In the study "Viability of colonies of honey bees exposed to sunflowers born from seeds treated with the neonicotinoids thiamethoxam and clothianidin" carried out by the National Institute of Agricultural and Food Research and Technology (INIA) and the Universities of Córdoba and Almería, and recently published in the scientific journal Chemosphere, no significant differences were found between colonies of bees exposed to sunflowers treated with neonicotinoids and those not exposed to these treatments

The objective of the large-scale field study, which has been carried out during the first year (2015-2016 campaign and with a duration of 3 years) in four Spanish regions: Andalusia, Castilla-La Mancha, Extremadura and Madrid, was broaden knowledge about the exposure of honey bees that pebble sunflowers born from seeds treated with the systemic neonicotinoids thiamethoxam (Syngenta) and clothianidin (Bayer). The use of these insecticides has been restricted in the EU since 2013 and on 27 April these restrictions on use were confirmed and extended by the European Commission, despite the most recent risk assessment reports for EFSA bees. European Food Safety Authority).

"The implementation of field studies with bees is really complicated, that explains why they are so scarce in relation to laboratory studies. However, it is the field studies that can provide realistic information of higher quality, "says José Manuel Flores, professor of the zoology department of the University of Córdoba and responsible for the biological part of the study.

"To evaluate the possible effects of the neonicotinoid residues, the sunflower plots were chosen so that they were as isolated as possible from other flowering crops, from other plant species that could attract bees and from the various treatment groups. each replica (a distance of 2 km when possible), and by analyzing the origin of the honey we were able to confirm that the exposure was indeed to the sunflower crops. The hot and dry weather conditions and the limited availability of other floral resources for bees during the summer, which is when sunflowers tend to bloom, forced us to look for a particularly high degree of isolation ", explained José Manuel Flores.

These conditions and the withdrawal of the food reserves before installing the hives in the flowering experimental fields made it possible to test in this study the most unfavorable conditions that guarantee the maximum exposure of the bees, and even so, the researchers have not found significant differences in the evolution of the hives between the control plots (untreated) and those treated with thiamethoxam or clothianidin, in key indicators for the health of honey bees, such as the vitality of the hives (number of adult bees per hive), the development of breeding, pollen and honey reserves, the presence and location of the queen, and the sanitary status of the hives.

The data of the study also highlights the need to take into consideration the initial vitality of the hives and the environmental conditions, two end-factors that have shown a clear indicence on the viability of the 72 beehives evaluated. "Under the conditions of southern Spain, it is likely that we should speak of a" summering "as well as a wintering, as evidenced by the fact that the highest percentages of depopulated colonies appeared before winter," the experts explain.