Author(s):

MR Bajiya and DP Abrol

Abstract: The effect of direct spray of insecticides on mortality of honeybee, Apis mellifera L. (Hymenoptera: Apidae) on mustard crop (Brassica napus) cultivar DGS-1 were studied at Jammu (India). Under field conditions the application of methyl-demeton resulted in 100 per cent bee mortality within one hour of spraying followed by imidacloprid (76.5, 100 per cent), acetamiprid (55.0, 62.5 per cent), diamethoate (47.5, 59.00 per cent) and thiamethoxam (42.5, 51.5 per cent) during 2014-15 and 2015-16 respectively. However, the per cent mortality of honey bee was not observed in treatment of control. Toxicity order of insecticides were methyl-demeton > imidacloprid > acetamiprid > diamethoate > thiamethoxam. After 3 hours of spraying the mortality was 100 per cent of methyl-demeton and imidacloprid followed by acetamiprid (77.5, 80.0 per cent), diamethoate (70.0, 79.0 per cent) and thiamethoxam (50.0, 56.5 per cent) whereas no mortality was observed in control treatment. Similar trend was obtained in all the treatments but with increased per cent bee mortality after 7 hours of spraying. After 12 and 24 hours of spraying the mortality was 100 per cent for all the treatments except thiamethoxam, which recorded (99.0, 97.5 per cent) during 2014-15 and 2015-16 respectively. It is thus evident that methyl-demeton followed by imidacloprid, acetamiprid, and diamethoate were more toxic to the honey bees forager and thiamethoxam having insecticidal properties was found to be less toxic of honey bees forager. Statistical analysis of the data revealed that effects of different insecticides at different hours of treatment on mortality of bees were highly significant.

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