kg) in any of the components of the beehives 10 days after their exposure to the treated sunflower. The populations from treated and control hives presented no significant differences in their development regarding pollen entrance and pollen in the hives, nectar and mortality. However, treated hives were more productive in terms of average weight, honey production, foraging activity, worker brood and comb foundation probably due to the better physiological state of the treated crop. A high proportion (20%) of sunflower pollen in the honey and pollen samples obtained after the exposure to sunflower plots in control and treated hives, revealed that bees foraged actively on the sunflower. No side
effects were observed, in the short (10 and 24 days) or in the long-term
(226 days) analysis, on the hives exposed to the sunflower plot treated
with imidacloprid. The development of the hives or the individual bees
was not affected by their exposure during bloom to sunflower plants
originated from seeds treated with Gaucho®, under the conditions
of the trial.
|
|||||||||||||||||||||||||||||
