Author(s):

Harish Kumar Sharma, Budhi Ram, Kiran Rana and Meena Thakur

Abstract: The decline of honeybees is a current cause of concern globally. A major factor implicated in their decline is exposure to agricultural chemicals, particularly neonicotinoid insecticides. Here, we assess the effects of neonicotinoids on honey bees mortality as they foraged on treated mustard bloom under field and semi field conditions. Neonicotinoid insecticides were sprayed on mustard at 50 percent bloom under field (thiamethoxam 0.1g/l) and semifield (thiamethoxam 0.1g/l and imidacloprid 0.3ml/l) conditions. The results obtained under semifield conditions showed significantly higher mortality on 1^st and 2^nd day after spray of thiamethoxam (293 and 231.83 bees/DBT/day) and the same trend was also recorded in imidaclprid (70.17 and 74 bees) spray in comparision to control (4.17 and 9.83). The mortality in both the insecticidal treatments reduced significantly after 3^rd day of spray, suggesting avoidance of foraging on treated crop by honeybees. Similarly under field conditions, the average bee mortality of A. mellifera was significantly higher on 1^st (112.50 bees/DBT/day) 2^nd (112 bees) and 3^rd day (46.33 bees) after spray in comparison to mortality observed in control. The overall mortality of A. mellifera exposed to the insecticidal treatments under both the conditions was recorded higher in comparison to control. These data demonstrate that there is a risk to honey bees from systemic residues in nectar and pollen following the spray of neonicotinoids during flowering period.

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