Short and long term side-effects on honeybees of imidacloprid in apple orchards

In order to evaluate the side effect of neonicotinoids on honey bees, two areas of apple orchards were selected in Trentino region, in which two different pest management strategies were applied: one based on the insecticide imidacloprid and the other on the insecticide flonicamid. Two localities within each area have been fixed, at least 1.5km far from each other, and in each locality 4 hives have been placed at the beginning of apple flowering. Every week up to three weeks after the insecticide application a complete set of data have been recorded on all 16 hives: weight of hive (colony), bee mortality (dead bees on underbasket), consistence of the colony, presence of the queen, eggs etc. Also pollen collected by bees during apple flowering and after the insecticide application was analyzed. After the end of field test bee colonies were transferred to a stable apiary and the vitality of the colonies was recorded every two weeks up to the overwintering of bee colonies and up to the spring awakening. Data obtained in this work showed higher mortality in the underbasket, a reduction of hive weight and higher queen mortality in those hives where imidacloprid was applied. Pollen analysis showed a high percentage of apple pollen after insecticide application. These preliminary results should be confirmed by further data.